VLF observation during Leonid Meteor Shower-2002 from Kolkata

合集下载

(含答案)中学英语阅读短文之《火星探测》

（含答案）中学英语阅读短文之《火星探测》阅读短文并回答问题NASA’s Curiosity vehicle recently recorded the largest level of methane （甲烷）ever measured during its seven-year Mars mission.The discovery is exciting because the existence of methane gas could support the case for life on Mars.Methane has no color or smell.A special instrument on Curiosity’s Mars Science Laboratory recorded the increased gas level.The device,called a laser spectrometer,measures levels of chemical elements and gases in the Martian atmosphere.In addition to methane,the instrument can record levels of water and CO2.Nearly all the methane gas found in Earth’s atmosphere is produced by biological activity.It usually comes from animal and plant life.But it can also be formed by geological（地质的）processes,such as interactions between rocks and water.NASA said the increased methane was measured to be about21parts per billion by volume(ppbv).One ppbv means that if you take a volume of air on Mars, one billionth of the volume of air is methane.It was not the first time Curiosity has found methane gas in the Martian atmosphere.About a year ago,NASA announced that Curiosity had discovered sharp seasonal increases in the gas.This time,NASA said the measured methane gas level was clearly larger than any others observedin the past.NASA officials even temporarily stopped Curiosity’s other activities to investigate further.“It’s exciting because microbial（微生物的）life is an important source of methane on Earth,”NASA said in a statement announcing the discovery. However,Curiosity’s team carried out a follow-up methane experiment that showed a sharp drop in levels of the gas.The second examination found the level was less than one part per billion by volume.That number was close to the background levels Curiosity sees all the time. The rise and fall of the methane gas levels left NASA scientists with more questions than answers.The scientists are continuing to study possible causes for the sudden increase.The methane mystery continues.Curiosity does not have instruments that can exactly identify whether the source of the methane is biological or geological.One leading theory is that methane is being released from underground areas created by possible life forms that disappeared long ago.Even though Mars has no active volcanoes,scientists believe it is also possible that methane is being produced by reactions involving carbon materials and water.A clearer understanding of methane levels over time could help scientists determine where they’re located on Mars.Scientists hope this understanding will come as Curiosity continues to collect methane data in its search for possible life.1.Curiosity discovered.A.the largest methane gas level ever on MarsB.the existence of life on MarsC.the reason for the increased methaneD.interactions between rocks and water2.Why did NASA officials once stop Curiosity’s other activities?A.To seek possible life existing on Mars.B.To check the quality of Curiosity’s mission.C.To find seasonal increases in the methane gas.D.To further examine the methane gas level on Mars.3.What can we learn from the last three paragraphs?A.Causes for the change of methane have been proved by Curiosity.B.Curiosity has proved the location of methane by instruments.C.Scientists think underground materials’reactions may produce methane.D.Identifying the source of methane helps scientists search for possible life on Mars.4.The passage is probably taken from.A.a geography textbookB.a science newspaperC.a health magazineD.a travel brochure参考答案1–4ADCB生词及长难句1.NASA美国国家航空航天局2.Mars n.火星3.Curiosity’s Mars Science Laboratory“好奇号”火星科学实验室4.The device,called a laser spectrometer,measures levels of chemical elements and gases in the Martian atmosphere.句子主干：The device measures levels.参考译文：该装置叫做激光光谱仪，可以测量火星大气中化学元素和气体的含量。

火箭对科技的影响英语作文

Rocket technology has been a significant force in shaping the modern world, impacting various aspects of science,technology,and society.Heres a detailed look at how rockets have influenced technology:1.Space Exploration:Rockets have enabled humanity to explore beyond Earths atmosphere.The development of multistage rockets allowed for the escape from Earths gravity,leading to the historic Apollo missions that put humans on the moon.2.Satellite Communications:The ability to launch satellites into orbit has revolutionized global communication.Satellites provide television,radio,telephone,and internet services across the globe,connecting people in ways that were previously unimaginable.3.Global Positioning Systems GPS:GPS technology relies on a network of satellites in orbit,which are placed there using rockets.This system allows for precise navigation and location tracking,which is crucial for military,commercial,and civilian applications.4.Weather Forecasting:Weather satellites launched by rockets provide essential data for meteorologists to predict weather patterns and natural disasters,saving lives and resources through preparedness.5.Scientific Research:Rockets have been used to deploy scientific payloads that study the Earth,the sun,and other celestial bodies.This research has led to a deeper understanding of our universe and has contributed to advancements in various scientific fields.6.Technological Innovation:The development of rocket technology has spurred innovation in materials science,propulsion systems,and computer systems.These innovations have found applications in other industries,such as automotive,aerospace, and computing.7.Economic Growth:The space industry has become a significant economic driver, creating jobs and fostering technological advancements that benefit society.The commercialization of space through private companies like SpaceX and Blue Origin is further expanding this economic impact.8.International Cooperation:Rocket technology and space exploration have often been a platform for international collaboration.Projects like the International Space Station ISS bring together scientists and engineers from multiple countries to work on common goals.9.Inspiring Future Generations:The aweinspiring feats of rocketry have inspiredgenerations to pursue careers in science,technology,engineering,and mathematics STEM,ensuring a continuous pipeline of talent for future technological advancements.10.Mars Exploration and Beyond:Current and future rocket technologies are aimed at sending humans to Mars and potentially establishing a human presence beyond Earth. This represents the next giant leap in human exploration and survival.In conclusion,rockets have not only expanded our horizons by taking us to space but have also had a profound impact on technology and society.Their influence can be seen in everyday life,from the way we communicate to the way we understand our place in the cosmos.As rocket technology continues to evolve,its impact on our world will only grow.。

The Observation of Lunar Impacts. Part II

a r X i v :a s t r o -p h /0105226v 1 14 M a y 2001WGN,the Journal of the IMO 0:0(0)1The Observation of Lunar Impacts II.Costantino Sigismondi and Giovanni Imponente1.The detection of lunar impacts Although the lunar transient phenomena (LTP)have been observed since several tens of years,it is only recently that they reached the dignity of a scientiﬁc problem.Thanks to the eﬀort of some groups of scientists orchestrated by D.Dunham,it was possible to detect unambigously ﬁve ﬂashes onto the night side of the Moon [1]during the Leonids meteor shower of 1999.The opportunity to detect other impacts out of known active showers has been taken into account in our ﬁrst paper [2].Our goal there was to evaluate the possibility to have really observed one of them during the total eclipse of the Moon of January 21st 2000.A similar approach has been followed by Ortiz et al.[3]in order to explain another possible lunar impact observed on July 16th 1999.The technological possibility to monitor quite continously the Moon down to magnitudes fainter than the visible limit oﬀered by the CCD videocameras as well as their detection’s quantum eﬃciency larger than the classical photo plates have allowed to attain a rather big number of detected events during the last 12months.The publishing output at the same period was comparable to the whole activity till then [8].In this way,one can say that the Moon becomes the best laboratory for studying the meteor showers thanks to its large collecting area with respect to that one coverable by a single observer or even by a network of observers and of instruments devoted to that purpose.Moreover,during a meteor shower,in some conditions the Moon is visible in the horizon of diﬀerent places were the zenithal angular distance of the radiant is diﬀerent.This fact allows to perform a study of the large meteoroid population without considering the problems of the eﬀect of the radiant position in the sky nor the collecting volume eﬀect due to the brightness of the ﬁreballs that are visible at great distances and at low elevations.The latter case occurred inthe ﬁreballs’peak of 1998Leonids when it was frequently said that it was easier to look toward the horizon for looking more ﬁreballs [4].Finally the Moon is sampling a region ∼400000Km apart from the Earth and can intercept the stream in denser regions as happened in 1999Leonids.A wider knowledge of the entire structure of the stream can be achieved studying the streams both groundbased and looking the dark side of the Moon.Moreover,studies of the temporary sodium atmosphere of the Moon during meteor showers [5]can be joined to the studies of the meteor streams.2.The relation between kinetic energy and magnitude of a lunar impactDeveloping the approach of our ﬁrst paper [1]we consider the formula giving the amount of ra-diation,assuming the kinetic energy transforms entirely into radiant energy (luminous eﬃciency η∼1):W M =σT 4×A M The authors are aﬃliated with the Department of Physics,University of Rome “La Sapienza,”and ICRA,International Center for Relativistic Astrophysics,P le A.Moro 2,I-00185Rome,Italy.Costantino Sigismondi can be contacted at sigismondi@icra.it .2WGN,the Journal of the IMO0:0(0) where A M≈(M/ρ)2/3is the area of the incoming meteoroid and d Moon≈3.84×108m is theEarth-Moon average distance.In our previous work we assumed an impacting velocity of v=41km/s,obtained averaging the geocentric velocities of all known meteors showers.Here we extend to the whole spectrum of velocities,and we recover the behaviour of the equation for diﬀerent values of the mass. Moreover we take into account that the typical velocity for sporadic meteoroids is∼20÷30 Km/s[3,6,7].To calculate the visual magnitude,we must take into account that the eye is sensitive in a range of wavelengths between400nm-700nm,with a mean of550nm.It implies its maximum detection eﬃciency for a temperature of about5300K.The kinetic energy in calories(neglecting the melting heats and assuming the calorimetric equation for liquid water in all the range of impacting energies)corresponds to an increment of temperature for each gram of matter equal to∆T=v2×1000/2×4.18∼T.Therefore the temperature depends only on the velocity,here measured in Km/s.Calculating the value of W M as a function of velocity v and mass M we obtain typical values ofW M≈3×10−8W/m2,for a10g icy meteoroid impacting at41Km/s and producing a∆T≈2×105K.The eye can detect only∼1/2000000of suchﬂux,due to the ratio(5300/2×105)4,therefore the energy ﬂux in the visual range is W M≈1.5×10−14W/m2,i.e.,a magnitude1.5×10−14m=−2.5logWGN,the Journal of the IMO0:0(0)3 [3]J.Ortiz,P.V.Sada,L.R.Bellot Rubio,F.J.Aceituno,J.Aceituno,P.J.Gutierrez,U.Thiele,Nature405,22June2000,p.921.[4]R.Arlt,P.Brown,WGN27:6,December1999,p.278.[5]S.Verani,C.Barbieri,C.Benn,G.Cremonense,Planet.Space Sci.46,1998,p.1003.[6]Z.Ceplecha,Astronomy and Astrophysics286,1994,p.967.[7]P.Jenniskens,/˜leonid/guide/p1-magnitude.html1998,[8].,D.Dunham,.2000[9] D.Dunham,/lunarleonid/sizes.htm,2000.[11] D.Dunham,/lunar。

