ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Statistical Study on the Radar Echo Characteristics of Downbursts under Weak Vertical Wind Shear in Jiangsu Province
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Abstract:
Abstract：To enhance the understanding of the structural characteristics of downburst storms under weak dynamic forcing (controlled by subtropical high with vertical wind shear below 10 m·s-1), and to evaluate the probability of operational weather radar in downburst warning. Based on the observation data of 12 SA-Doppler weather radars, this study statistically analyzes the storm structure characteristics of the downburst samples in Jiangsu Province from June to September during 2019–2020. The results indicate that under weak vertical wind shear, downburst storms exhibit relatively high reflectivity, with a mean reflectivity core of 57 dBZ and a height of 5.2 km above the ground. Approximately 1/3 of the storms are pulse storms. Downburst storms often accompanied by a descending reflectivity core (DRC) and decreasing vertical integrated liquid water content (VIL), with slow descent speed and a duration of 1-2 volume, and the lead time for warning is 0-12 min. Gust fronts are detected in 47% of downburst storms, and the average motion speeds of both storms and gust fronts are 7 m·s?1. The proportion of middle altitude radial convergence(MARC) and other radar signatures is not high. About 1/3 of the downburst storms are associated with MARC, while weak echo region (WER), rear inflow (RI), and mesovortices each occur in fewer than 10% of cases. However, downbursts associated with pulse storms, MARC, or other features tend to be more intense, and severe downbursts often reoccur after the initial downbursts. The duration of MARC and other features primarily ranges between 12-36 min. The warning lead times for downbursts and the severe downbursts by MARC and other features are 0-24 min and 6-36 min, respectively. The above quantitative structural characteristics advance the understanding of downburst storms, and indicate that operational weather radars can only provide warnings for part of downbursts, revealing limitations in downbursts warning under weak dynamic forcing.
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