关键词: 中亚干旱区, 降水突变, 西风环流, TBO

Abstract: This study analyzed tropospheric biennial oscillations (TBO) and abrupt changes of precipitation in the arid Central Asia (ACA) and their regional differences during 1930-2009 using the monthly 0.5°×0.5°gridded precipitation data from Climatic Research Unit (CRU) and the NCEP/NCAR monthly 2.5°×2.5° gridded geopotential height reanalysis data in 1948-2009. The results show that precipitation in ACA has significant TBO. The TBO of annual precipitation continued during 1930-2009 in subregions I (West Kazakhstan region), II (East Kazakhstan region) and IV (Kyrgyzstan region). However, there was an opposite trend in the intensity changes of TBO between sub-regions III (Central Asia Plains region) and V (Iran Plateau region) before and after the 1960s-1970s. The TBO of annual precipitation mainly resulted from winter precipitation in most of the sub-regions, except sub-region II where it mainly resulted from summer precipitation. Additionally, the temporally abrupt changes of precipitation were in good agreement with TBO signal changes in ACA, the periodicity of precipitation at abrupt change points all turned into TBO. From the perspective of the whole ACA region, abrupt change of precipitation occurred in western ACA in early 1950s, in eastern ACA in late 1960s and in Xinjiang in late 1980s, respectively. Although the precipitation’s TBO was observed in both the monsoon regions of East Asia and the arid Asian inland region where the westerlies dominated, the forcing factors might differ from each other. The quasi-biennial oscillation (QBO) of westerly wind circulation in the middle-upper troposphere might be one of the major factors that influence the TBO of precipitation in ACA.

Key words: arid Central Asia, abrupt change of precipitation, westerly wind circulation, TBO