南京航空航天大学大一飞行英语lesson2课文

Lesson 2 Preflight PreparationThe Federal Aviation Regulations clearly indicate that “Each pilot in command shall, before beginning a flight, familiarize himself with all available information concerning that flight”. Unfortunately, no pilot could possibly be familiar with all information about a flight, and no matter how much preparation, there is no way to know when he or she has done all that can be done. However, the rule stands and pilots must determine how to live with it in the real world.Preflight planning goes a long way toward helping develop common sense into common practice. A few moments spent prior to each flight affords the pilot an excellent opportunity for a thorough preflight inspection that includes an equally thorough preflight weather briefing.The crew must determine the airworthiness of the aircraft and address any open issues before departure. The term “preflight” is typically used to describe the interior and exterior inspections of the aircraft, but in a general sense can be used to describe any activity involved with preparing the aircraft for departure to ensure safety. The aircraft inspection is usually divided among the cockpit crew and includes an exterior walkaround examination, interior cockpit setup, and systems checks. These preflight inspections are outlined in a checklist format which is used by the crew to aid in ensuring completeness and maintaining an acceptable level of standardization.Carelessly performed or disregarded preflight inspections have been the contributing cause of many accidents. Flights have been started, but sometimes not completed, because fuel or oil tanks were not checked, fuel caps were left off or loose, pitot systems were covered or blocked, gust locks were left on, wheel skirts were jammed with mud, engine coolers were blocked by bird nests, or wings and other surfaces were covered by frost, snow and ice.The exterior walkaround preflight consists of a visual inspection in which the crewmember checks for obvious damage to the fuselage, engines, wings and flight control surfaces. Other important items include tire wear and pressure, brake wear indicators, absence of leaks or fluid on the ramp, condition of antennae, probes and lights, necessity for deicing, and any other factors which may affect the safe conduct of the flight. A typical walkaround inspection can take anywhere from 8 to 20 minutes depending on the size and condition of the aircraft (and the number of wheels/ tires).The pilot should examine the windshield and side windows for cracks and / or crazing. Crazing decreases visibility and a severely crazed window can result in near zero visibility due to light refraction at certain angles to the sun.The pilot should inspect for any signs of deterioration, distortion, and loose or missing rivets or screws, especially in the area where the outer skin attaches to the airplane structure.The pilot should look along the wing spar rivet line—from the wingtip to the fuselage—for skin distortion. Any ripples and/or waves may be an indication of internal damage or failure.-However, there are other preflight considerations, too. Be sure to consider your aircraft’s fuel capacity, consumption rate, and range vs. wind conditions of each flight, and give careful thought to endurance and fuel reserves well above the minimum required by the FAR’s.Review routing, minimum altitudes along the flight path, navigation aids, notices to airmen, alternate airports in the area, destination airport runway lengths, and the like. Learn as much as you can about your destination airport before you depart.Performance and flight characteristics of your aircraft are determined, to a large degree, by the plane’s maximum weight. Never exceed your aircraft’s maximum weight. An airc raft loaded beyond gross weight might be uncontrollable, or might not even fly at all.Know your useful load—the difference between empty weight and maximum gross weight—and remember that this weight includes the weight of the oil and fuel, baggage, and passengers. Do not forget that some aircraft will exceed their gross weight limits if all seats are occupied and full fuel is carried.Just as important as not exceeding the aircraft gross weight is to load the aircraft properly. Center of gravity limits are becoming more crucial with larger-capacity aircraft. Know how to determine the c.g. location for various loads and configurations of your aircraft.Required runway lengths for landing and taking off might vary considerably with changes in field elevation, outside air temperature, aircraft load, and runway surface. To avoid running out of runway, consult your pilot’s operation handbook for the distances required to make a takeoff or landing under the conditions that exist at the time of the operation. Many pilots add a safety factor of 50 percent or more just to be sure.Remember that mixture, power, and rpm settings vary fuel consumption considerably. Fuel gauges might be inaccurate. Think of your aircraft’s endurance in terms of the actual fuel u sed versus the flight time. Remember a headwind or a tailwind can significantly shorten or lengthen the actual fuel range. Always provide for fuel reserves. Hundreds of aircraft have run out of fuel in the traffic pattern or in sight of the airport.According to the NTSB, many other accidents caused by pilot error involve pilots who do not know their aircraft’s operational numbers. Too fast, too slow, stall/spin, below engine-out speed, exceeded structural limit speed, loss of control in turbulence, out of c.g. limits, field too short for aircraft load and conditions, landed fast, or stalled on approach are just a few of the accident causes attributed to pilots who just didn’t know “the numbers” for their aircraft.(Note: A stall occurs when th e smooth airflow over the airplane’s wing is disrupted, and the lift degenerates rapidly. This is caused when the wing exceeds its critical angle of attack. This can occur at any airspeed, in any attitude, with any power setting.)To examine more closely just one of those factors, remember that controlling speed and using the correct speeds directly affect both your longevity and that of your aircraft. High speeds in turbulence or rough air might damage or destroy the aircraft structure. Too slow a speed might cause a stall, spin, or undershoot on landing. Knowing your best engine out-glide speed and best climb speed might mean the difference between you making the airport or ending up in the trees.Among the more important speeds to memorize include the various stall speeds, recommended approach speed, best rate and angle of climb speed, best glide speed, maneuvering (rough air) speed, maximum never-exceed speed, and gear and flap extension speeds. Remember, stall speeds increase measurably with angle of bank and weight increases.Of course, one of the most important elements in developing good flight safety is you. Establish a set of safe standards and limitations to which you can confidently adhere. Then stick to them, modifying the limitations only as you gain confidence and experience.New Wordsinspection n. 检查disregard v. 不理，忽视contribute v. 贡献，起作用gust n. 阵风frost n. 霜，冰冻consumption n. 消耗（fuel consumption）endurance n. 续航力，持续性alternate adj./n. 备降机场；备降的exceed v. 超过；飞过（规定界限）；超出gross adj.总的，毛重的crucial v.重要的configuration n. 形态;造型inaccurate adj. 有错误的，不准确的undershoot n./ v. 目测低，未达跑道着陆extension n. 延长，延期establish v.建立，制定adhere v. 遵守modify v.修改tank n.油箱pitot n. 空速管，全静压管block v.堵塞capacity n. 容量；能力range n. 航程；距离fuel n. 燃料；燃油reserve n./v. 预定；储备gravity n. 重力field n. 机场；领域elevation n. 标高；海拔gauge n. 仪表headwind n. 逆风，迎风tailwind n. 顺风glide v./n. 滑行；滑翔maneuver n. 机动动作gear n. 起落架；齿轮flap n. 襟翼；减速板；阻力板retract v. 收起，缩回ramp n. 停机坪antenna n. 天线windshield n.风挡crack v. 开裂，产生裂纹craze v. 产生细微裂纹throttle n. 油门panel n. 控制板，操纵盘pedal n. （脚）蹬，踏板lever n. 手柄；杆display n. 显示器indicator n. 指示器gyroscope n. 陀螺；陀螺仪deteriorate v. （使）恶化distortion n.扭曲，变形rivet n. 铆钉screw n. 螺丝钉critical adj. 临界的；关键性的angle of attack 迎角buffet v. 冲击，抖动，颤振Expressionslive with 接受，学会适应prior to 在…之前be jammed with 塞满to a large degree 很大程度上in terms of 按照，在…方面run out of 用完end up 结束，告终stick to 坚持，信守NotesNTSB National Transportation Safety Board (美国国家运输安全委员会)EXERCISESI. Describe the given terms from the text in English.1. weather briefing2. block3. gust lock4. endurance5. fuel reserve6. fieldII. Answer the following questions after you have read the text.1. What does the preflight planning include according to the passage?2. What is the main cause of many accidents?3. Would you list some items that a preflight inspection must include?4. How could a pilot decide how much fuel he must have for a certain flight?5. What will happen if an aircraft is overloaded?6. What is the useful load?7. What factors should be taken into account when a pilot thinks of an aircraft’s endurance for a certain flight?8. What is the consequence if the aircraft fly at high speed in turbulence?9. Under what circumstances will stall speeds increase?10. What do you think is the most important element in ensuring flight safety after reading the passage?III Read the following paragraph aloud until you can say it in a natural way from your memory.In civil aviation, a contaminated runway is one that is covered in a relatively deep layer of water, slush, loose snow, ice or compacted snow. The direct effects on aircraft performance of such contaminants arise due to the additional drag of the contaminants on the tyres and the reduced braking friction available.The consequences are mixed. Takeoff and landing distances in pilot’s operating handbooks are based on paved, dry, and level runway conditions. A contaminated runway would considerably increase the overall takeoff roll. During the take-off ground run the extra drag on the wheels reduces the aircraft’s ability to accelerate, and longer runway length is required to accelerate to takeoff speed. During landing or aborted takeoff, the reduced braking friction and increased drag on the tyres act in opposition to one another. In this case, more effective use of thrust reverser, brakes, speed brakesand rudder pedals is required in order to avoid overrun. In addition, the presence of such contaminants can also affect severely the ground-handling capability of the aircraft, particularly in cross-wind conditions.To avoid running out of runway, look up your pilot’s operating manual for distance required to make a takeoff or landing under the conditions that exist at the time of the operation.IV Complete the following short passage by filling the blanks with the words given in the box.After the pilot is seated in the 1 ________ and prior to starting the engine, all items and materials to be used on the flight should be arranged in such a manner that they will be readily 2 ________ and convenient to use.Extra caution should be taken at night to assure the 3 ________ area is clear. Turning the rotating beacon ON, or flashing the airplane position lights will serve to 4 _________ persons nearby to remain clear of the propeller. To avoid excessive drain of electrical current from the 5 _________, it is recommended that unnecessary electrical equipment be turned OFF until after the engine has been started.After starting and before taxiing, the taxi or 6 ________ light should be turned ON. Continuous use of landing light with r.p.m power setting normally used for taxiing may 7 ________ an excessive drain on the airplane’s electrical system. Also, overheating of the landing light could become a problem because of inadequate 8 _________ to carry the heat away. Landing lights should be used as necessary while taxiing. When using landing lights, consideration should be given to not 9 ________ other pilots. Taxi slowly, particularly in congested area. If taxi lines are painted on the ramp or taxiway, these lines should be followed to ensure a proper path along the route.The before-takeoff and runup（试车）should be performed using the checklist. During the day, forward movement of the airplane can be 10 ________ easily. At night, the airplane could creep forward without being noticed unless the pilot is alert for this possibility. Hold or lock the brakes during the runup and be alert for any forward movement.V Listening PracticeTask 1 Listen to the statements and fill in the missing words in the blanks.1. For ground operation, flight ________________ duties have been organized in accordance with an area of responsibility concept.2. The captains and first officers have their ____________________.3. All steps have to be performed prior to each originating flight or following ____________________________________.4. Any lights, which are not illuminated during a system test, will be checked by _______. The appropriate preflight procedures will be performed from memory.5. ____________ are used only to verify that ______ items affecting safety have been accomplished.Task 2 Listen to the passage and fill in the missing words in the blanks.To obtain a briefing from the FSS 1 ____________________ you will have to furnish some tangible information about your flight route such as 2 _______________________and arrival timesat your points of landing.After ensuring that the highest features 3 ____________________ of each leg will be either below your desired altitude or well away from your line of flight, you decide upon levels of legs to the destination.Although 4 ___________________________ is not mandatory to receive a weather briefing, many pilots believe it is helpful to compute a preliminary 5 ___________________________ so that the briefer will give them the 6 _______________________ for their arrival time.Every flight, local or 7 __________________________, must begin with a thorough inspection of the airplane. Be sure all the required papers are 8 _____________________ the aircraft. You should also check the aircraft 9 _____________________________ to verify that the required inspections are 10_________.Task 3 Listen to the following passage and choose the best answer to each question.Key words: echo, PFD, malfunction, initiate1. a. John b. Tedc. both of themd. neither of them2. a. wind shear b. cross windc. false indication of PFDd. unknown reason3. a. The crew fixed the problem.b. The company sent the maintenance stuff.c. The local maintenance staff fixed the malfunction.d. The ground maintenance staff fixed the malfunction.4. a. The malfunction occurred.b. Another problem appeared.c. Everything looked perfectly.d. They brought maintenance personnel.5. a. A pleasant flight b. The brave captain.c. Problem finding.d. An adventurous flight.VI Translate the following sentences into proper English.1.储备燃油可用于等待、备降、复飞或是其他不可预见的情况。

备战高考英语名校模拟真题速递(江苏专用)专题06 阅读理解之说明文10篇(第六期)(含解析)

