Statistical Characteristics and Circulation Patterns of Hails in Guangdong in Recent 10 Years
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Abstract:
The temporal and spatial distributions, circulation patterns and physical quantities of hails in Guangdong in Recent 10 years are analyzed. In Guangdong, hail weather occurs mostly in March, April and May, and hails occurred more frequently in the northern Guangdong and the Xijiang River region. The typical circulation patterns of hails can be divided into three types: cold front with trough (typeⅠ), warm zoon (typeⅡ), and elevated thunderstorms (type Ⅲ). Most severe hails happened in typeⅠ; that is，the cold front accompanies with the lowlevel shear line (vortex) and upper trough (temperature trough), and the surface cold air and the intrusion of temperature trough at upper levels make the atmosphere unstable. Severe convective weather is driven by the cold front, shear line, and trough, and the locations of hails in typeⅠare usually in front of the upperlevel trough, near the cold front and shear line. In typeⅡ, there is no cold front to the south of the Yangtze River on surface, and there is a convergence region of southeasterly and southerly at low levels over Guangdong. The drycold air brought by the upperlevel trough overlaps over the warmmoist air, leading to unstable stratification. The locations of hails in typeⅡare usually in the convergence region in front of the trough. In type Ⅲ, Guangdong is behind a cold front, and there is a lowlevel temperature inversion, and warm and moist air lifting convectively above the temperature inversion. The locations of hails in type Ⅲ are often near the shear line and hails are generally small.The mean environmental physical quantities favorable for severe hails are: the height of 0 ℃ is 4505 m; the height of －20 ℃ is 7632 m; Kindex is 35 ℃; SIindex is －099 ℃; the vertical wind shear is 267×10-3 s-1; the pressure vertical velocity is －28×10-2Pa/s; differential temperature advection between 400 hPa and 700 hPa is －239×10-5℃/s. Severe hails require larger Kindex, vertical wind shear, vertical velocity, differential temperature advection, more water vapor supply and smaller SIindex.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.