冬季超大胞雷雨之诊断与模拟

120°E
As 850 hPa front was farther north of 925 hPa front by 100200 km, the surface-based postfrontal cold air over the area of storm development was rather shallow and confined to below 925 hPa in the morning of 19 December 2002.
2. Case Description
Fujian Lungyen Doppler Radar 0.5° base reflectivity from 1455 to 2259 LST (every 6 min):
(a) 1455 LST (f) 1727 LST (k) 1957 LST
(b) 1525 LST
3. Environmental Conditions
Surface analysis
0000 UTC (0800 LST) 19 Dec. 2002 1200 UTC (2000 LST) 19 Dec.
Northerly flow prevailed over much of the East Asia under the control of the Siberian high. A NE-SW-oriented cold front extended from the Japan area to southern Taiwan. The severe thunderstorms on 19 December developed around 1400 LST over southern Fujian / eastern Guangdong, behind the surface cold front in a post-frontal environment
(2) Purpose
To understand the synoptic and mesoscale environment that were favorable for the initiation and intensification of supercell thunderstorms. Using a cloud model, with real terrain, analysis data, and no initial thermal perturbation to simulate and diagnose storm structure, Kinematics, splitting process, and the variation in the mesoscale environment.
Shantou sounding at 0800 LST 19 Dec.
Favorable Environment :
The supercells occurred behind a winter cold front which provided a large west-southwesterly vertical wind shear of 6.4 × 10−3 s−1 at 0-3 km. Weak-to-moderate instability (CAPE = 887 J kg−1) above the shallow surface cold air.
陳 泰 然
學術副校長 / 臺大講座 / 大氣科學系終身特聘教授 國立臺灣大學
1. Motivation and Purpose 2. Case Description 3. Environmental Conditions 4. Mesoanalyses of Storm Environment 5. Model Description 6. Model Results
Low-level bulk shear = 6.4 × 10−3 s−1
Summary
The supercells occurred over the shallow cold air behind a winter cold front, with a large westsouthwesterly vertical wind shear of 6.4 × 10−3 s−1 at 0-3 km. This combined with weak-to-moderate instability (CAPE = 887 J kg−1) above the shallow surface cold air to yield a favorable environment for supercells.
700 hPa at 0000 UTC 19 Dec.
200 hPa at 0000 UTC 19 Dec.
Strong vertical shear (700 hPa LLJ near Fujian and Taiwan) associated with the cold front and instability. An approaching ULJ at 200 hPa also provided strong shear through deep layers, a factor beneficial to the longevity of supercell storms .
1. Motivation and Purpose
(1) Motivation
Three storms formed over Fujian / Guangding, intensified into isolated supercells, splitted and propagated eastward across the Taiwan Strait, made landfall over Taiwan and produced rain, hail, and property damage in Dec. 19,2002. Supercell thunderstorms are rare in the subtropics, not reported in open literature south of 25oN over Southeat Asia / western North Pacific. Northern storm registered a reflectivity of 72 dBZ, the strongest ever observed by any radar in Taiwan. A cargo plane crashed with the loss of two pilots near Penghu Islands late on 19 December as it encountered a hailstorm. 15 min of hail up to 2 cm in diameter, caused power outage and agriculture damage U.S. $ 6 M.
4. Mesoanalyses of Storm Environment
GMS-5 IR cloud imagery
(a) 0800 LST 19 Dec. 2002
30N
Manual mesoscale surface analyses
(c) 1400 LST, 19 Dec
(a) 0800 LST, 19 Dec (a)
The storms on 19 December evolved into three isolated supercells, which exhibited storm splitting and propagated eastward for 550 km to make landfall over Taiwan.
Reflectivity contours from Lungyen and CWB radars (30, 40, 50 dBZ) during 1455-2300 LST
After formation, the three storms evolved into isolated supercells and each experienced multiple splits. The right-movers were usually stronger than leftmovers and traveled eastward rapidly at about 18 m s−1 across the Taiwan Strait.
(c) 1556 LST
(h) 1826 LST
(m) 2057 LST
(d) 1626 LST
(i) 1856 LST
(n) 2158 LST
(e) 1656 LST 530 km
(j) 1926 LST 530 km
(o) 2259 LST 530 km
Three primary storms and their tracks:
925 hPa at 0000 UTC 19 Dec.
(a)
850 hPa at 0000 UTC 19 Dec.
(b)
30°N
30°N
20°N 925 hPa 0800 LST 19 Dec 2002
20°N 850 hPa 0800 LST 19 Dec 2002Βιβλιοθήκη 110°E120°E
110°E
(d) 1926 LST, C1
(f) 1832 LST, S1
Inflow notch Inflow notch Inflow notch Pendant echo Pendant echo
104 km
104 km
104 km