备战高考英语名校模拟真题速递(江苏专用)第六期专题06 阅读理解之说明文10篇（2024·江苏南通·模拟预测）Mark Temple, a medical molecular (分子的) biologist, used to spend a lot of time in his lab researching new drugs for cancer treatments. He would extract DNA from cells and then add a drug to see where it was binding (结合) along the chemical sequence(序列). Before he introduced the drug, he’d look at DNA combination on a screen to see what might work best for the experiment, but the visual readout of the sequences was often unimaginably large.So Temple wondered if there was an easier way to detect favorable patterns. I realized I wanted to hear the sequence,” says Temple, who is also a musician. He started his own system of assigning notes to the different elements of DNA — human DNA is made of four distinct bases, so it was easy to start off with four notes — and made a little tune out of his materials. This trick indeed helped him better spot patterns in the sequences, which allowed him to make better choices about which DNA combinations to use.Temple isn’t the first person to turn scientific data into sound. In the past 40 years, researchers have gone from exploring this trick as a fun way to spot patterns in their studies tousing it as a guide to discovery. And the scientific community has come to realize that there’s some long-term value in this type of work. Temple, who from that first experiment has created his own algorithmic software to turn data into sound, believes the resulting music can be used to improve research and science communication.So Temple decided to add layers of sound to make the sonification (可听化) into songs. He sees a clear difference between “sonification” and “musification”. Using sound to represent data is scientific, but very different from using creative input to make songs. The musical notes from DNA may be melodic to the human ear, but they don’t sound like a song you’d listen to on the radio. So when he tried to sonify the virus, he added layers of drums and guitar, and had some musician friends add their own music to turn the virus into a full-blown post-rock song.Temple sees this work as an effective communication tool that will help a general audience understand complex systems in biology. He has performed his songs in public at concert halls in Australia.1．What is Mark Temple’s purpose in turning DNA data into sound?A．To help him fight boredom.B．To develop his creative ability.C．To make his drug more powerful.D．To aid the process of his experiments.2．What can we learn about Temple’s system?A．Its effect remains to be seen.B．It failed to work as expected.C．It is too complicated to operate.D．It has produced satisfying results.3．Why did Temple try to make the virus sound like real music when sonifying it?A．To get rid of public fear of the virus.B．To show h1s talent in producing music.C．To facilitate people’s understanding of science.D．To remind people or the roe or Science in art creation.4．What does the text mainly talk about?A．Why scientists are turning molecules into music.B．How scientists help the public understand science.C．Why music can be the best way to present science.D．How music helps scientists conduct their research.（2024·江苏南通·模拟预测）Phonics, which involves sounding out words syllable (音节) by syllable, is the best way to teach children to read. But in many classrooms, this can be a dirty word. So much so that some teachers have had to take phonics teaching materials secretly into the classroom. Most American children are taught to read in a way that study after study has found to be wrong.The consequences of this are striking. Less than half of all American adults were efficient readers in 2017. American fourth graders rank 15th on the Progress in International Literacy Study, an international exam.America is stuck in a debate about teaching children to read that has been going on for decades. Some advocate teaching symbol sound relationships (the sound k can be spelled as c, k, ck, or ch) known as phonics Others support an immersive approach (using pictures of cat to learn the word cat), known as “whole language”. Most teachers today, almost three out of four according to a survey by EdWeek Research Centre in 2019, use a mix of the two methods called “balanced literacy”.“A little phonics is far from enough.” says Tenette Smith, executive director of elementary education and reding at Mississippi’s education department. “It has to be systematic and explicitly taught.”Mississippi, often behind in social policy, has set an example here. In a state once blamed for its low reading scores, the Mississippi state legislature passed new literacy standards in 2013.Since then Mississippi has seen remarkable gains., Its fourth graders have moved from 49th (out of 50 states) to 20th on the National assessment of Educational Progress, a nationwide exam.Mississippi’s success is attributed to application of reading methods supported by a body of research known as the science of reading. In 1997 experts from the Department of Education ended the “reading war” and summed up the evidence. They found that phonics, along with explicit instruction in phonemic (音位的) awareness,fluency and comprehension, worked best.Yet over two decades on, “balanced literacy” is still being taught in classrooms. But advances in statistics and brain imaging have disproved the whole-language method. To the teacher who is an efficient reader, literacy seem like a natural process that requires educated guessing, rather than the deliberate process emphasized by phonics. Teachers can imagine that they learned to read through osmosis(潜移默化) when they were children. Without proper training, they bring this to classrooms.5．What do we learn about phonics in many American classrooms?A．It is ill reputed.B．It is mostly misapplied.C．It is totally ignored.D．It is seemingly contradictory.6．What has America been witnessing?A．A burning passion for improving teaching methods.B．A lasting debate over how to teach children to read.C．An increasing concern with children’s inadequacy in literacy.D．A forceful advocacy of a combined method for teaching reading.7．What’s Tenette Smith’s attitude towards “balanced literacy”?A．Tolerant.B．Enthusiastic.C．Unclear.D．Disapproving.8．According to the author what contributed to Mississippi’s success?A．Focusing on the natural process rather than deliberate training.B．Obtaining support from other states to upgrade teaching methods.C．Adopting scientifically grounded approaches to teaching reading.D．Placing sufficient emphasis upon both fluency and comprehension.（2024·江苏泰州·一模）A satellite is an object in space that orbits around another. It has two kinds — natural satellites and artificial satellites. The moon is a natural satellite that moves around the earth while artificial satellites are those made by man.Despite their widespread impact on daily life, artificial satellites mainly depend on different complicated makeups. On the outside, they may look like a wheel, equipped with solar panels or sails. Inside, the satellites contain mission-specific scientific instruments, which include whatever tools the satellites need to perform their work. Among them, high-resolution cameras and communication electronics are typical ones. Besides, the part that carries the load and holds all the parts together is called the bus.Artificial satellites operate in a systematic way just like humans. Computers function as the satellite’s brain, which receive information, interpret it, and send messages back to the earth. Advanced digital cameras serve asthe satellite’s eyes. Sensors are other important parts that not only recognize light, heat, and gases, but also record changes in what is being observed. Radios on the satellite send information back to the earth. Solar panels provide electrical power for the computers and other equipment, as well as the power to move the satellite forward.Artificial satellites use gravity to stay in their orbits. Earth’s gravity pulls everything toward the center of the planet. To stay in the earth’s orbit, the speed of a satellite must adjust to the tiniest changes in the pull of gravity. The satellite’s speed works against earth’s gravity just enough so that it doesn’t go speeding into space or falling back to the earth.Rockets carry satellites to different types and heights of orbits, based on the tasks they need to perform. Satellites closer to the earth are in low-earth orbit, which can be 200-500 miles high. The closer to the earth, the stronger the gravity is. Therefore, these satellites must travel at about 17,000 miles per hour to keep from falling back to the earth, while higher-orbiting satellites can travel more slowly.9．What is Paragraph 2 of the text mainly about?A．The appearance of artificial satellites.B．The components of artificial satellites.C．The basic function of artificial satellites.D．The specific mission of artificial satellites.10．What is the role of computers in artificial satellites?A．Providing electrical power.B．Recording changes observed.C．Monitoring space environment.D．Processing information received.11．How do artificial satellites stay in their orbits?A．By relying on powerful rockets to get out of gravity.B．By orbiting at a fixed speed regardless of gravity’s pull.C．By changing speed constantly based on the pull of gravity.D．By resisting the pull of gravity with advanced technologies.12．Why do satellites in higher-earth orbit travel more slowly?A．They are more affected by earth’s gravity.B．They take advantage of rockets more effectively.C．They have weaker pull of gravity in higher orbits.D．They are equipped with more advanced instruments.（2024·江苏泰州·一模）The human body possesses an efficient defense system to battle with flu viruses. The immune system protects against the attack of harmful microbes (微生物) by producing chemicals called antibodies, which are programmed to destroy a specific type of microbe. They travel in the blood and search the body for invaders (入侵者). When they find an invasive microbe, antibodies attack and destroy any cell thatcontains the virus. However, flu viruses can be a terrible enemy. Even if your body successfully fights against the viruses, with their ability to evolve rapidly, your body may have no protection or immunity from the new ones.Your body produces white blood cells to protect you against infectious diseases. Your body can detect invading microbes in your bloodstream because they carry antigens in their proteins. White blood cells in your immune system, such as T cells, can sense antigens in the viruses in your cells. Once your body finds an antigen, it takes immediate action in many different ways. For example, T cells produce more antibodies, call in cells that eat microbes, and destroy cells that are infected with a virus.One of the best things about the immune system is that it will always remember a microbe it has fought before and know just how to fight it again in the future. Your body can learn to fight so well that your immune system can completely destroy a virus before you feel sick at all.However, even the most cautious people can become infected. Fortunately, medical scientists have developed vaccines (疫苗), which are weakened or dead flu viruses that enter a person’s body before the person gets sick. These viruses cause the body to produce antibodies to attack and destroy the strong viruses that may invade during flu season.13．Why does flu pose a threat to the immune system?A．Microbes contain large quantities of viruses.B．Antibodies are too weak to attack flu viruses.C．The body has few effective ways to tackle flu.D．It’s hard to keep pace with the evolution of viruses.14．What does the underlined word “antigens” refer to in Paragraph 2?A．The cell protecting your body from viruses.B．The matter serving as the indicator of viruses.C．The antibodies helping to fight against viruses.D．The substance destroying cells infected with viruses.15．How do vaccines defend the body against the flu viruses?A．They strengthen the body’s immune system.B．They battle against weakened or dead viruses.C．They help produce antibodies to wipe out viruses.D．They expose the body to viruses during flu season.16．Which of the following is a suitable title for the text?A．Antibodies Save Our Health.B．Vaccines Are Of Great Necessity.C．Infectious Flu Viruses Are Around.D．Human Body Fights Against Flu Viruses.（23-24高三下·江苏扬州·开学考试）A recent study, led by Professor Andrew Barron, Dr. HaDi MaBouDi, and Professor James Marshall, illustrates how evolution has fine-tuned honey bees to make quick judgments while minimizing danger.“Animal lives are full of decisions,” says Professor Barron. “A honey bee has a brain smaller than a sesame (芝麻) seed. And yet it can make decisions faster and more accurately than’ we can. A robot programmed to do a bee’s job would need the backup of a supercomputer.”Bees need to work quickly and efficiently. They need to make decisions. Which flower will have a sweet liquid? While they’re flying, they face threats from the air. While landing, they’re vulnerable to potential hunter, some of which pretend to look like flowers.Researchers trained 20 bees to associate each of the five different colored “flower disks” with their visit history of reward and punishment. Blue flowers always had sugar juice. Green flowers always had a type of liquid with a bitter taste for bees. Other colors sometimes had glucose (葡萄糖). “Then we introduced each bee to a ‘garden’ with artificial ‘flowers’. We filmed each bee and timed their decision-making process,” says Dr. MaBouDi. “If the bees were confident that a flower would have food, they quickly decided to land on it, taking an average of 0.6 seconds. If they were confident that a flower wouldn’t have food, they made a decision just as quickly. If unsure, they took on average 1.4 seconds, and the time reflected the probability that a flower had food.”The team then built a computer model mirroring the bees’ decision-making process. They found the structure of the model looked very similar to the physical layout of a bee brain. “AI researchers can learn much from bees and other ‘simple’ animals. Millions of years of evolution has led to incredibly efficient brains with very low power requirements,” says Professor Marshall who co-founded a company that uses insect brain patterns to enable machines to move autonomously, like nature.17．Why does Professor Andrew Barron mention “a supercomputer”?A．To illustrate how a honey bee’s brain resemble each other.B．To explain how animals arrive at informed decisions fast.C．To demonstrate how a robot could finish a honey bee’s job.D．To emphasize how honey bees make decisions remarkably.18．Which of the following can best replace “vulnerable to” underlined in paragraph 3?A．Easily harmed by.B．Highly sensitive to.C．Deeply critical to.D．Closely followed by.19．What influenced the speed of trained bees in making decisions?A．Their judgments about reward and punishment.B．Their preference for the colors of flower disks.C．Their confirmation of food’s presence and absence.D．Their ability to tell real flowers from artificial ones.20．What message does Professor James Marshall want to give us?A．The power of bee brains is underestimated.B．Biology can inspire future AI.C．Autonomous machines are changing nature.D．AI should be far more efficient.（23-24高三下·江苏扬州·开学考试）Are you frequently overwhelmed by the feeling that life is leaving you behind, particularly when you look through social media sites and see all the exciting things your friends are up to? If so, you are not alone.FOMO, or Fear of Missing Out, refers to the perception that other people’s lives are superior to our own, whether this concerns socializing, accomplishing professional goals or generally having a more deeply fulfilling life. It shows itself as a deep sense of envy, and constant exposure to it can have a weakening effect on our self-respect. The feeling that we are always being left out of fundamentally important events, or that our lives are not living up to the image pictured by others, can have long-term damaging psychological consequences.While feelings of envy and inadequacy seem to be naturally human, social media seems to have added fuel to the fire in several ways. The reason why social media has such a triggering effect is tied to the appeal of social media in the first place: these are platforms which allow us to share only the most glowing presentations of our accomplishments, while leaving out the boring aspects of life. While this kind of misrepresentation could be characterized as dishonest, it is what the polished atmosphere of social media seems to demand.So how do we avoid falling into the trap of our own insecurities? Firstly, consider your own social media posts. Have you ever chosen photos or quotes which lead others to the rosiest conclusions about your life? Well, so have others and what they’ve left hidden is the fact that loneliness and boredom are unavoidably a part of everyone’s day-to-day life, and you are not the only one feeling left out. Secondly, learn to appreciate the positives. You may not be a regular at exciting parties or a climber of dizzying peaks, but you have your health, a place to live, and real friends who appreciate your presence in their lives. Last of all, learn to shake things off. We are all bombarded daily with images of other people’s perfection, but really, what does it matter? They are probably no more real than the most ridiculous reality TV shows.21．What can frequently experiencing FOMO lead to?A．Harm to one’s feeling of self-value.B．A more satisfying and fulfilling social life.C．Damage to one’s work productivity.D．Less likelihood of professional success.22．What does the author suggest in the third paragraph?A．The primary reason for FOMO is deeply rooted in social media.B．Our own social media posts help us feel much more confident.C．People who don’t share posts on social media are more bored.D．Social media’s nature enhances envious feelings and self-doubt.23．Why does the author mention reality TV shows in the last paragraph?A．To emphasize how false what we see on social media can be.B．To indicate how complicated social media has turned to.C．To figure out how popular and useful social media has been.D．To point out how educational value reality TV shows reflect.24．Which is the best title for the text?A．Myths and misconceptions about FOMO B．FOMO: what it is and how to overcome itC．How FOMO is changing human relationships D．We’re now all in the power of “FOMO addiction”（23-24高三上·江苏泰州·阶段练习）While Huawei’s official website does not call Mate 60 Pro a 5G smartphone, the phone’s wideband capabilities are on par with other 5G smartphones, raising a related question: As a leader in 5G technology, has Huawei managed to develop a 5G smartphone on its own?The answer is not simple. Huawei, as a pioneer in global 5G communication equipment, has played a leading role in the commercialization of 5G technology, with its strong system design and fields such as baseband chips (基带芯片), baseband processors and 5G modems.However, basebands and modems are not the only aspects that define 5G wireless communication. The stability and high-quality signals of a 5G smartphone also depend on other critical components such as RF transceivers (射频收发器) and RF front ends and antennas (天线) . These components are largely dominated by four US high-tech giants—Qualcomm, Avago Technologies, Ansem and Qorvo—which account for a surprising global market share.Huawei has faced significant challenges in getting critical components because of the sanctions imposed by the United States which are primarily responsible for the inability of the Chinese company to launch 5G smartphones in the past three years. However, Mate 60 Pro, despite not being labeled a 5G device, exhibits mobile network speeds comparable to Apple’s latest 5G-enabled devices, offering a stable communication experience. This suggests Huawei has, over the past three years, overcome the 5G development and production limits due to the US sanctions by cooperating with domestic partners, and establishing an independent and controllable stable supply chain.Considering that Huawei has not explicitly marketed this device as a 5G smartphone, it is possible that it isyet to fully overcome some key core technological and componential shortcomings. For the time being, we can consider Huawei’s Mate 60 Pro as 4.99G. But when combined with the satellite communication capabilities of Mate 60 Pro, it is clear Huawei has been trying to find more advanced wireless communication solutions for smartphones and making significant progress in this attempt. This should be recognized as a remarkable endeavor, even a breakthrough.25．What do the underlined words “on par with” mean in Paragraph 1?A．as poor as.B．as good as.C．worse than.D．better than.26．Why was it tough for Huawei to develop a 5G smartphone three years ago?A．Its system design and fields needed to be updated.B．It only focused on the commercialization of 5G technology.C．It was unwilling to cooperate with high-tech giants in America.D．It lacked critical components mainly controlled by US high-tech giants.27．What does Paragraph 4 centre on?A．The US sanctions.B．Critical components.C．Apple’s latest 5G-enabled devices.D．Progress in Mate 60 Pro.28．What is the text mainly about?A．Huawei faced with significant challengesB．Huawei’s Mate 60 Pro—a 5G smartphoneC．Huawei’s Mate 60 Pro—a remarkable breakthroughD．Huawei leading in global 5G communication equipment（23-24高三上·江苏无锡·期末）Blue-light-filtering glasses (滤蓝光眼镜) have become an increasingly popular solution for protecting our eyes from electronic screens’ near-inescapable glow — light that is commonly associated with eyestrain (眼疲劳). In recent years they’ve even become fashion statements that are recognized by celebrities and ranked in style guides. But a recent review paper shows such glasses might not be as effective as people think.The paper, published last week in Cochrane Database of Systematic Reviews, analyzed data from previous trials that studied how blue-light-filtering glasses affect vision tiredness and eye health. The study’s authors found that wearing blue-light-filtering glasses does not reduce the eyestrain people feel after using computers.“It’s an excellent review,” says Mark Rosenfield, a professor at the State University of New York College of Optometry, who was not involved in the study. “The conclusions are no surprise at all. There have been a number of studies that have found exactly the same thing, that there’s just no evidence that blue-blocking glasses have anyeffect on eyestrain.” He adds that the new review reinforces the fact that there is virtually no evidence that blue-blocking glasses affect eyestrain despite them being specifically marketed for that purpose. As for using blue-light-filtering eyeglasses for eye health, for now, Rosenfield says, “there’s nothing to support people buying them”.The strain we may feel while staring at our phone or computer screen too long is likely to be caused by multiple factors, such as bad habits or underlying conditions, an associate professor of vision science at the University of Melbourne, Downie says. She argues that how we interact with digital devices contributes more to eyestrain than screens’ blue light does. Changing the frequency and duration of screen usage and distancing one’s eyes from the screens might be more important in reducing discomfort, Downie says. She adds that people who experience eyestrain should see a doctor to assess whether they have an underlying health issue such as far-sightedness or dry eye disease.29．What can we know about blue-light-filtering glasses from the text?A．They can improve eyesight.B．They may not reduce eyestrain.C．They can promote eye health.D．They can help to cure eye diseases.30．What can we infer from paragraph 2?A．A great many professors were involved in the study.B．Blue-blocking glasses on the market are harmful to eyes.C．The finding of the study comes as a surprise to the public.D．Data from previous trials help the study a lot.31．What does the underlined word “reinforces” mean in paragraph 3?A．Denies.B．Opposes.C．Strengthens.D．Evaluates.32．What should we do if we suffer from eyestrain according to Downie?A．Wear blue-light-filtering glasses.B．Have an examination in the hospital.C．Stop staring at the screen for ever.D．Focus on the frequency of phone usage.（2024·江苏连云港·一模）Not all birds sing, but several thousand species do. They sing to defend their territory and croon (柔声唱) to impress potential mates. “Why birds sing is relatively well-answered,” says Iris Adam, a behavioral neuroscientist. However, the big question for her was why birds sing so much.“As soon as you sing, you reveal yourself,” Adam says. “Like, where you are and where your territory is.” In a new study published in the journal Nature Communications, Adam and her co-workers offer a new explanation for why birds take that risk. They may have to sing a lot every day to give their vocal (发声的) muscles the regular exercise they need to produce top-quality songs. To figure out whether the muscles that produce birdsongsrequire daily exercise, Adam designed an experiment on zebra finches-the little Australian songbirds.She prevented them from singing for a week by keeping them in the dark cage almost around the clock. Light is what galvanizes the birds to sing, so she had to work to keep them from warbling (鸣叫). “The first two or three days, it’s quite easy,” she says. “But the longer the experiment goes, the more they are like, ‘I need to sing.’” At that point, she’d tap the cage and tell them to stop singing.After a week, the birds’ singing muscles lost half their strength. But Adam wondered whether that impacted the quality of songs. When she played a male’s song before and after the seven days of darkness, she couldn’t hear a difference. But when Adam played it to a group of female birds, six out of nine preferred the song that came from a male who’d been using his singing muscles daily.Adam’s conclusion shows that “songbirds need to exercise their vocal muscles to produce top-performance songs. If they don’t sing, they lose performance, and their songs get less attractive to females.” This may help explain songbirds’ continuous singing.It’s a good rule to live by, whether you’re a bird or a human-practice makes perfect, at least when it comes to singing one’s heart out.33．According to Iris Adam, birds sing so much to ______.A．warn other birds of risks B．produce more songsC．perform perfectly in singing D．defend their territory34．What does the underlined word “galvanizes” in Paragraph 3 mean?A．Prepares.B．Stimulates.C．Forbids.D．Frightens.35．What do we know about the caged birds in the experiment?A．They lost the ability to sing.B．They strengthened their muscles.C．Their songs showed no difference.D．Their songs became less appealing.36．What may Iris Adam agree with?A．The songbirds live on music.B．The songbirds are born singers.C．Daily exercise keeps birds healthy.D．Practice makes birds perfect singers.（23-24高三上·江苏扬州·期末）Sometimes called “Earth’s twin,” Venus is similar to our world in size and composition. The two rocky planets are also roughly the same distance from the sun, and both have an atmosphere. While Venus’s cold and unpleasant landscape does make it seem far less like Earth, scientists recently detected another striking similarity between the two, the presence of active volcanoes.When NASA’s Magellan mission mapped much of the planet with radar in the 1990sit revealed an。

