The Relationship between Summer Precipitation Anomaly in North China, Atmospheric Circulation and SST

Using the gridded precipitation data from Chinese ground meteorological stations, the NOAA monthly sea surface temperature (SST) data, and the NCEP/NCAR monthly mean reanalysis data from 1961-2015, and with EOF, correlation analysis, and synthetic analysis, we analyze the relationship between summer precipitation, atmospheric circulation and SST in North China, as well as the influence of the winter EP-type El Niño index (I_EP) on summer precipitation in North China in the following year.The results show that the circulation characteristics of the increased (decreased) summer precipitation in North China are negative (positive) geopotential height anomaly in Lake Baikal, a positive (negative) anomalous center in the North Pacific Ocean, and a strengthening (weakening) positive geopotential height anomaly from the Sea of Japan to the Bohai Sea, which is typical of the east-high (low) west-low (high) circulation in the East Asian region.There is an anomaly of key SSTs in the east-central equatorial Pacific Ocean in the same period of summer precipitation in North China, exhibiting a significant negative correlation, which means that the increased (decreased) SST in the key area is correlated to the decreased (increased) summer precipitation in North China.Positive phase years of winter I_EP index are accompanied with positive anomaly of summer precipitation in North China in the following year, while significant negative anomaly is identified at 500 hPa over Northwest Pacific Ocean.The circulation type of two ridges and a trough type appears in the middle and high latitudes.The subtropical high pressure in the western Pacific Ocean shifts more westward than the climatic state.Obvious anomalous easterly wind is found in the equatorial west Pacific.The vertical uplift movement in the low level provides favorable dynamic conditions for the transport of water vapor in the meridional channel of the Bay of Bengal and the latitudinal channel of the Pacific Ocean, which is conducive to the increased precipitation in the rainy season in North China; The opposite situation occurs in the negative phase years of the I_EP index.