暴雨灾害 (Apr 2022)
Analysis of an early spring convective weather event in southwest of Hubei province based on multi-source data
Abstract
The meso-and micro-scale characteristics of an early spring convective weather event in southwest of Hubei on February 14, 2020 is analyzed comprehensively by using multi-source detection data such as Doppler weather radar, wind profile radar, micro rain radar, two-dimensional video disdrometer and three-dimensional lightning monitoring network, and then the application of the classified severe convective weather identification and warning algorithm is discussed. The results show that: (1) Because of the blocking effect of the mountains in southwest of Hubei, the cold front moves southward slowly in the north of Yichang, and an unstable stratification of upper dry and lower wet, induced by the intersection of the low trough of North China, the warm shear line in the north of the 850 hPa vortex and the cold air infiltrating in front of the cold front, forms in southwest of Hubei. Due to the combination of the warm and humid air of the mid- and low-level southwesterly flow transported along the lower frontal zone, the 850 hPa low level shear line, the surface cold front and the warm inverted trough, the convection is triggered and intensified, and the strong hail occurs at the intersection of the cold front and the warm inverted trough. (2) The wind profile radar data indicate that the southwest of Hubei is located in the warm inverted trough in front of the surface cold front. The continuous enhancement of the middle-upper level southwesterly jet and the incessant infiltration of cold air in front of the cold front jointly stimulate the occurrence and development of strong convection. (3) Disdrometer results illustrate that the raindrop pattern captured the accompanying precipitation process, with the particle diameter mostly within 1 mm and the maximum diameter close to 6 mm. (4) According to the characteristics of raindrop vertical distribution detected by the micro rain radar, due to the low environmental humidity in the early stage of precipitation, remarkable evaporation is existing; but in heavy precipitation period, the effect of coalescence and growth of raindrops near the ground is obvious. (5) The lightning frequency obtained by three-dimensional lightning monitoring network is positively correlated with the intensity variation of hailstorms, and the initial ground flash of two hailstorms is about 30 min and 33 min in advance of hailstone falling, respectively. (6) Doppler radar detected typical hail echo characteristics such as bounded weak echo area and hook-like echo, while the existence of mesocyclone, middle radial convergence and upper divergence area indicates that strong updraft is maintained in convective clouds, which is conducive to the generation and growth of hailstones.
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