The multi-angle view of MISR detects oil slicks under sun glitter conditions

The multi-angle view of MISR detects oil slicks under sun glitter conditionsGuillem Chust ⁎,Yolanda SagarminagaAZTI-Tecnalia,Marine Research Division,Herrera kaia portualdea z/g,20110Pasaia,Spain Received 15February 2006;received in revised form 4September 2006;accepted 9September 2006AbstractWe tested the use of the Multi-angle Imaging SpectroRadiometer (MISR)for detecting oil spills in the Lake Maracaibo,Venezuela,that were caused by a series of accidents between December 2002and March 2003.The MISR sensor,onboard the Terra satellite,utilises nine cameras pointed at fixed angles,ranging from nadir to ±70.5°.Based upon the Bidirectional Reflectance Factor,a contrast function and a classification accuracy assessment,it is shown,for two images examined under sun glint conditions,that the MISR sensor provides a better capability for oil spill discrimination,than the single-view MODIS-250m data.Analysis of the multi-angle MISR red band indicates that oil spills appear with greater contrast in those view angles affected by sun glitter as a result of local changes in surface roughness caused by the hydrocarbons.Although limited by cloud cover,the capability of the MISR instrument for oil spill discrimination,together with its weekly temporal resolution and open data access,have the potential for improving the operational monitoring of oil releases.©2006Elsevier Inc.All rights reserved.Keywords:Multi-angle view;MISR;Coastal zones;Oil spill;Sun glitter1.IntroductionThe anthropogenic release of oil into the oceans from tankers,ships and pipelines may have significant ecological and socioeconomic impacts on coastal environments.A substantial part of oil pollution originates from operative discharges from ships (European Space Agency,2002;Pavlakis et al.,1996).Early detection of accidental or deliberate oil spills can prevent serious damages on littoral habitats and assist in the identi-fication of polluters.At present,there exist multiple instruments capable of detecting oil spills (Bedborough,1996;Brekke &Solberg,2005;Fingas &Brown,2000;Fingas &Brown,1997;MacDonald et al.,1993),using both space and airborne platforms:radar (SAR,SLAR),UV,microwave radiometers,photographic cameras,video cameras,electro-optical sensors within the visible and infrared,and laser fluorosensors.As the studies of Fingas and Brown (2000)and Brekke and Solberg (2005)conclude,each instrument has strengths and deficien-cies,so there is no single instrument that is best at detecting spills but rather multiple sensors are needed to provide the best discrimination.Active sensors such as Synthetic ApertureRadar (SAR),have been used commonly for ocean pollution detection (e.g.DiGiacomo et al.,2004;Gade &Alpers,1999);they are preferred to optical sensors due to their all-weather and all-day capabilities (Brekke &Solberg,2005).However,SAR data have also several disadvantages:1)there is generally no daily sampling on a routine basis,2)their application to oil spill detection is limited to a small range of wind speed (1.5–6m/s,Liu et al.,2000;at high wind speeds,N 10m/s,few oil spills can be detected in the SAR images,Gade et al.,2000);likewise,the wind conditions can also limit the use of optical sensors since high winds mix the oil into the surface waters,thus removing its presence as a surface slick;3)features such as phytoplankton and freshwater slicks may have similar appearance as oil slicks on SAR,which results in ambiguous detection of the oil itself (Lin et al.,2002),and 4)the images may be expensive to purchase.Although optical sensors are affected by cloud cover,they have the advantage of permitting the discrimination between algal blooms and oil spills,based on multispectral information (Brekke &Solberg,2005).For instance,the Visible and Near Infrared (VNIR)bands of MODIS have been shown to be effective in detecting oil slicks in Lake Maracaibo,Venezuela (Hu et al.,2003),although oil reflects particularly well in the thermal infrared portion of the spectrum (Salisbury et al.,1993).Remote Sensing of Environment 107(2007)232–239⁎Corresponding author.Tel.:+34943004800;fax:+34943004801.E-mail address:gchust@pas.azti.es (G.Chust).0034-4257/$-see front matter ©2006Elsevier Inc.All rights reserved.doi:10.1016/j.rse.2006.09.024Remotely sensed land surface reflectance has been shown to depend upon changing sun and sensor viewing geometry.This dependence,termed the Bidirectional Reflectance Distribution Function(BRDF),is highly anisotropic for volumetric targets such as atmospheric aerosols and vegetation.Oceanographic features can also manifest anisotropy,and this phenomenon can be highlighted under sun glitter conditions.Sun glitter involves the direct reflection of sunlight from the water surface.The presence of glitter in an image has been considered often to represent a serious data loss.Conversely,the acquisition of imagery containing areas dominated by sun glitter can,in certain circumstances,be of considerable value(Khattak et al., 1991;MacDonald et al.,1993).This is the case of surface wind speed(Cox&Munk,1954),oceanic internal waves(Matthews, 2005),shallow water bottom topography(Hennings et al., 1994)and river plume frontal boundaries(Matthews et al., 1997).Furthermore,water surfaces affected by sun glitter often manifest brightness reversal between two different views,in which relatively bright features at one angle appear dark in the other view.Such a region of brightness reversal can be indica-tive of a locally rough or smooth surface texture(Matthews, 2005),this may be found,for example,in the surroundings of internal waves or ship wakes.The optical response of the state of the sea surface roughness can be described by either the BRDF,or by the contrast distribution function(Otremba& Piskozub,2001).The need for multi-view observations has led to the incorporation of such measurements in several spaceborne missions(Asner et al.,1998)such as the Advanced Spaceborne Thermal Emission and Reflection Radiometer(ASTER),Multi-angle Imaging SpectroRadiometer(MISR),POLarization and Directonality of the Earth's Reflectance(POLDER),and the Advanced Land Observing Satellite(ALOS).In this contribution,the use of the Multi-angle Imaging SpectroRadiometer(MISR)is compared to the MODIS bands, at250m,for detecting oil spills in Lake Maracaibo,a coastal lagoon connected to the Gulf of Venezuela.Between December 2002and March2003,oil companies operating in the Lake Maracaibo suffered a series of accidents,which led to extensive oil spills.The detection of oil marine pollutants by the MISR has not been investigated extensively;this is despite a short Note which appeared on this particular issue by the Jet Propulsion Laboratory(NASA,/ gallery/galhistory/2003_may_21.html).This omission is not surprising,since the multi-angle view of MISR was designed mainly for distinguishing different types of atmospheric particles(aerosols),cloud geometry,land surface covers,and for use in the construction of3-D models(Diner et al.,1998). Specifically,the questions addressed here are:which MISR view angles are the most appropriate to detect oil-contaminated waters?and at which sunlight conditions?Likewise,can the multi-angle measurements enhance the oil discrimination in relation to a single-angle optical imager?2.MISR and MODIS imagery of oil slicksThe MISR sensor consists of nine pushbroom cameras,one viewing the nadir(vertically downward)direction(designated An)and four each viewing the forward and backward directions along the spacecraft ground track,labelled Df,Cf,Bf,Af,and Aa,Ba,Ca,Da,respectively.The corresponding viewing zenith angles are:70.5°(Df,Da),60°(Cf,Ca),45.6°(Bf,Ba),26.1°(Af,Aa)and0°(An).The overall time delay,between the Df and Da cameras,is7min.It observes the Earth in four visible and near infrared(NIR)spectral bands(446,558,672,and 866nm),with a cross-track ground spatial resolution of275m–1.1km.Only images sampled at medium-resolution(275m) were used in this study,i.e.the red band(672nm)at all nine view angles,and the four spectral bands at nadir view.The MISR swath width is380km(cross-track).The operational data products from MISR are described in Bull et al.(2005).The medium-resolution MISR radiance imagery(Level 1B2),from1December2002to9March2003,has been examined for Lake Maracaibo(Fig.1).The location of spills in MISR images was extracted from the studies undertaken by the Jet Propulsion Laboratory(NASA),with MISR(/gallery/galhistory/2003_may_21.html);like-wise,by Hu et al.(2003)who had identified already oil spills in the Lake with MODIS-250m data,acquired on the same dates,and used airborne photography for ground truth.The spills dispersed in the Lake as an oil film floating on the surface. Of the19image sets available for this period(obtained from the NASA Langley Research Center Atmospheric Sciences Data Center),images were selected that were free of clouds.Amongst these images,the most apparent oil spill patches were visually identified in those collected during December2002and January 2003(26/12/02,4/01/03,20/01/03and27/01/03),using the 275-m resolution red band.Finally,multiple angle analysis was performed on the image sets acquired on26December2002and 20January2003(Fig.1),which presented several oil spills and optimal cloud cover conditions.The corresponding MODIS images acquired on these two dates have been analysed also,for comparative purposes.The MODIS sensor aboard the Earth Observing System(EOS) satellites Terra and Aqua,provides a morning and afternoon view with global,near-daily repeat coverage.Such data are distributed by the Land Processes Distributed Active Archive Center(U.S.Geological Survey Center for Earth Resources Observation and Science).The Level1B calibrated-radiances of MODIS band1(645nm,red)and band2(856nm,near infrared)were used.These bands have a spatial resolution of 250m.The MODIS swath width is2330km.The observational geometry parameters of the two selected dates involved in sun glitter conditions were contained in the corresponding products(the general conditions are described in Hennings et al.,1994,and in Matthews,2005).The geometric parameters are defined as follows(see also Bull et al.,2005). Solar zenith is the angle between the+z axis(which points into the earth,in the direction opposite the ellipsoid normal)and a vector anchored at the ground point extending into the earth in the direction of photon travel from the sun.Solar azimuth is the angle measured clockwise from the local north vector to the projection onto the x,y plane of the photon travel direction vector.This“photon travel azimuth”convention differs from the familiar“look azimuth”by180°.Camera zenith is the angle233G.Chust,Y.Sagarminaga/Remote Sensing of Environment107(2007)232–239between the −z axis and the “camera vector ”,which is anchored at the ground point and is directed toward the camera in the direction of photon travel.Camera azimuth is the angle measured clockwise from the local north vector to the projection onto the x ,y plane of the camera vector.For the images analysed,solar zenith (ζ)and azimuth (Φ)angles were:ζ=38.2°,Φ=330.9°(26/12/2002),and ζ=36.8°,Φ=324.5°(20/01/03).For Af view,the camera azimuth angles were 340.3°and 16.2°on 26/12/02and 20/01/03,respectively;the camera zenith angles were:30.1°and 28.5°on 26/12/02and 20/01/03,respectively.Near-surface wind speeds were low to moderate:4.4m/s (26/12/2002)and 5.6m/s (20/01/03);as measured byQuikSCATFig.1.Series of MISR (672nm)images of a portion of the Lake Maracaibo taken by cameras viewing 0°(camera An),26.1°forward (Af),and 45.6°forward (Bf).Black arrows on the An camera image indicate the oil spills used in the BRF analysis in the present paper;the white arrows indicate other main slicks used in the validation of supervised classifications.The inset image shows the location of Lake Maracaibo within the coastal region of the Gulf of Venezuela.234G.Chust,Y.Sagarminaga /Remote Sensing of Environment 107(2007)232–239(Level3Daily,0.25×0.25°Gridded Ocean Wind Vectors,JPL SeaWinds Project).These wind values fall within the range at which hydrocarbons dampen sea waves.3.Bidirectional reflectance factor and discrimination of oil slicksRadiance values were converted initially to the top-of-atmosphere bidirectional reflectance factor(BRF),for each band and view angle.The Bidirectional Reflectance Factor (BRF)is defined as the observed radiance divided by the radiance from a perfect Lambertian reflector,under conditions in which the illumination is from a single direction(Martonchik et al.,1998).We used the following equation to calculate the top-of-atmosphere BRF(see Bull et al.,2005):BRFð−l;l0;U−U0Þ¼p Lð−l;l0;U−U0Þd D2E0;b;where L is the measured radiance from MISR Level1B2radi-ance product,μis the cosine of viewing zenith angle,μ0is thecosine of solar zenith angle,Φ−Φ0is the difference betweensolar and viewing azimuth angles,D is the approximate dis-tance,in astronomical units,between the centre of the Earth andthe centre of the Sun,at the time that the MISR observes the firstpixel in the swath,and E std0,b(W m−2μm−1)is the standardised band-weighted solar irradiance.The BRF sampled within the oil slick patches and theirsurroundings(oil-free water)were analysed at different viewangles(i.e.9cameras)within the red band,and they have beencompared with glitter conditions and glitter angle.The BRFsamples were extracted by selecting visually all pixels withinthe oil slick patches,excluding boundary pixels,and unpollutedareas adjacent to each slick;one slick was chosen for each date(indicated in black arrows in Fig.1).The glitter conditions andglitter angle were contained in the corresponding productsdescribed in Bull et al.