Detection of Atmospheric Blocking and Northeast China Cold Vortex Using Satellite Microwave Temperature-Sounding Observations

The occurrence of atmospheric blocking signifies a remarkable transition from zonal to meridional circulation at 500 hPa. Its cutoff low may evolve into a northeast China cold vortex (NCCV), causing extreme weather, such as heavy rainfall and hailstorms. In this study, satellite-based microwave temperature-sounding data are used for tracking NCCV movements and for detecting blocking occurrences. The NCCV movement tracks are identified by the warm centers of brightness temperature measurements of the sounding channel, whose peak weighting function (WF) is located at 200 hPa. For the detection of blocking, a linear regression is first established between 500-hPa geopotential height and advanced microwave sounding unit-A (AMSU-A) channels 4–8; and the blocking index is then calculated for the identification of blocking. Here, the block index is calculated as the difference in 500-hPa geopotential height between 40°N and 60°N. Time-longitude plots of the blocking index, together with sequences of 500-hPa-height charts, for two blocking events that occurred in May 2023 and August 2020, compared well with those obtained by the ERA5 global reanalysis. The cutoff low of both blockings developed into NCCVs. This enables operational forecasters to directly and conveniently extract geopotential height information from satellite raw measurements of brightness temperature for weather diagnosis and forecasting. It also provides novel methodologies for analyzing of atmospheric large-scale circulation in recent decades, given more than 26 years of satellite-based microwave temperature-sounding data globally.