Characteristics of cold air events with different intensities and cooling effects on winter temperature in China
Based on the National Centers for Environmental Prediction/National Center for Atmospheric Research reanalysis data from 1979 to 2019,the cold air outbreak index and two-dimensional blocking high index were used to screen out three types of cold air events with different intensities,i.e.high-to-middle latitudes(H-M),high-to-low latitudes(H-L),middle-to-low latitudes(M-L)events and Ural blocking high(UBH)events.The evolution characteristics of the three cold air events in winter,and the basic characteristics of the three cold events under the background of UBH and their cooling effect on China were analyzed,with the results that the frequency of H-M and M-L events showed a downward trend before 2000,and the intensity of M-L events generally showed a decreasing trend.Under the influ-ence of the blocking highs,66.1％of the cold air events were strong(cold air outbreaks index ≥2),the du-ration of 46.4％cold air events being 1 day,and the average duration of H-L events the longest(3.4 days).The cold airmass flux of the three types of events over the Eurasian continent at high latitudes showed a dipole distribution composed of the Siberian anticyclone and the North East Asian cyclone.Under the influence of the blocking highs,the northerly wind was strengthened,and the amount of cold airmass anomaly at the south entrance of cold air could reach more than 110 hPa before and after the onset days of the events,the negative temperature anomaly at 50°N was also affected more deeply,which could be extended above 500 hPa.The strong negative heat content anomaly corresponded to the strong tem-perature anomaly.On the onset day of a cold event,the negative heat content anomaly at 50°N was much larger than that at 30°N.When the three types of events occurred,the cooling regions were mainly con-centrated in the northern and eastern regions of China,with the cooling effect of H-L events being the strongest,for penetrating cold air events easy to form from high latitudes to southern China.
cold waveblocking high pressurepenetrating cold airSiberian high
万方数据
维普