(2005),obtained also from the LangleyAtmospheric Data Center.Glitter conditions are represented bya binary mask image,providing a glitter contaminated/non-contaminated pixel information at1.1×1.1km.Glitter angle(°)is the angle between a vector from the observed point to thecamera and a vector pointing in the specular reflection direction;it is provided at17.6×17.6km spatial resolution.The potential discrimination of oil pollutants,using MISRand MODIS-250m,has been assessed by1)a comparison ofradiance means between oil slick patches and their surroundings(using a contrast function and the Wilks'Lambda test)for eachspectral band at nadir,and for each view angle;and2)super-vised classifications and the associated accuracy assessment.The contrast function(Otremba&Piskozub,2001),at a givenwavelengthλ,is expressed by the following relationship:cðf r;U r;kÞ¼L pðf r;U r;kÞ−L cðf r;U r;kÞL cðf c;U r;kÞwhere L p(ζr,Φr,λ)is the upward radiance above the polluted sea surface in a direction defined by a zenith angleζr and an azimuth angleΦr,and L c(ζr,Φr,λ)is the upward radiance above the clean sea surface.The Wilks'Lambda is based on a discriminant analysis and tests the hypothesis that the means are equal across classes(i.e.polluted vs clean waters).Wilks' Lambda close to0indicates that the classes are different.A per-pixel supervised classification method based on maximum likelihood algorithm was used to assess the discrimination between the oil slicks and two types of oil-free water.These two types of unpolluted waters have been defined to cover the maximal range in radiances on the water state of the Lake,at red wavelengths;thus,Type1refers to relatively high radiance values and Type2refers to relatively low radiances.Two independent training sites have been created;one to calculate the statistics needed for the classification;the other to evaluate the reliability of classifications.Several slicks for each date were used for classification(indicated in black and white arrows in Fig.1).Prior to performing the classification process,the Jeffries–Matusita separability index(Thomas et al.,1987)was calculated between pairs of classes using the first training site set.As measures of classification accuracy,the producer's accu-racy(PA)and the user's accuracy(UA)for each class,were used (Stehman,1997).These accuracy measurements are derived from the confusion matrix which is created from the comparison between the classification and the verification data(a set of training sites independent of that used for the classification process).Several classifications were performed combining those MISR bands and cameras with higher discrimination potential, based on the Wilks'Lambda test;likewise,one classification with MODIS(using NIR and red bands).4.Results and discussionFig.1shows a portion of the images at different view angles acquired by the275-m resolution MISR red band(672nm)of a part of Lake Maracaibo on26December2002and20January 2003.On these two dates,oil slicks were identified mainly in the three views affected mostly by sun glitter(Fig.2c,d):nadir, 26°and46°forward,i.e.An,Af and Bf cameras,respectively. At nadir and46°forward,all the oil slicks appear as darker zones on the image.At26°forward,which is the view closest to the specular reflection on the two dates(Fig.2c,d),the oil slick appears brighter on26December2002.On20January2003, where the glitter angle(29.8°)is not as close to the specular angle as on26December2002(10.9°),the slicks to the north and east appear darker,whilst the central slick is less visible.As previously shown,the differences in sun glitter conditions between the two dates depend mainly upon the different solar azimuth angle(Δ=6.4°)and Af camera azimuth angle (Δ=35.8°).Two large oil slicks,one for each date(indicated with black arrows in Fig.1),have been selected subsequently for analysis, to extract BRF values,contrast function and Wilks'Lambda. For December2002,Fig.2a shows that the differences in the BRF values are greater for the Af and Bf cameras,in which calm water regions are expected to be affected maximally by sun glitter(Fig.2c).At the An view,the oil has also an im-portant contrast value(Table1).The Wilks'Lambda provides slightly different results;it indicates that Bf is the camera within235G.Chust,Y.Sagarminaga/Remote Sensing of Environment107(2007)232–239the red band that better discriminates polluted waters,followed by An;whilst Af,the closest to the specular reflection,is not as capable as An and Bf.Although the Wilks'Lambda test indicates that slicks can be discriminated statistically on all of the cameras,those which are far from the specular reflection have less discrimination potential.For January 2003,the oil slick shows maximal BRF differences in the Af and An cameras,followed by Bf (Fig.2b);this is in accordance to the sun glitter conditions (Fig.2d),high contrast and low Wilks'Lambda values (Table 1).For the two dates,both the contrast and the Wilks'Lambda indicates that NIR is the most appro-priate,amongst the four VNIR spectral bands at nadir,to discriminate oil slicks,this is followed by the red band in most of the cases (Table 1).The red and the NIR bands of MODIS have similar values of contrast and Wilks'Lambda compared to the corresponding bands of MISR's An camera (Table 1).These results indicate that the direct reflection of sunlight arrives from the oil-contaminated water at 26°view on 26December 2002.The oil-contaminated waters in that date man-ifest brightness reversal between the moderately near specular angles (nadir and 46°forward-looking view)and the very-near specular angle (26°view).Such regions of brightness reversal can be indicators of local roughness changes in surface texture (Matthews,2005);and,as is well known,oil slicks tend to dampen surface capillary waves,making the water smoother than the surrounding oil-free water.As a general rule,the optical contrast of an oil film on a sea surface,at specific wind conditions and at red wavelengths,depends on three domains of the glitter angle:1)at angles (N 40°)not affected by sun glitter,slicks are practically not detected;2)at angles (b 15°)very near to the specular angle,the slicks appear brighter than the unpolluted areas;and 3)at angles (15°–40°)moderately near to the specular angle,the slicks appear darker,since oil is more absorbing than the surrounding water.This is the case for December 2002,whilst for January 2003a brightness reversal is not present,because of higher sun glitter angles (N 15°).The threshold values of glitter angles indicated here are obtained from the two images;in order to estimate these thresholds with confidence,more images are needed.Since An,Af,and Bf were identified as the cameras with high discrimination potential,four classifications were performed,combining these cameras with spectral bands at nadir:1)An view (NIR and red bands);2)An (NIR and red),Af and Bf;3)An (4bands),Af and Bf;and 4)An (NIR and red),and all cameras excluding Af.By comparing the first two classifications,the contribution of multi-angle with respect to just the An view is tested.The third classification tests the joint contribution of spectral bands with multi-angle view.By excluding Af,thefourthFig.2.The top-of-atmosphere BRF values from the MISR (672nm)image within the oil slicks on the Lake present on (a)26December 2002and (b)20January 2003,compared with the surrounding clean water at different view angles.Error bars represent ±standard deviation.For December 2002,the oil and unpolluted patches contained 307and 206pixels,respectively;for January 2003,the oil and unpolluted patches contained 15and 243pixels,respectively.The glitter angle and glitter condition of the area affected by spills at the corresponding dates:(c)26December 2002;and (d)20January 2003.236G.Chust,Y.Sagarminaga /Remote Sensing of Environment 107(2007)232–239classification tests the effect of removing brightness reversal in the image set of 2003.The Jeffries –Matusita index indicates high separability between oil and clean water Type 1in all cases at the two dates,including MODIS (Table 2).Conversely,low values of separability index were found between the oil and clean water Type 2,in two of the cases:using An (red and NIR)for MISR,and red and NIR for MODIS.The classification accuracy assessment (Table 2)has revealed that the two classifications combining Af and Bf cameras with spectral bands in An produced high values of producer's (PA)or user's accuracy (UA)(higher than 81%for December 2002and higher than 70%for January 2003).The classification using only the red and NIR bands in An produced low accuracy values (PA or UA inferior to 50%).These latter values are similar to the corresponding classification of the MODIS bands.The classification using all cameras excluding Af produced higher accuracy values for the December 2002(PA=65%and UA=75%)than that of MODIS (PA=53%and UA=30%).This observation indicates that the varying appearance of spills as a function of view angles alone (without the presence of brightness reversal)can improve oil discrimination in comparison to a single-view optical imager.However,the presence of brightness reversal,in particular,enhances this discrimination potential.In the case of January 2003,the classification using all cameras excluding Af produced a low producer's accuracy value (46%);once again,this indicates the importance of the Af camera in oil discrimination.The general low accuracy determinations in January 2003,compared with December 2002,is due to the absence of brightness reversal;likewise,to the size of the oil patches.In January 2003,the oil patch was small and thin and,hence,the radiance value is affected by the neighbouring pixels.5.Conclusions and perspectivesThe findings of the present study show,at least for the two images examined here,that the 275m resolution MISR sensor provides a capability for oil spill discrimination in coastal environments which is better than MODIS-250m sensor under sun glint.The results of the MISR red band,at different angle views,indicate that oil spills appear in more contrast in those views affected by sun glitter.The changes in the radiance-related quantities,as a function of view angle,depend on the composition,density,and geometric structure of the reflecting surface (i.e.water state);they are exemplified by glitters,shadows,and volumetric scattering (Diner et al.,2005).The results obtained here enable the conclusions to be reached that,spectrally,oil slicks can be detected within the red band;this contrast is highlighted under glitter conditions,as a result of local changes in surface roughness caused by the presence of hydrocarbons.Dampening of water surface waves by oil slicks occurs at low to moderate winds,which were the prevailing conditions on the two dates discussed here.For the two sets of images examined,three domains of oil radiometric response as a function of view angle have been identified:1)at angles unaffected by sun glitter,slicks were not identified or appeared slightly darker than adjacent unpolluted areas;2)at angles affected by sun glitter,but moderately near to the specular direction,slicks appeared darker because they are more absor-bent than unpolluted waters;and 3)at the specular angle,or very near to,the slicks appeared brighter.The specific range of sun glitter angles which dictates the radiometric contrast depend on wind speed conditions (Otremba &Piskozub,2001).This phenomenon is well established in SAR imagery,where the presence of hydrocarbon smoothes water surface roughness and causes a reduction in the backscattering.The detection of oceanic surface films by MISR depends on the factorsTable 2Jeffries –Matusita separability index and classification accuracies of oil slicks vs clean waters combining different bands and cameras of MISR and MODIS-250m (spills of 26December 2002and of 20January 2003).Key,PA:Producer's accuracy;UA:User's accuracy;Clean 1:oil-free water type 1;and Clean 2:oil-free water type 2(see text for explanation)SensorBands and camerasDecember 26,2002January 20,2003Jeffries –Matusita PA UA Jeffries –Matusita PA UA Oil vs Clean 1Oil vs Clean 2Oil Oil Oil vs Clean 1Oil vs Clean 2Oil Oil MISRAn (NIR,red)1.990.5449.7121.88 1.870.5347.5829.49An (NIR,red),Af,Bf2.00 1.9698.3793.30 1.99 1.4870.63100.0An (NIR,red,green,blue),Af,Bf2.00 2.0081.58100.0 1.99 1.9173.6194.29An (NIR,red),all cameras excluding Af 1.99 1.9665.2075.34 1.97 1.9945.7282.55MODISNIR,red1.990.7953.4429.531.880.5677.1748.76Table 1Contrast values and Wilks'Lambda test in oil slicks in relation to the surroundings waters,on 26December 2002and 20January 2003,for 275-m spatial resolution MISR and MODIS-250m SensorBandCameraDecember 26,2002January 20,2003ContrastWilks'Lambda Contrast Wilks'Lambda MISRBlue An −0.0170.135⁎⁎−0.0230.755⁎⁎Green An −0.0520.073⁎⁎−0.0430.937⁎⁎NIR An −0.1650.044⁎⁎−0.1780.571⁎⁎Red Df 0.0500.360⁎⁎−0.0080.995Red Cf 0.0270.240⁎⁎−0.0220.958⁎⁎Red Bf −0.1720.046⁎⁎−0.0490.919⁎⁎Red Af 0.4200.238⁎⁎−0.2050.504⁎⁎Red An −0.0920.056⁎⁎−0.1020.761⁎⁎Red Aa 0.0420.408⁎⁎−0.0070.998Red Ba 0.0220.412⁎⁎−0.0030.999Red Ca 0.0230.569⁎⁎−0.0050.997Red Da 0.0330.691⁎⁎−0.0080.985⁎MODIS-250mRed –−0.0930.095⁎⁎−0.0990.690⁎⁎NIR–−0.1930.091⁎⁎−0.2170.464⁎⁎⁎0.001b p b 0.05;where p is the p -value associated to the Wilks'Lambda test.⁎⁎p ≤0.001.237G.Chust,Y.Sagarminaga /Remote Sensing of Environment 107(2007)232–239。

【资格考试】2019最新整理-职称英语理工类阅读判断模拟试卷4

——参考范本——【资格考试】2019最新整理-职称英语理工类阅读判断模拟试卷4______年______月______日____________________部门阅读下面的短文。

每篇短文后面都有七句话，请根据短文的内容判断这些话是正确、错误，还是在短文中没有提到。

每个试题计1分,共计7分。

The Northern LightsThe Sun is stormy and has its own kind of weather．It is so hot and active that even the Sun’s gravity cannot holdits atmosphere in check1! Energy flows away from the Sun toward the Earth in a stream of electrified particles that move at speeds around a million miles per hour2．These particles are called plasma，and the stream of plasma3 coming from the Sun is called the solar wind．The more active the Sun，the stronger the solar wind．The solar wind constantly streams toward the Earth，but don’t worry because a protective magnetic field surrounds our planet．The same magnetic field that makes your compass point north also steers the particles from the Sun to the north and south poles．The charged particles become trappedin magnetic belts around the Earth．When a large blast of solar wind crashes into the Earth’s magnetic field，the magnetic field first gets squeezed and then the magneticfield lines break and reconnect．4The breaking and reconnecting of the magnetic field lines can cause atomic particles called electrons trapped in the belts to fall into the Earth’s atmosphere at the poles．Asthe electrons fall to the Earth，they collide with gas molecules in the atmosphere，creating flashes of light in the sky．Each atmospheric gas glows a different color．Oxygen and nitrogen glows red and green and nitrogen glows violet-purple．As these various colors glow and dance in the night sky，they create the Northern Lights and the Southern Lights．Watching auroras is fun and exciting，but normally youcan only see them in places far north like Alaska and Canada．The movement of the aurora across the sky is usually slow enough to easily follow with your eyes but they can also pulsate，flicker，or even move like waves．During solar maximum，5 auroras are seen as far south as Florida，even Mexico! 6Auroras often seem to be very close to the ground，butthe lowest aurora is still about 100 kilometers above the ground，a distance much higher than clouds are formed or airplanes can fly．A typical aurora band can be thousands of kilometers long，a few hundred kilometers high，but only afew hundred meters thick．。

