Southward Movement of the Decadal Drought in Southeastern China during April-May and Numerical Simulation of the Effect of the Condensation Heating
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Abstract
This study investigates the decadal change of East Asian climate from April to May, using the 10-day mean data of 560 meteorological stations in China and the ERA-40 reanalysis data during 1958-2000. Results show that the decadal drought in Southeastern China occurring in the late 1970s exists from mid-April to mid-May, moving southward with time. This southward moving feature is consistent with the decadal cooling in the middle and upper troposphere. Both of the anomalous subsidence and northerlies in the lower troposphere associated with the upper cooling occur from mid-April to mid-May and move southward. The southward movement of the decadal drought implies that April precipitation in the Huanghe River-Huaihe River basin is an indicator of the amplitude of southern China precipitation in May. The drought tends to occur in the south of the upper cooling region, which suggests that the decrease of the latent heating in the drought region may in turn cool the upper troposphere. This is verified in a sensitive experiment with a regional model. This partly explains the persistence and southward movement of the cooling signal in the atmosphere in late spring.
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