Based on the observational data and ERA5 reanalysis data,the causes of the freezing rain disaster weath-er were studied by composite analysis methods from the perspective of circulation background at Harbin Taiping International Airport on November 8,2021.The results show that the temperature over Harbin Airport during the freezing rain has a significant"cold-warm-cold"characteristic,which is a typical"melting mechanism".The key factors of this process are the stable maintenance of 850 hPa low-level warm and humid southeast jet stream and low-level inversion layer,and the lower surface temperature of 2～4 ℃ under the risk control system of northeast surface.According to the Lagrange trajectory model(Hysplit),it is found that there are three main water vapor channels affecting the freezing rain weather of Harbin Airport.The second water vapor channel originating from the Sea of Okhotsk at the height of 850 hPa is the main water vapor channel during the precipitation process,and the Sea of Japan is the important water vapor source.The weather process occurred under the climate background of bimodal La Nina event,and the circulation field,surface pressure field and temperature field showed some abnor-mal characteristics compared with the same period in previous years.The bimodal La Nina years show the abnor-mal characteristics of strong warm and humid air flow and low surface temperature,which is similar to this process.
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