华北地区沙尘天气垂直气溶胶直接辐射强迫

中国环境科学 2020,40(12)：5169~5181 China Environmental Science 华北地区沙尘天气垂直气溶胶直接辐射强迫侯灿1,2,张峰3,黄勇1,2,吴文玉1,2,邓学良1,2,陶明辉4*(1.安徽省气象科学研究所,大气科学与卫星遥感安徽省重点实验室,安徽合肥 230031；2.寿县国家气候观象台,中国气象局淮河流域典型农田生态气象野外科学试验基地,安徽寿县232200；3.复旦大学大气与海洋科学系,大气科学研究院,上海 200438；4.中国地质大学(武汉)地理与信息工程学院,关键带演化实验室,湖北武汉 430074)摘要：利用CALIOP数据和SBDART(Santa Barbara DISORT Atmospheric Radiative Transfer)辐射传输模式研究了2013~2016年华北地区8d沙尘天气气溶胶及其直接辐射强迫垂直分布特征,分析了气溶胶垂直分布和光学特性对直接辐射强迫的影响.结果表明,气溶胶集中分布在地表及以上3km范围,其中纯净沙尘型和污染沙尘型气溶胶位于上层,污染大陆型气溶胶和烟雾位于下层.大气层顶、地表和大气层的日均气溶胶直接辐射强迫分别是-38.41~-88.44,-74.03~-225.86,9.06~137.42W/m2.0~8km高度范围气溶胶直接辐射强迫是负值,且随着高度的增加绝对值逐渐减小.气溶胶垂直分布对大气层顶、地表和大气层的直接辐射强迫影响较小,但对直接辐射强迫垂直分布影响较大,由气溶胶廓线差异造成的同一高度层气溶胶直接辐射强迫最大差值能达到31.18W/m2.气溶胶光学厚度和单次散射反照率对直接辐射强迫影响明显.消光能力相同时,吸收性气溶胶对短波太阳光的衰减作用大于散射性气溶胶,后向散射比例大的气溶胶大于后向散射比例小的气溶胶.关键词：气溶胶直接辐射强迫；垂直分布；辐射传输模式；华北地区；沙尘天气中图分类号：X513 文献标识码：A 文章编号：1000-6923(2020)12-5169-13Vertical distribution of aerosol direct radiative forcing in dust events over north China. HOU Can1,2, ZHANG Feng3, HUANG Yong1,2, WU Wen-yu1,2, DENG Xue-liang1,2, TAO Ming-hui4* (1.Anhui P rovince Key Laboratory of Atmospheric Sciences and Satellite Remote Sensing,Anhui Institute of Meteorological Sciences, Hefei 230031, China；2.Huai River Basin Typical Farm Eco-meteorological Experiment Field of China Meteorological Administration, Shouxian National Climatology Observatory, Shouxian 232200, China；3.Department of Atmospheric and Oceanic Sciences, Institute of Atmospheric Sciences, Fudan University, Shanghai 200438, China；boratory of Critical Zone Evolution, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430074, China). China Environmental Science, 2020,40(12)：5169~5181Abstract：Using CALIOP data and SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model, the vertical distribution of aerosols and their direct radiative forcing in 8 dusty days between 2013 and 2016 in north China were studied. The effects of vertical distribution and optical properties on aerosol direct radiative forcing were also analyzed. The results showed that, the aerosols are concentrated from the surface to 3km, in which the dust particles are in the upper layer, while polluted continental aerosols and smoke are in the lower layer. The daily mean of aerosol direct radiative forcing is in -38.41 ~ -88.44 W/m2 at the top of the atmosphere, and -74.03 ~ -225.86W/m2 at the surface and 9.06 ~ 137.42W/m2 in the atmosphere, respectively. The aerosol direct radiative forcing is negative at 0~8km, and the magnitude gradually decreases as altitude. Vertical distribution has little effect on the magnitude of direct aerosol radiative forcing, but exhibits great influence on its vertical characteristics. The maximum difference of aerosol direct radiative forcing at the same altitude caused by the difference of aerosol profile can reach 31.18W/m2. The influence of aerosol optical depth and single scattering albedo on aerosol direct radiative forcing is obvious. When the extinction ability is the same, the attenuation effect of absorbing aerosols or with large backscattering ratio on short-wave sunlight is greater than that of scattering aerosols or with small backscattering ratio.Key words：aerosol direct radiative forcing；vertical distribution；radiative transfer model；north China；dust events气溶胶在影响地球能量平衡和全球气候变化中起着重要作用,主要体现在气溶胶吸收、散射短波和长波辐射对气候产生直接影响[1-3],以及气溶胶作为云凝结核影响云微物理特性,如云滴数密度、云滴尺度和云生命周期等,对气候产生间接影响[4].气溶胶辐射强迫可以评估气溶胶对气候变化的影响程度.但众多的气候变化影响因子中,最不确定和亟待深入认识的是人类活动产生的气溶胶辐射影响[5].收稿日期：2020-04-19基金项目：国家重点研发计划专项(2016YFC0201900);安徽省重点研究与开发计划(202004b11020012);国家自然科学基金面上项目(41675003) * 责任作者, 教授,*************.cn5170 中国环境科学 40卷为减小估算气溶胶辐射强迫的不确定性,国内外实施了多个气溶胶观测计划,利用地基观测和卫星遥感手段得到气溶胶光学参数.然而,利用这些数据作为输入参数研究气溶胶辐射效应和气候效应仍具有很大的不确定性.气溶胶生命周期短,自身的物理化学性质时空分布变化大是原因之一,另一个重要原因是气溶胶垂直分布不均匀,难以参数化[6-7]. Meloni等[8]指出气溶胶垂直分布是估算气溶胶直接辐射强迫不确定性的最大来源之一.Chung等[9]估算出气溶胶垂直分布会对全球总气溶胶直接辐射强迫产生0.5W/m2的不确定性.针对这一现象,众多学者开展了大量研究工作,结果发现不同地区和种类的气溶胶垂直分布特征及其对直接辐射强迫的影响存在明显差异[10-14],且由于观测数据的限制,中国地区的相关研究不够充分.华北地区人口的大量聚集使得该地区的气溶胶尤其是人为气溶胶的含量一直居高不下[15].目前,华北地区已经是影响全国乃至全球的气溶胶辐射效应和气候效应不确定性的主要区域之一[16].本文以沙尘天气为切入点,筛选出2013~2016年华北地区(34°N~41°N,114°E~120°E)8d沙尘天气污染个例,在地基AERONET数据的数值约束下,利用CALIOP 数据和SBDART(Santa Barbara DISORT Atmospheric Radiative Transfer)辐射传输模式研究了华北地区沙尘天气气溶胶垂直分布特征,估算气溶胶直接辐射强迫廓线,探讨气溶胶垂直分布和光学特性对气溶胶直接辐射强迫的影响.1 研究数据及方法1.1研究数据主要用到的研究数据有AERONET气溶胶地基遥感观测网数据(),用来提供气溶胶光学和辐射特性信息;CALIOP卫星数据(https:///project/calipso/calipso_ table),用来提供气溶胶垂直分布信息.1.1.1 AERON ET地基观测站网 AERON ET利用CIMEL CE-318全自动太阳光度计测量340,380, 440,500,675,870,940,1020,1640nm通道的太阳直接和散射辐射,其中940nm通道用于观测水汽柱含量,其余通道用于观测气溶胶光学厚度(AOD)和Ångström指数(AE).此外,可反演得到440,675, 870,1020nm波段的复折射指数、单次散射反照率(SSA)、不对称因子(ASY)和短波辐射通量等参数[17-19].数据产品分为Level 2.0、Level 1.5、Level 1.0 共3个等级.研究过程中,Level 2.0数据质量最高, Level 1.5次之,Level 1.0不予使用.本文使用AERON ET Version 2 Inversions的Level 2.0数据,缺测时以Level 1.5数据补充,数据时间分辨率为15min.用到的华北地区站点有北京、北京-CAMS、北京_RADI、香河、徐州.使用到的具体参数是440,675,870nm波段的气溶胶光学厚度、单次散射反照率、不对称因子,440~870nm的Ångström指数,太阳天顶角和水汽柱含量,用于输入SBDART辐射传输模式计算气溶胶直接辐射强迫;大气层顶、地表向下和向上短波辐射通量,用于验证SBDART辐射传输模式模拟结果.站点详细信息见表1.表1华北地区AERONET站点信息Table 1 The information of AERONET sites in north China站点经纬度高程(m) 等级时间范围北京 (116.38°E,39.98°N)92 2.0 2013-01~2016-12北京-CAMS(116.32°E, 39.93°N)106 2.0 2013-01~2016-12北京_RADI(116.38°E, 40.00°N)59 1.5 2013-01~2016-12香河 (116.96°E,39.75°N)36 2.0 2013-01~2016-12徐州 (117.14°E,34.22°N)59 1.5 2013-07~2016-121.1.2 CALIOP卫星遥感数据 CALIOP搭载在2006年发射的CALIPSO卫星上,通过发射532nm和1064nm的激光脉冲,可以得到1064nm通道后向散射信号和532nm 2个正交偏振(平行和垂直)通道后向散射信号,从而提供全球高分辨率的气溶胶和云的垂直分布信息,包括后向散射系数、退偏比、色比和消光系数等光学参数[20-22].CALIOP每16 d可以获得一次全球气溶胶和云层的三维信息.本文使用CALIOP V4.10版本Level 2.0气溶胶廓线数据、Level 2.0气溶胶垂直特征数据(VFM)和Level 1.0数据.Level 2.0气溶胶廓线数据的水平分辨率是5km,垂直分辨率是60m(-0.5~8.2km高度范围),提供的参数有地表高程数据、532nm和1064nm 气溶胶消光系数、532nm和1064nm气溶胶后向散射系数和质量控制参数等.利用532nm气溶胶消光系数表示气溶胶垂直分布信息,对数据进行质量控制的方法和Winker等[23]类似,主要有:①无云;12期侯灿等：华北地区沙尘天气垂直气溶胶直接辐射强迫 5171②AVD =3;③CAD_Score 10002−≤≤−;④Ext_QC =0,1;⑤-1532nm 0Ext_Coef 1.25 km ≤≤;⑥0Ext_≤-1532nmCoef_Unc 99.9km ≤.其中,AVD =3表示是气溶胶;CAD_Score 用于评价云-气溶胶识别算法的可信度;Ext_QC 用于评价气溶胶消光系数的数据质量;532nm Ext_Coef 是532nm 气溶胶消光系数;532nm Ext_Coef_Unc 是532nm 气溶胶消光系数的不确定度.对数据进行质量控制后,垂直方向上进行五点平滑,以增加信噪比,并将垂直分辨率插值到0.3km.Level 2.0气溶胶垂直特征数据(VFM)和Level 1.0数据的水平分辨率为333m,垂直分辨率为30m (-0.5~8.2km 高度范围),利用Level 1.0数据的Total Attenuated Backscatter 532参数识别云、气溶胶和气体分子,进而利用Level 2.0气溶胶垂直特征数据(VFM)的Feature Classification Flags 参数识别气溶胶具体类型,分析气溶胶垂直分布特征. 1.2 区域划分和个例选择研究华北地区沙尘天气垂直气溶胶直接辐射强迫,需满足条件:(1)SBDART 辐射传输模式的关键输入参数存在观测数据;(2)440AOD 0.4≥,确保AERONET 反演单次散射反照率和复折射指数时误差小[18-19];(3)过境的CALIOP 气溶胶廓线数据在质量控制之后,0~8km 高度范围气溶胶垂直分布信息尽可能完整,减小估算垂直气溶胶直接辐射强迫的误差;(4)沙尘天气,即CALIOP 的VFM 数据识别出大量纯净沙尘型气溶胶或者污染沙尘型气溶胶.CALIOP 数据时间分辨率低,重返周期约16d,以表1中地基站点为中心选取半径为50 km 或者100km 圆域内卫星过境数据,卫星过境天数过少,无法选出同时满足上述4个条件的日期开展研究.为提高数据的利用率,将地基站点附近研究区域扩大,参考CALIOP L3全球数据是1.0×2.5 deg grid,华北地区有AERONET 站点的格点区域为(39°N~40°N, 115°E~117.5°E)和(34°N~35°N,115°E~117.5°E).北京、北京-CAMS 、北京_RADI 、香河4个站点位于(39°N~40°N,115°E~117.5°E)区域内,徐州站点位于(34°N~35°N,115°E~117.5°E)区域内.针对(39°N~40°N,115°E~117.5°E)和(34°N~ 35°N,115°E~117.5°E),CALIOP 卫星过境数据分别有17,19d,去除OMI 、MODIS 、AERONET 数据缺测和440AOD 0.4<的情况,分别有10,15d 可选择.CALIOP 数据质量控制之后会剔除部分数据,从这10,15d 中选择质量控制之后0~8km 高度范围CALIOP 数据完整且是沙尘天气的日期开展研究.满足条件的日期是2013年3月17日、2013年10月27日、2014年4月14日、2015年3月7日(39°N ~40°N,115°E~117.5°E);2014年4月7日、2015年4月10日、2016年4月12日、2016年5月5日(34°N ~35°N,115°E~117.5°E).为研究华北地区沙尘天气垂直气溶胶直接辐射强迫的共性,这8d 沙尘天气均保留.这8d 卫星过境时间均为夜间且1d 只有1条卫星过境数据.气溶胶垂直分布白天和夜间存在差异,但由于CALIOP 数据量过少,忽略气溶胶垂直分布的日际变化,以1.0×2.5 deg grid 区域内卫星过境数据作为当天气溶胶垂直分布信息. 1.3 研究方法1.3.1 气溶胶直接辐射强迫和直接辐射强迫效率计算方法气溶胶直接辐射强迫是指晴空条件下有无气溶胶的净辐射通量的差值.给定高度Z 、大气层顶(TOA)、地表(SFC)的气溶胶直接辐射强迫(ADRF)计算公式为[13,24]: aer noaerADRF =NF NF Z Z Z − (1) aer noaer TOA TOA TOA ADRF =NF NF − (2)aer noaerSFC SFC SFC ADRF =NF NF − (3)down up NF =F F − (4)式中:F down 和F up 分别是向下和向上辐射通量.辐射通量是指单位时间内通过任意表面的辐射能量[25].在大气辐射传输过程中,以向下为正方向,向上为负方向.以大气层顶为例,向下辐射通量表示进入地气系统的辐射能量,向上辐射能量表示反射回外太空的辐射能量;aer NF 和noaer NF 分别是有气溶胶和无气溶胶时的净辐射通量;ADRF 是气溶胶直接辐射强迫.大气层的气溶胶直接辐射强迫是大气层顶(TOA ADRF )和地表气溶胶直接辐射强迫(SFC ADRF )的差值[26-27],即ATM TOA SFC ADRF =ADRF ADRF − (5) 气溶胶直接辐射强迫效率定义为单位气溶胶光学厚度的气溶胶直接辐射强迫,即550ADRF/AOD ,去除了气溶胶直接辐射强迫对气溶胶光学厚度的依赖性,便于分析气溶胶光学特性对气溶胶直接辐射强迫的影响.