Intercomparison of the impacts of four summer teleconnections over Eurasia on East Asian rainfall

Abstract

East Asian summer climate is strongly affected by extratropical circulation disturbances. In this study, impacts of four atmospheric teleconnections over Eurasia on East Asian summer rainfall are investigated using National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data and Climatic Research Unit (CRU) land precipitation data during 1979-2009. The four teleconnections include the Scandinavian (SCA), the Polar/ Eurasian (PEU), the East Atlantic/Western Russian (EAWR), and the circumglobal teleconnection (CGT). Moreover, the related changes of lower-tropospheric circulation are explored, specifically, the low pressure over northern East Asia (NEAL) and the subtropical high over the western North Pacific (WNPSH). The results presented are in the positive phase. The PEU and SCA induce significant negative anomalies in North China rainfall (NCR), while the CGT induces significant positive anomalies. In the past three decades, the PEU and SCA explain more than 20% of the variance in NCR, twice that explained by the CGT, suggesting a more important role of the former two teleconnections in NCR variation than the latter one. Mean-while, the PEU and SCA reduce rainfall in Northeast China and South Korea, respectively, and the CGT enhances rainfall in Japan. The rainfall responses are attributed to the SCA-induced northward shift of the NEAL, and PEU-induced northward shift and weakening of the NEAL, respectively. For the CGT, the dipole pattern of rainfall anomalies between North China and Japan is affected by both westward extension of the NEAL and northwestward expansion of the WNPSH. In addition, the EAWR leads to an increase of sporadic rainfall in South China as a result of the eastward retreat of the WNPSH.