Interannual variability of Mascarene high and Australian high and their influences on summer rainfall over East Asia

Based on the reanalysis data from NCEP/NCAR and other observational data, interannual variability of Mascarene high (MH) and Australian high (AH) from 1970 to 1999 is examined. It is shown that interannual variability of MH is dominated by the Antarctic oscillation (AAO), when the circumpolar low in the high southern latitudes deepens, the intensity of MH will be intensified. On the other hand, AH is correlated by AAO as well as El Nino and South Oscillation (ENSO), the intensity of AH will be intensified when El Nino occurs. Both correlation analysis and case study demonstrate that summer rainfall over East Asia is closely related to MH and AH. When MH intensifies from boreal spring to summer (i.e. from austral autumn to winter), there is more rainfall over regions from the Yangtze River valley to Japan, in contrast, less rainfall is found over southern China and western Pacific to the east of Taiwan, and most of regions in mid-latitudes of East Asia. Compared with MH, the effect of AH on summer rainfall in East Asia is limited to localized regions, there is more rainfall over southern China with the intensification of AH. The results in this study show that AAO is a strong signal on interannual time-scale, which plays an important role in summer rainfall over East Asia. This discovery is of real importance to revealing the physical mechanism of interannual variability of East Asian summer monsoon and prediction of summer precipitation in China.