由于AERONET 数据没有550nm 气溶胶光学厚度,利用440,870nm 气溶胶光学厚度和5172 中国环境科学 40卷440~870nm 的Ångström 指数插值得到550nm 气溶胶光学厚度,插值方法为[28]1232AE23AOD AOD (/)λλλλλλ−=× (6)1212-12AE (ln(AOD /AOD ))/ln(/)λλλλλλ=− (7) 式中:1λ,2λ,3λ分别为440,870,550nm.1.3.2 SBDART 辐射传输模式模拟 SBDART 辐射传输模式是一个用于计算晴空和有云条件下地球大气和地表的平面平行大气辐射传输的程序包[29].本文使用版本2.4进行模拟计算,该版本采用离散纵坐标法,LOWTRAN -7或者MODTRAN -3以及米散射计算大气辐射传输,提供了高达6组大气廓线,40个辐射传输流,65个大气层,波长范围覆盖红外、可见光和紫外波段,计算结果和地基观测数据吻合较好,相对误差小于3%[30-31].本文利用SBDART 辐射传输模式计算晴空条件下0.25~4.0um 短波波段的从大气层顶到地表的有无气溶胶的向下和向上辐射通量.有气溶胶时,运行SBDART 辐射传输模式采用四流近似,45个大气层,垂直分辨率设为0.3km .模式的关键输入参数有:整层气溶胶光学特性(440,675,870nm 气溶胶光学厚度、单次散射反照率、不对称因子和440~870nm 的Ångström 指数),气溶胶垂直分布信息(532nm 气溶胶消光系数),水汽柱含量,太阳天顶角,臭氧柱含量,地表反照率.整层气溶胶光学特性、水汽柱含量和太阳天顶角数据均来自AERON ET Version 2 Inversions 数据集,可以用来控制整层估算误差.单次散射反照率、不对称因子利用440,675,870nm 处数值线性内插或者外插到整个短波波段,气溶胶光学厚度利用440,675,870nm 处数值对数内插到440~ 870nm 范围内,结合Ångström 指数外插到440~ 870nm 范围外波段.气溶胶垂直分布信息来自CALIOP Level 2.0气溶胶廓线数据.臭氧柱含量数据来自OMI 传感器的Daily L3 Global 0.25*0.25 deg grid 数据[32-33].地表反照率数据来自MODIS 的日均融合产品MCD43D51[34-35].整层气溶胶光学特性、水汽柱含量和太阳天顶角一天多组数据,8d 沙尘天气共有65组数据,以1.0×2.5deg grid 区域内各站点瞬时值输入SBDART 模式.气溶胶垂直分布信息、臭氧柱含量和地表反照率一天一组数据,以1.0×2.5 deg grid 区域内水平方向的平均值输入SBDART 模式.无气溶胶时,运行SBDART 辐射传输模式将气溶胶输入参数关闭,即无整层气溶胶光学特性和气溶胶垂直分布信息,其他输入参数保持不变.利用式(1)~式(5)计算得到高度Z 、大气层顶、地表、大气层的瞬时气溶胶直接辐射强迫,进而计算得到瞬时气溶胶直接辐射强迫效率和日均气溶胶直接辐射强迫.SBDART 模式给出的气溶胶垂直分布是假定气溶胶消光系数随高度指数下降,将上述模拟过程中气溶胶垂直分布信息改为SBDART 模式给出的气溶胶垂直分布,其它输入参数保持不变,计算得到高度Z 、大气层顶、地表、大气层的瞬时气溶胶直接辐射强迫,进而计算得到日均气溶胶直接辐射强迫.对比两种模拟结果,探讨气溶胶垂直分布对大气层顶、地表、大气层的气溶胶直接辐射强迫和气溶胶直接辐射强迫垂直分布特征的影响. 2 结果和讨论2.1 气溶胶垂直分布特征已有研究表明,532nm 总衰减后向散射系数为4.5×10-3~0.1km -1⋅sr -1的部分代表的是云,即图1中红色至白色区域;0.8×10-3~4.5×10-3km -1⋅sr -1的是气溶胶粒子,即绿色至橙色区域;0.1×10-3~0.8×10-3km -1⋅sr -1的是气体分子,即蓝色区域[36-38].由图1可以看出,CALIOP 过境的格点区域地表及以上3km 范围有明显的绿色至橙色区域,气溶胶粒子集中分布在该高度范围,4~5km 范围存在气溶胶粒子,但含量较少,5km 以上绿色至橙色区域已不明显,气溶胶粒子含量很少.计算CALIOP 过境的格点区域内卫星数据水平方向的平均值,以532nm 气溶胶消光系数廓线表示气溶胶垂直分布.图2可以看出,气溶胶消光系数垂直分布特征明显,并非SBDART 模式假定的气溶胶消光系数随高度指数衰减的特征.高值区在3km 以下,最大值能达到1.38km -1,近地层污染严重,3km 以上气溶胶消光系数数值小于0.2km -1.2013年3月17日和2016年4月12日气溶胶消光系数垂直方向上为双峰型结构,峰值分别为(0.6km,0.86km -1)、(3.9km,0.18km -1)和(0.6km,0.51km -1)、(3.0km,0.32km -1).2013年10月27日、2014年4月7日和2015年4月10日3.5km 以下气溶胶消光系数随高度增加而减小,3.5km 以上气溶胶消光系数趋近于12期侯灿等：华北地区沙尘天气垂直气溶胶直接辐射强迫 51730.2015年3月7日气溶胶消光系数垂直方向上为单峰型结构,峰值为(1.2km,0.54km -1).2014年4月14日和2016年5月5日气溶胶消光系数垂直方向上波动性变化.图1 CALIOP 532nm 总衰减后向散射系数垂直剖面(km -1⋅sr -1)Fig.1 CALIOP altitude -orbit cross -section of total 532nm attenuated backscattering ( km -1⋅sr -1)左右列白色直线划定范围分别表示CALIOP 过境的格点区域(39°N~40°N,115°E~117.5°E)和(34°N~35°N,115°E ~117.5°E);红色实线表示地表高度;(a)2013-03-17,(c)2013-10-27,(e)2014-04-14,(g)2015-03-07;(b)2014-04-07,(d)2015-04-10,(f)2016-04-12,(h)2016-05-05图2 CALIOP 532nm 气溶胶消光系数区域平均廓线Fig.2 CALIOP area averaged prifiles of 532nm aerosol extinction coefficient(a)(39°N~40°N,115°E~117.5°E),(b)(34°N~35°N,115°E ~117.5°E)5174 中国环境科学 40卷由图3可见,这8d 以纯净沙尘型气溶胶和污染沙尘型气溶胶为主,污染大陆型气溶胶和烟雾为辅.纯净沙尘型气溶胶和污染沙尘型气溶胶位于上层,低层为污染大陆型气溶胶和烟雾,且污染大陆型气溶胶集中在0~1km 范围,烟雾高度相对较高,这一结论与Tao 等[39-40]给出的华北地区灰霾天气气溶胶分层结论类似.图3 CALIOP 气溶胶垂直特征掩模数据垂直剖面Fig.3 CALIOP altitu de -orbit cross -section of aerosol vertical feature mask data左右列白色直线划定范围分别表示CALIOP 过境的格点区域(39°N~40°N,115°E~117.5°E)和(34°N~35°N,115°E~117.5°E);(a)2013-03-17,(c)2013-10-27,(e)2014-04-14,(g)2015-03-07;(b)2014-04-07,(d)2015-04-10,(f)2016-04-12,(h)2016-05-052.2 气溶胶直接辐射强迫和垂直分布影响 2.2.1 结果验证与误差分析利用SBDART 模式计算晴空条件下有气溶胶时0.25~4.0um 短波波段大气层顶和地表瞬时向下、向上辐射通量,与AERONET 反演结果进行对比(图4).大气层顶向下辐射通量的回归参数R 2为0.998,平均误差为-3.41W/m 2,平均相对误差是0.98%,地表向下辐射通量的回归参数是0.998,平均误差为-6.86W/m 2,平均相对误差为2.13%.向下辐射通量的模式模拟结果和AERONET 的反演结果可以很好的吻合. AERONET 的反演算法中,大气辐射传输模式也是离散纵坐标法[18],而且SBDART 模式模拟和AERONET 反演辐射通量时的输入参数气溶胶光学特性、水汽柱含量和太阳天顶角的数据均来自AERONET,输入数据相同,因此向下辐射通量的验证精度很高.大气层顶向上辐射通量的回归参数为0.972,平均误差为-4.78W/m 2,平均相对误差为2.89%,地表向上辐射通量的回归参数为0.861,平均误差为-7.12W/m 2,平均相对误差为13.73%.向上辐射通量的模式模拟结果和AERONET 的反演结果也可以很好的吻合,但相比向下辐射通量的验证结果,向上辐射通量的拟合效果相对较弱.这是因为SBDART 模式模拟时的地表反照率数据来自MODIS,而AERONET 反演时的地表反照率数据是经过多次检验的气候均值.地表反照率在大气辐射传输过程中对向上辐射通量的影响大于对向下辐射通量的影响,而且对地表的影响最强.整体来说,利用SBDART 模式模拟的结果精度高,向下辐射通量的平均相对误差不超过3%,向上辐射通量的平均相对误差不超过14%.12期侯灿等：华北地区沙尘天气垂直气溶胶直接辐射强迫 5175图4 SBDART 模式模拟和AERONET 反演辐射通量对比结果Fig.4 Comparisons between the SBDART simulated and AERONET inversion products of SW fluxes(a)大气层顶向下辐射通量,(b)地表向下辐射通量,(c)大气层顶向上辐射通量,(d)地表向上辐射通量2.2.2 日均气溶胶直接辐射强迫和垂直分布影响由图5可以看出,日均550nm 气溶胶光学厚度为0.66~2.17,输入CALIOP 气溶胶廓线模拟得到的大气层顶、地表和大气层的日均气溶胶直接辐射强迫分别为-38.41~-88.44,-74.03~-225.86,9.06~ 137.42W/ m 2.大气层顶和地表的日均气溶胶直接辐射强迫为负值,大气层的日均气溶胶直接辐射强迫为正值,说明气溶胶在地气系统和地表产生冷却效应,在大气层产生增温效应.气溶胶吸收和散射入射的短波太阳光,使得入射太阳光部分能量留在地球大气中,到达地表的能量被衰减,从而气溶胶在大气层产生增温效应,在地表产生冷却效应.大气层增温,地表降温,会影响大气温度层结,有利于逆温层的产生,从而可能导致局地大气环流发生变化[41].由表2可知,本文模拟的气溶胶直接辐射强迫绝对值偏高.气溶胶直接辐射强迫绝对值随着光学厚度的增大而增大,考虑到本文的气溶胶光学厚度数值偏高,结合短波辐射通量的验证效果好,认为本文模拟的大气层顶、地表和大气层的气溶胶直接辐射强迫结果合理.Yu 等[42]的研究结果和本文接近,两者均模拟的是华北地区春季沙尘个例,气溶胶来源和组分接近,而其他研究结果和本文存在一定的差异,尤其是西北地区大气层顶气溶胶直接辐射强迫出现正值,这是因为大气层顶气溶胶辐射强迫对气溶胶吸收特性最为敏感,西北地区研究时段的气溶胶粒子吸收性较强.0.511.522.532013-03-172013-10-272014-04-142015-03-072014-04-072015-04-102016-04-122016-05-05日期550n m 气溶胶光学厚度5176中国环境科学 40卷-120-90-60-3002013-03-172013-10-272014-04-142015-03-072014-04-072015-04-102016-04-122016-05-05日期日均气溶胶直接辐射强迫(W /m 2)-300-250-200-150-100-5002013-03-172013-10-272014-04-142015-03-072014-04-072015-04-102016-04-122016-05-05日期日均气溶胶直接辐射强迫(W /m 2)501001502002013-03-172013-10-272014-04-142015-03-072014-04-072015-04-102016-04-122016-05-05日期日均气溶胶直接辐射强迫(W /m 2)图5 日均550nm 气溶胶光学厚度和大气层顶、地表、大气层的气溶胶直接辐射强迫Fig.5 Daily average values of aerosol optical depth at 550 nm, aerosol direct radiative forcing at TOA, at the surface, and in theatmosphere黑色斜线为输入CALIOP 观测的气溶胶廓线的模拟结果,黑色网格为输入SBDART 模式的气溶胶廓线的模拟结果表2 中国地区气溶胶光学厚度和大气层顶、地表、大气层的气溶胶直接辐射强迫(W/m 2)Table 2 Aerosol optical depth, aerosol direct radiative forcing at TOA, at the surface, and in the atmosphere (W/m 2) in China站点区域类型时间 AOD ADRF(T OA) ADRF(SFC) ADRF(A T M) 参考文献-塔克拉玛干沙漠沙尘气溶胶 2006-07-26~310.4~0.9 (532nm) 14.11 -64.72 78.83 [43] 太湖长江三角洲沙尘和沙尘、人为污染混合气溶胶2009-03-14~17和 2009-04-25~260.61±0.21和0.79±0.23(440nm) -13.6 和-21.4 -36.8 和-48.223.2 和26.8[44]敦煌西北沙尘气溶胶 2001-04~05 0.05~1.38 (500nm)-1.96~-63.26-4~-163.35 1.45~122.99 [27]民勤和SACOL 西北沙尘气溶胶 2010-04-24~300.20~0.65 5.93~35.7 -6.3~-30.94 16.77~56.32 [45]SACOL西北局地沙尘和人为污染混合气溶胶 2012-09-03、04、21、280.270~0.423(440nm)-12.71-25.40 12.69 [46]12期侯灿等：华北地区沙尘天气垂直气溶胶直接辐射强迫 5177续表2站点区域类型时间 AOD ADRF(T OA) ADRF(SFC) ADRF(A T M) 参考文献敦煌西北沙尘气溶胶 2012-04-01~06-12 0.28±0.21 (500nm) -25.2~11.9 -3.2~-79.4 2.2~25.1 [47] SACOL 西北沙尘气溶胶(沙尘暴) 2007-03-28 全天最大值2.15(440nm) 39.04-146.54 185.58 [48]北京华北沙尘气溶胶 2001-2014年春季沙尘个例1.42~2.32 (440nm) -65.88~-115.65-166.66~-236.02 86.72~133.67 [42] 北京、香河、徐州华北沙尘和沙尘、人为污染混合气溶胶#0.66~2.17 (550nm)-38.41~-88.44-74.03~-225.86 9.06~137.42本文注:#具体时间为2013-03-17、2013-10-27、2014-04-14、2015-03-07(39~40°N,115~117.5°E)和2014-04-07、2015-04-10、2016-04-12、2016-05-05 (34~35°N,115~117.5°E)由表3可见,大气层顶、地表、大气层的日均气溶胶直接辐射强迫的两种模拟结果数值接近,相对误差绝对值基本在3%以内,气溶胶垂直分布对大气层顶、地表、大气层的气溶胶直接辐射强迫影响很小.以往研究有类似结论,但同时指出强吸收性气溶胶粒子垂直分布对大气层顶气溶胶直接辐射强迫影响明显[8,11].本文沙尘天气多为纯净沙尘型、污染沙尘型、污染大陆型气溶胶和烟雾的混合物,440nm 单次散射反照率大于0.8,气溶胶吸收性弱,气溶胶垂直分布对大气层顶气溶胶直接辐射强迫影响小.表3 日均气溶胶直接辐射强迫误差(W/m 2)和相对误差(%) Table 3 The error (W/m 2) and relative error (%) of dailyaverage values of aerosol direct radiative forcing日期误差(大气层顶) 误差 (地表) 误差(大气层)相对误差 (大气层顶) 相对误差(地表)相对误差(大气层)2013-03-17 1.41 0.20 1.21 -1.59 -0.090.88 2013-10-27 0.29 0.06 0.23 -0.53 -0.030.19 2014-04-14 1.33 0.10 1.23 -1.57 -0.05 1.21 2015-03-07 0.54 0.09 0.45 -1.01 -0.080.69 2014-04-07 0.80 0.06 0.74 -1.76 -0.05 1.08 2015-04-10 -0.49 -0.09 -0.40 1.28 0.10-0.752016-04-12 1.42 -0.13 1.55 -2.15 0.1717.11 2016-05-05 -0.30 0.04 -0.34 0.68 -0.05-1.13由图6可见,日均气溶胶直接辐射强迫为负值,整体趋势是随着高度的增加绝对值逐渐减小.在大气辐射传输过程中,向下辐射通量和向上辐射通量均是从大气层顶到地表逐渐减小.气溶胶的吸收散射作用使得向下辐射通量的衰减增强,减小向下辐射通量,且大多情况气溶胶使得向上辐射通量增大,从而使得同一高度层净辐射通量减小,因此从大气层顶到地表的气溶胶直接辐射强迫基本是负值.同时,气溶胶对向下辐射通量的影响一般大于对向上辐射通量的影响,从大气层顶到地表,向下辐射通量的累积衰减作用逐渐增强,气溶胶直接辐射强迫的绝对值从大气层顶到地表逐渐增大.对比输入2种气溶胶廓线的0~8km 日均气溶胶直接辐射强迫廓线,气溶胶垂直分布对直接辐射强迫垂直分布特征影响明显.同一高度日均气溶胶直接辐射强迫最大差值能达到31.18W/m 2,最小差值能达到-18.86W/m 2.相比较输入CALIOP 观测的气溶胶廓线的模拟结果,输入SBDART 模式的气溶胶廓线模拟的直接辐射强迫垂直方向上平滑,这是因为SBDART 气溶胶廓线的气溶胶消光系数从地表到大气层顶随着高度增加指数衰减,也进一步说明了气溶胶垂直分布对直接辐射强迫垂直分布特征的影响.2468-250-200-150-100日均气溶胶直接辐射强迫(W/m 2)高度(k m )02468-120-100-80-60日均气溶胶直接辐射强迫(W/m 2)高度(k m )。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

