科研之友
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摘要
Based on daily precipitation data from 1980 to 2015 for 632 meteorological observational stations in China, 7 heavy rainfall events in Jianghuai region were selected. The spatial distribution and circulation pattern of these 7 heavy rainfall events in Jianghuai region were calculated using the Empirical Orthogonal EOF) expansion and synthesis. The leading mode of Empirical Orthogonal EOF) (can explain 22. 4% of the total variance) manifests when heavy rainfall event occurs in Jianghuai region, precipitations in northern part and in southern part of Jianghuai region show inverse relationship, the precipitation pattern shows “-+-” distribution from north to south over Eastern China. Precipitation anomalies of the second EOF mode (can explain 17. 8% of the total variance)shows that when heavy rainfall event occurs in Jianghuai region, precipitation in southeastern part and in central and western parts of Jianghuai region show inverse relationship, the precipitation pattern form north to south over eastern China is “-+”dipole distributions. The 500 hPa mean geopotential height field shows that, circulation feature shows Two-trough and One-ridge from Balkhash Lake to Northeast China in mid-latitude region. Using the principal components of the first EOF mode of the heavy rainfall events in Jianghuai region and the 500 hPa geopotential height field to get correlation coefficients. The result shows that, the contour distribution in the western part of Northeast China and the contour distribution in the eastern part of Inner Mongolia show in-verse correlation with the precipitation in Jianghuai region. 850 hPa’s wind blows northward over Jianghuai re-gion. In the correlation coefficients field, the v-direction wind field from the southern part of Northeast China to North China shows inverse correlation with the precipitation in Jianghuai region. The result shows that, when the trough in Balkhash Lake and the trough in Northeast China get stronger, north wind over North China assembles with south wind over Jianghuai region. Meanwhile, confluence of cold air and warm air leading to more precipi-tation over Jianghuai region. Precipitation pattern is of the first EOF mode.
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