Wind profile warning characteristics of short-term heavy rain during the Meiyu season

This study examines the spatial and temporal distributions of short-term heavy rain (SHR) in the middle Yangtze River basin (MYRB) in the summers of the past decade. SHR events are most frequent during the annual Meiyu periods, significantly contributing to total precipitation. Additionally, these events generally last longer and tend to peak at night. The occurrence of SHR events decrease from southeast to northwest, influenced by the monsoonal flow and the small-scale terrain. Moisture convergence prior to Meiyu SHR events is predominantly influenced by both southerly and easterly winds below 700 hPa. Frequent low-level jets and quasi-steady cyclonic circulation lead to strong southerly winds prevailing over the eastern MYRB, while weaker easterly winds dominate in the west. Wind profiles derived from wind profile radar products illustrate the preceding changes in wind speed, wind directions, and vertical wind shear below 4 km above ground level (AGL), as well as the timing of these changes. In the plain area of southeastern MYRB, accelerated southwesterlies are observed 3 to 4 hours before SHR events, accompanied by an intensification of southerly winds near the boundary layer top 2 hours prior. Within the hour leading up to the SHR events, wind speeds sharply rise to their peak. In front of the mountains in west MYRB, southwesterlies strengthen 5 hours in advance but then weaken as they shift to northerlies. Just before the SHR events, however, reinforced northerlies occur near the surface. In the mountainous region of western MYRB, while changes in wind speed are minimal due to topographic blocking, the frequency of southeasterly components below 2 km AGL significantly increases 4 hours before SHR events. The preceding timing of significant vertical wind shear coincides with the increase in wind speed and the change in wind direction. Understanding the detailed characteristics of wind profiles preceding the SHR events during the Meiyu seasons can provide valuable insights for localized severe weather early warning systems.