Spatial and Temporal Variation of Summer Precipitation over the Eastern Tibetan Plateau and the North Atlantic Oscillation

Abstract

Abstract The interannual variability of summer precipitation over the eastern Tibetan Plateau (ETP) was examined in relation to the Northern Hemisphere macroscale circulation patterns during the period 1961–90. Summer precipitation data for 66 stations located above 2000 m MSL are used in the analysis. Using principal component analysis, it is found that the dominant spatial pattern of interannual variability of the summer precipitation is a seesaw structure between the southern and northern parts of ETP. Correlation analysis shows that this pattern of precipitation anomalies is closely associated with the North Atlantic oscillation (NAO). Further analysis based on midtropospheric geopotential height and wind data suggests the upstream zonal flow variation associated with the NAO pattern as the major mechanism linking the regional precipitation fluctuation to macroscale circulation conditions. During the summers of low NAO index values, the westerly winds between 40° and 50°N from the eastern Atlantic to ...