Abstract:

Using the conventional meteorological data,the FY-2G satellite data,and the National Centers for Environment Prediction (NCEP) reanalysis data with a horizontal resolution of 1°×1°,a rainstorm event caused by a cold vortex on June 6-7,2017 in Southeastern Inner Mongolia was investigated.The results showed that a westerly trough moves eastwards slowly and develops into a vortex under the stable synoptic conditions characterized by "one trough and one ridge" and in presence of a stable blocking high.Rainstorm occurs during the development period of the cold vortex.The Low-Level Jets (LLJs) transport abundant water vapor from the south and the water vapor budget primarily concentrates below 700 hPa.The net income of water vapor increases obviously before the rainstorm occurs,especially from the southern and northern boundaries.In addition,warm and moist southerly flows favor the formation of unstable atmospheric stratification and the energy accumulation in the rainstorm area.The coupled high-level jets and LLJs provide dynamic conditions for the occurrence of a rainstorm.The humidity field varies significantly before and after the rainstorm,with the maximum precipitable water vapor reaches 55-60 kg·m^-2.The precipitable water vapor increases significantly before the rainstorm,by nearly 2 times.The specific humidity over the rainstorm area at 700 hPa (850 hPa) is not less than 7 g·kg^-1 (12 g·kg^-1).Strong precipitation mainly occurs in areas where the maximum specific humidity and a temperature of the black body (TBB) <230 K occur,after the white bright zone breaks and disappears in the satellite water vapor images.

Key words: Blocking situation, Cold vortex, Rainstorm, Characteristics of water vapor