ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Archive > Volume 47 Issue 2 > 2021,47(2):242-252. DOI:10.7519/j.issn.1000-0526.2021.02.010 Prev Next
Cause Analysis of a Severe Downburst in Guilin
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Abstract:
An extreme gale event, hereinafter referred to as “3.21 Lingui gale event”, occurred in Lingui, Guangxi on 21 March 2019. Maximum gust of 60.3 m·s-1 (Grade 17) was recorded at the Lingui Station at 21:13 BT. Based on the results of the wind damage survey with video and meteorological data, this paper shows that the serious wind damage was caused by a severe microburst. Using the data from conventional meteorological observations, dense automatic weather station, radiosonde, Doppler weather radar, this paper analyzes the environmental conditions and influencing systems of the “3.21 Lingui gale event”. Results are that the “3.21 Lingui gale event” occurred under some favorable conditions such as active lowlevel warm and humid air flow, midlevel significant dry layer and strong lowlevel vertical wind shear. The event was triggered by the surface mesoscale convergence line and the southward cold front. The “3.21 Lingui gale event” was caused by the merging of two 〖JP2〗supercells into one supercell. Before the downburst occurred, the supercell developed to the most powerful stage. The maximum reflectivity core height (HGT) exceeded 6 km. There was a medium intensity of the mesocyclone accompanied by the (midaltitude radial convergence, MARC) value of 36 m·s-1. When the downbursts occurred, reflectivity factor began to weaken, the height of storm top dropped and HGT dropped. When HGT dropped sharply, the scanned volume interval dropped by 3.5 km, and the extreme gale of Grade 17 occurred. At this time, the lowlevel 0.5° elevation was observed in the highaltitude area of the cyclone, with a high radial divergence value of 27 m·s-1. The mesocyclone had the strongest wind shear strengthening, the bottom height rapidly dropped to less than 1 km, and so on. In addition, the occurrence of downburst was closely related to the dragging effect of extreme severe precipitation and hail. Usually, when the minutely rainfall is higher than 3 mm, wind force is higher than Grade 12; when the minutely rainfall is higher than 6 mm, the extreme gale of Grade 17 occurs.
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P445，P458
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