THE MECHANISM OF THICKNESS OF GEOPOTENTIAL HEIGHT DIPOLE AND ITS RELATION WITH CLIMATE VARIABILITY IN ASIA-AUSTRALIA IN BOREAL WINTER

With the EOF of reanalysis data being analyzed, a northern-southern dipole is found in the upper troposphere geopotential height field of over the Asian-Australian monsoon region in the winter of the Northern Hemisphere(NH),which is defined as Asian-Australian dipole(AAD) in this study. Its intensity index is defined as AADI. Correlation and synthetic analysis illustrate that AADI is closely related to the weather and climate of Asian-Australian region in boreal winter. The index can reflect the simultaneous anomalies of temperature and precipitation on interannual and decadal scales in the boreal winter of Asian-Australian region. The superposition of the decadal and interannual signals is significant for the relationship between the AADI and climate change. The index can be used as an indicator of intensity of the Asian-Australian monsoon. In the years of strong AADI, the East Asia major deep trough is stronger,the Subtropical High is weaker and the Alaska ridge and the westerly jet are stronger than those in normal years.Enhanced meridional circulation between high and low latitudes exists in the years of strong AADI. These relationships reflect the intrinsic link between the anomalies in the upper troposphere geopotential height and climate in the Asian-Australian region.