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In order to study the characteristics of low frequency oscillation of summer precipitation over Qinghai-Xizang Plateau， based on the daily precipitation data of 62 meteorological stations over the Qinghai-Xizang Plateau from 1978 to 2017 and the high-resolution daily reanalysis data of ERA5.This paper adopted the collection of empirical mode decomposition （EEMD）， Lanczos filter and synthesis analysis method.Filter out the years of drought and flood， and analyzed the characteristics of low frequency oscillation， variation of meteorological elements and circulation of precipitation in dry and flood years in summer over the Qinghai-Xizang Plateau.Reveals the drought and flood years， the characteristics of low frequency oscillation period of precipitation in plateau area， the circulation characteristics and low frequency and other transmission characteristics of wind field and vorticity field.The results show that： （1） There is an oscillation period of 10~20 days in summer precipitation over the Qinghai-Xizang Plateau.The period frequency of drought and flood years is different， the oscillation frequency of flood years is obviously higher than that of drought years.In flood years， the significant oscillation is 10~20 days and 30-days oscillation， while in drought years， the oscillation is mainly 10~20 days.（2） In flood years， the low-frequency precipitation phase is strong， the high-altitude low-frequency cyclones control the plateau， the high-altitude divergence， the low-altitude convergence.The water vapor supply from the south of the Bay of Bengal， and the low-frequency disturbance is strong， which is conducive to the occurrence of precipitation， there is an abnormal circulation distribution of low-frequency anticyclone- low-frequency cyclone- low-frequency anticyclone from west to east.On the contrary， in the low frequency precipitation weak phase， the high frequency anticyclone controlled the main body of the plateau， high altitude convergence， low altitude divergence， the warm and wet southerly air is weak， the disturbance is weak， not conducive to the occurrence of precipitation.The distribution of low-frequency anticyclone， low-frequency cyclones and low-frequency anticyclone is not obvious in drought years， and the oscillation intensity is not as strong as that in flood years， and the intensity of low-frequency element field is weak.（3） The transmission of low-frequency fluctuation is different in drought and flood years.In flood years， the high and low plateau is the sink area of low-frequency oscillation， and the meridian is also the convergence area.The precipitation in the oscillation sink area is more frequent， so the precipitation in flood years is more.In the dry years， the low-frequency oscillation propagates upward from the plateau to the upper level， so the low-frequency precipitation occurs less in the dry years.

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Soil moisture is a key parameter in the prediction of southwest monsoon rainfall, hydrological modelling, and many other environmental studies. The studies on relationship between the soil moisture and rainfall in the Indian subcontinent are very limited; hence, the present study focuses the association between rainfall and soil moisture during different monsoon seasons. The soil moisture data used for this study are the ESA (European Space Agency) merged product derived from four passive and two active microwave sensors spanning over the period 1979-2013. The rainfall data used are India Meteorological Department gridded daily data. Both of these data sets are having a spatial resolution of 0.25° latitude-longitude grid. The study revealed that the soil moisture is higher during the southwest monsoon period similar to rainfall and during the pre-monsoon period, the soil moisture is lower. The annual cycle of both the soil moisture and rainfall has the similitude of monomodal variation with a peak during the month of August. The interannual variability of soil moisture and rainfall shows that they are linearly related with each other, even though they are not matched exactly for individual years. The study of extremes also exhibits the surplus amount of soil moisture during wet monsoon years and also the regions of surplus soil moisture are well coherent with the areas of high rainfall. [ABSTRACT FROM AUTHOR]