Possible Mechanism About Effect of Interannual Variation of Australia Summer Heat Low on Winter Rainfall in Southern China

Abstract

The Southern Hemisphere( SH) atmospheric circulation is an important part of the global atmospheric circulation and a key factor to influence the global climate change and East Asian monsoon system. In winter of the Northern Hemisphere( NH),the intensity changes of Australia summer heat low which is one of East Asia and Indonesia-Northern Australia winter monsoon systems in the low level has great influence on winter rainfall in Southern China. Based on the monthly precipitation at 160 weather stations in China since 1951 and NCEP / NCAR reanalysis data,the anomalous intensity events of Australia summer heat low from 1961 to 2013 were selected,firstly. The relation between the interannual change of Australia summer heat low and winter precipitation in southern China was found,and on this basis the possible influencing mechanism of the Australia summer heat low on winter rainfall in southern China also was analyzed. Results showed that the Australia summer heat low had significant effect on winter rainfall in southern China in NH winter,and there was a negative correlation between them. When the Australia summer heat low was stronger than normal,the precipitation in southern China would be significantly less. Conversely,when it was weaker,the precipitation would be more. When the Australia summer heat low was anomalous stronger than normal,the East Asia Trough on 500 h Pa strengthened,the subtropical high weakened,winter monsoon enhanced,and the region in southern China was influenced by the anomalous northerly airflow and downward airflow,the water vapor transport was poor,so it was not conducive to rainfall. In addition,the anomalous cyclonic circulation over the South China Sea formed due to the anomalous westerlies near the equator through the lateral coupling effect,and then the abnormal northerly wind appeared in the low and middle layer of the southern area,which was not help to rainfall in winter. When the Australia summer heat low was anomalous weaker than normal,it was the opposite.