Impact Of Huai River Basin Soil Temperature And Humidity Abnormality In Pre-winter And Springtime On The Anomalous Summer Rainfall

With REOF analyze technique, the mainly anomalous spatial features of soil humidity in the 0-50cm layer of Huai River basin and their relations to different periods of precipitation and air temperature are specially analyzed by using the observed data including dekad averaged soil moisture, precipitation and air temperature data over the east of China from 1990 to 2000 .The results indicate that in the springtime the 30cm layer soil can be treated as a boundary. From Ocm layer to 30cm layer, the first rotated loading vector field in every layer reflects the anomalous soil humidity pattern in Huai River basin, we call the pattern structure as 'Huai River pattern' . While from 30cm layer to 50cm layer, the second rotated loading vector field in every layer is also quite similar to ' Huai River pattern' . In the summer and autumn the 'Huai River pattern' is still remarkable but the feature is less prominent than that in the springtime. We also find soil moisture anomaly of this pattern in every layer has notable duration and a prominent period of nearly forty dekads. Furthermore Positive (negative) correlation between soil moisture and precipitation (air temperature) during prophase and the same period can be found. And negative (positive) correlation between soil moisture and the precipitation (air temperature) of nearly half a year later can also be noted.Since the summer rainfall abnormality has closely relationship with both the soil moisture and temperature abnormality. We study the impact of pre-wintertime and springtime soil moisture and temperature on the summer rainfall over Huai river basin. In this paper, we present a blending method of dynamical and statistical approaches to choose theattributing factors that may effect the precipitation. The approaches establish a relationship between monthly precipitation abnormality and monthly circulation, soil moisture and temperature on the shallow and deep layers. The relationship is the precipitation diagnostic equation and its coefficients and dimensions are determined by using the observed data of Huai river basin. Then we select the main soil moisture and temperature attributing factors by the dimensional analysis to establish a forecasting equation of summer precipitation over Huai river basin with the statistic approach. The results indicate that those soil factors, which are selected by the blending method of dynamical and statistical approaches, are useful for forecasting monthly summer precipitation and can expressly discover their dynamical relationships.