Summer climate variability in China and its association with 500 hPa height and tropical convection

This paper is concerned with interannual and interdecadal variabilities of summer rainfall and temperature patterns in China and their association with 500 hPa height in the Northern Hemisphere (NH), tropical convective activities and global sea surface temperature anomaly (SSTA). The temporal evolutions and spatial structures of interannual variation of summer (JJA) rainfall and temperature from 1951 to 1994 over China are revealed through EOF analysis. The spatial pattern of EOF1 for rainfall (EOF1.R) is dominated by a maximum over the middle-lower reaches of the Yangtze River, and a large negative value region in the middle reach of the Yellow River is also obvious. The spatial pattern of EOF1 for temperature (EOF1.T) reflects coherent variations over most regions of China, and it is dominated by a maximum over the middle-lower reaches of the Yangtze River. Linear increase and decrease trends are found in the time coefficients of EOF1.R and EOF1.T, respectively. The quasi-biennial oscillation (QBO) signal is also strong after the middle of the 1970's in repect of their time coefficients. The coupled patterns of rainfall and temperature are picked up through the singular value decomposition (SVD) analysis. The spatial patterns and their temporal evolutions of SVD1 for rainfall (SVD1.R) and SVD1 for temperature (SVD1.T) are quite similar to those of EOF1.R and EOF1.T. There is an abrupt change in the middle 1970's in the time coefficients of SVD2.R and SVD2.T. The variations of summer rainfall and temperature coupled patterns in China are closely connected with the 500 hPa height anomaly over the Northern Hemisphere (NH). The Pacific-Japan (PJ) and Eurasia (EU) teleconnection patterns play a very important role in the spatial patterns of SVD1.R and SVD1.T, especially in the East Asia monsoon region along the middle-lower reaches of the Yangtze River. The abrupt change of China summer climate in the middle 1970's is related with the intensification and southerly location of the western Pacific subtropical high and also the geopotential height changes over Eurasia and in the regions to the north of the Japan Sea in 1977 or 1978. Correlations between the summer rainfall and temperature coupled patterns and monthly-averaged outgoing longwave radiation (OLR) and high-cloud amount (HCA) data are significant with the PJ teleconnection pattern. There exist positive correlations between the coupled patterns and sea surface temperature anomaly (SSTA) in the North Pacific and the tropical western Pacific. A comparison study shows that there are coherent variations between summer rainfall in the middle-lower reaches of the Yangtze River and in the western part of Japan. It is also demonstrated that there are close correlations between the summer temperature variations in China and in Japan.