a rXiv:as tr o-ph/51288v114Jan25VLF observation during Leonid Meteor Shower-2002from Kolkata Sandip K.Chakrabarti 1,2,S.Pal 2,K.Acharya 2,S.Mandal 2,S.Chakrabarti 2,3,R.Khan 2,4,B.Bose 2February 2,20081.S.N.Bose National Centre for Basic Sciences,JD-Block,Salt Lake,Kolkata 7000982.Centre for Space Physics,P-61Southend Gardens,Kolkata,7000843.Maharaja Manindra Chandra College,1Ramkanta Bose St.,Kolkata,7000024.Bidhan Nagar High School,BD block,Salt Lake,Kolkata,700064Abstract Using a Gyrator-II Loop antenna tuned at 19.0Khz,we monitored the meteor shower during 17-24th November,2002.We observe the primary peak at 3h58m (UT)on the 19th of November,2002.We distinctly observed several ‘beadlike’and ‘exponentially dropping’signals.The ‘beadlike’signals were more in abundance on the 18th of Novem-ber,2002,one day prior to the actual encounter.PUBLISHED IN INDIAN JOURNAL OF PHYSICS,2002,76B,6931Introduction Very Low Frequency (VLF)project of CSP has been monitoring VLF activities for quite some time and has detected solar ﬂares as well.During the recent Leonid shower event the CSP antenna was tuned to 19KHz and continuous observations were made for seven days.In this Rapid Communication we present the ﬁrst report of this observation.Leonid meteor showers are observed around 16-19th November for 3-4successive years after the perihelion passage of the periodic comet Temple-Tuttle (T ∼33Yrs).On February 28,1998,the comet reached its perihelion and in 1998-2002the visual observations indicated very good meteor showers.When the earth’s orbit crosses the debris left over by the comet on its path in its previous passages,a shower or storm may form,depending on the intensity of events.In 2002,several calculations indicated that there would be two peaks,one would be from Europe at around 4.00UT (due to earth’s passage through the dust trail left behind in 1767A.D.)and the other would be seen from North America at around 10.40UT (due to earth’s passage through the dust trail left behind in 1866A.D.)[2].Apart from encountering a rare celestial event,scientists are interested in Leonids because of the prospect of detecting bio-molecules which are thought to have contaminated the earth after being produced in space [3-5].Furthermore,it has been reported that electrophonic sounds have been recorded during Leonid showers [6-7]which are thought to be due to the fact that Very Low Frequency (VLF)electromagnatic (EM)waves are produced during the passage of a ﬁre-ball.Keay [8]and later Bronshten [9]suggested that these VLFs could be produceddue to entangling of earth’s magneticﬁeld in the tail of the bow-shock generated by an incoming meteor.More recently,it is thought that the VLFs are produced when aﬁreball bursts.In any case,the EM radiation emitted is found to have frequency ranging from a few Hz to about30KHz[8].This range is divided into three parts(a)Ultra-Low-Frequency (ULF,ν<300Hz),(b)Extreme Low Frequency(ELF,0.3<ν<3KHz)and(c)Very Low Frequency(VLF,3<ν<30KHz).In Centre for Space Physics,a team of scientists are engaged in monitoring solar ac-tivities continuously using two VLF detectors,one located near Kolkata and the other is located at Malda.Reports on these would be made elsewhere.Presently,we consider only the results of the monitoring of2002Leonid meteor shower.2Experimental SetupThe loop Antenna is made of a square frame of one meter on each side and several turns of shielded single core wire is used to receive the signal.The signal is then ampliﬁed and is fed into the audio card of a Pentium-IV computer located inside the laboratory. The audio signal is sampled at3.2times per second.The antenna is tuned at19KHz, away from the nearest18.2KHz signal transmitted by VTX3,Indian Navy traﬃc station at Vijayananarayanam.It is aligned along the East-West direction.The magneticﬁeld of the VLF signal induces a current in the antenna.The antenna near Kolkata was placed at a height of about12meters from the ground.The gain of the receiver is adjusted to obtain a decibel level of around1500when there is no signal.3ResultsFigs.1(a-c)show results of the output from2.15am to12.15am(-3h15m to6h45m UT)on (a)18th,(b)19th and(c)20th of November,2002.The dates on each curve are marked.The otherwise steady result is perturbed due to passages of meteors,and possible atmospheric phenomena such as thunderbolts[6,11-12].However,the days had very clear skies and no serious‘thunder-bolt’related events were expected.On the19th of November,at3h58m UT (9h28m IST),there was a distinct peak comprising of about70sub-structures,presumably from individual strong events.(Expected visual rate[Zenithal hourly rate or ZHR]Kolkata area was around100per hour at this time,while the visual observation of the CSP team from Bolpur was25per hour in between-1h30m to-0h30m UT).On the20th November there was some enhanced activity at around4h27m UT(9h57m IST)but not as much as on the19th.It is to be noted that the visual peak was observed by Leonid-MAC team at 4.09UT[3]very close to the peak found in VLF although several reports[10]indicated that the peak lies between3h48m to4h04m UT thereby bracketing our observation.In Fig.2,we present the results during the peak from3h30m UT to4h30m UT.The duration of the shower seems to be from3h38m to4h28m,i.e.the shower lasted for about50 minutes.This is similar to what is reported by Leonid-MAC and IMO.Each sub-structure in the peak is similar to an exponential decay curve,but the enhancement of the base(see Fig.1b and Fig.2)indicated that new signals were injected even before the earlier one has time to decay completely.The signal is easily modeled byΣi a0(i)exp(t/t0)over the injected We also observed two secondary peaks at around5h UT and5h45m UT.Some disturbances have been observed but no distinct peak was found at around10h50UT when the American peak was supposed to be formed.It is possible that the VLF signal at19KHz is washed out while traveling half-way across the globe.Throughout our observation there were mainly two types of signals.One is‘bead’-like and the other is exponentially decaying.In Fig.3a,we show one example of the‘bead-like’signal,typical of the proﬁle of multiple meteors.However unlike earlier observations[6-7, 12]where the signals lasted a few tenths of a second,our observed duration was much longer,several minutes.Also,earlier observers showed sharp spike like features at the beginning,while we miss it during the‘bead-formation’.It is possible that due to our low time resolution(∼300ms),multiple events merged together and long lasting beads were formed.In Fig.3b,we demonstrated a typical signal dropping exponentially.4Concluding RemarksThe VLF project of CSP has been able to observe the peak very distinctly at about3h58m UT on the19th of November,2002.We made the observation at a frequency far away from previously reported observations during1998and1999showers and conﬁrm that the meteors do emit VLF signals even at19KHz during their entry in earth’s atmosphere.What could be the cause of the VLF emission and what is the range in which it is emitted?We believe that the bow-shock that is formed in-front of the highly supersonic meteor becomes unstable due to Kelvin-Helmholtz(K-H)instability along with the tan-gential discontinuity which separates the evaporated matter from the meteor head and the shock-compressed matter in between the bow-shock and the tangential discontinuity.If one considers the bow-shock alone,a strong shock will compress theﬂow by a factor ofρ1/ρ2∼4 [13]and the tangential velocity diﬀerence would be v1−v2∼0−30km depending on the location of the bow-shock,highest being at an angleθ∼30−45o with the propagation axis and the lowest being at the stagnation point(θ∼0)and downstream farther away (θ∼180o),where the bow-shock loses its identity.The frequencyνof the K-H instabilityis given by[13],ν2KH=1(ρ1+ρ2)2(v1−v2)2.Assuming,ρ1/ρ2∼1/4,weﬁnd that anywhere between0to180KHz could be produced with very small amplitude on both the ends(at the stagnation point of the bow-shock and farther out).It is possible that the earth’s magneticﬁeld entangled in the vortices at this K-H unstable interface generate E-M waves of the same frequency.References[1]S K Chakrabarti,K Acharya,B Bose and R Khan,2002(submitted)[2]/leonids[3]/[4]S Chakrabarti and S K Chakrabarti2000,Astron.Astrophys.Lett.,354,L6[5]S K Chakrabarti and S Chakrabarti,2000,Ind.J.Phys.74B,97[6]C Price and M Blum,2000,Earth,Moon,and Planets,82,545[7]S Garaz,et al.,1999,Fizika A8,91[8]C S L Keay,1980,210,11[9]V A Bronshten,1983,Solar System Res.,17,70[10]/[11]C S L Keay,1995,Earth,Moon,and Planets68,361[12]M Beech,P Brown and J Jones,1995,Earth,Moon and Planets68,181[13]L D Landau and E M Lifshitz,Fluid Mechanics1962,(Pargamon:New York)Figure CaptionsFig.1(a-c):VLF signal variation during2h15m and12h15m IST(-3h15m UT to6h45m UT)during18th-20th November,2002.The peak occurs at3h58m UT on the19th.Some ‘beadlike’and‘exponentially decaying’signals could also be found.Fig.2:Details of the signal during the peak hour of the Leonid shower on the19th of Nov. 2002.The peak is made up of at least70distinct events and is observed at3h58m UT hour with a duration of about50minutes.There were secondary peaks at5h UT and5h45m UT.Fig.3(a-b):(a)Details of a‘beadlike’signal lasting for about three minutes.It is possible that it is made up of superposition of smaller events.(b)Details of an‘exponentially decaying’event.The recovery time scale is about100s.。