四川省2023年主汛期强降水的云图释用

Interpretation of Satellite Images Showing Heavy Rainfall during the 2023 Main Flood Season in Sichuan Province

摘要: 全球变暖背景下极端强降水频发，四川主汛期暴雨易引发地质灾害。本文选取2023年7月四川境内三次典型持续性强降水过程作为研究个例，综合运用中国气象局地面自动气象站观测资料与日本葵花9号静止卫星多通道遥感数据，采用天气学诊断手段，系统对比分析三次暴雨过程的大尺度环流配置、中尺度对流云团演变规律以及红外、水汽通道云顶亮温演变特征。结果表明：① 四川主汛期强降水过程的发生发展与西太平洋副热带高压的位置、强度密切相关，多数过程伴随短波槽、气旋式切变系统，部分过程叠加台风外围环流；② 单次持续性降水过程由多轮对流活动接续演变构成，对流云团初生阶段持续时间短，短时强降水往往同步出现在对流初生时段；③ 红外与水汽通道最低亮温持续降低是对流快速发展的典型判据，在适宜环境条件下，通过跟踪两类通道亮温动态变化，可对强对流及短时强降水开展短时监测预警。本研究成果可为四川及西南地区暴雨短时预报、卫星云图本地化释用提供支撑。

Abstract: Against the backdrop of global warming, extreme heavy rainfall has become increasingly frequent, and torrential downpours during Sichuan’s main flood season are prone to triggering geological disasters. This paper selects three typical episodes of persistent heavy rainfall in Sichuan in July 2023 as case studies. By comprehensively utilising observational data from the China Meteorological Administration’s ground-based automatic weather stations and multi-channel remote sensing data from Japan’s Aoi-9 geostationary satellite, and employing meteorological diagnostic methods, to systematically compare and analyse the large-scale circulation patterns, mesoscale convective cloud cluster evolution, and the evolution of cloud-top brightness temperatures in the infrared and water vapour channels during these three torrential rain events. The results indicate that: ① The occurrence and development of heavy precipitation events during Sichuan’s main flood season are closely related to the position and intensity of the Western Pacific Subtropical High; most events are accompanied by short-wave troughs and cyclonic shear systems, whilst some are superimposed by the peripheral circulation of typhoons; ② A single persistent precipitation event consists of successive rounds of convective activity; the initial stage of convective cloud clusters is short-lived, and short-duration heavy rainfall often occurs simultaneously during this initial phase; ③ A continuous decrease in the minimum brightness temperature in the infrared and water vapour channels is a typical indicator of rapid convective development; under suitable environmental conditions, short-term monitoring and early warning of severe convection and short-duration heavy rainfall can be carried out by tracking the dynamic changes in brightness temperature across these two channels. The findings of this study can provide support for short-term forecasting of torrential rain and the localised interpretation of satellite cloud imagery in Sichuan and the south-western region.