Satellite‐Derived 700‐hPa Geopotential Height Fields for Localization of Southwest Vortices and Diagnosis of Their Lower‐Tropospheric Environments

Abstract

Topographic gravity waves over the Tibetan Plateau generate downstream southwest vortices (SWVs) that are difficult to localize objectively and often produce heavy precipitation across mainland China. We introduce a new geopotential‐height‐only framework for SWV localization and characterization of their lower‐tropospheric environments using only satellite microwave temperature‐sounding observations from a three‐orbit polar satellite constellation—FY‐3E, MetOp‐C, and NOAA‐20. First, we demonstrate that localization accuracy comparable to conventional methods can be achieved by identifying the center of an ellipse fitted to the largest connected region of 700‐hPa geopotential height values below the first‐decile threshold, thereby eliminating the need for vorticity and wind information. We then apply this approach to geopotential height fields retrieved from these satellite microwave temperature‐sounding observations for 22 SWV cases occurring in 2023, enabling satellite‐based tracking and characterization of associated lower‐tropospheric environments, independently supported by Himawari‐9 infrared brightness temperatures. In addition, the satellite‐derived geopotential height fields are further evaluated against ERA5 reanalysis fields, ERA5 all‐sky brightness temperature simulation‐derived geopotential height fields, and a random‐forest‐based SWV tracking method, demonstrating overall consistency and robustness of the proposed framework. This capability enables observation‐driven localization and environmental diagnosis of mesoscale weather systems, particularly in regions with sparse conventional observations.