Three leading coupled modes of summer rainfall with atmospheric circulations over northern East Asia

Abstract

Northern East Asia (NEA) is characterized by wet monsoon region in the east and mid‐latitude westerly‐controlled dry inland in the west in summer, where ecosystem and environment are vulnerable to rainfall variability. Previous studies found close relationship between summer rainfall in NEA and local large‐scale atmospheric circulation systems including East Asian upper‐tropospheric westerly jet (EAJ) and middle‐tropospheric trough (EAT), and lower‐tropospheric low over NEA (NEAL). However, major features of rainfall–circulation coupling over NEA are still not fully understood. This study addresses this issue using multivariate empirical orthogonal functions method based on the ERA‐Interim reanalysis dataset and the GPCP precipitation data for 1979–2018. Three leading coupled modes are identified, together accounting for 30–50% of summer rainfall year‐to‐year variance in most of NEA. The first mode features consistent decrease of rainfall in NEA related to the decelerated EAJ, southward shifted EAT, and weakened NEAL, with a significant interdecadal change in late 1990s. The second mode exhibits a meridional dipole rainfall pattern, with less rainfall along the East Asian subtropical rainy belt and more rainfall in southern Russian Far East, coupled with the northward shifted EAJ, weakened EAT, and intensified NEAL. The third mode presents a zonal dipole rainfall pattern, with suppressed rainfall in southern Russia east of northeast China and enhanced rainfall around the Lake Baikal related to the decelerated EAJ, and westward shifted EAT and NEAL. Further investigation shows that the first mode is remotely modulated by summer rainfall anomalies in the Sahel region and Atlantic Multidecadal Oscillation (AMO) on the interdecadal timescales, and by the Polar/Eurasia teleconnection on the interannual timescales. The second and third modes are, respectively, modulated by summer rainfall in the western North Pacific and north central‐eastern India through the East Asia‐Pacific and circumglobal teleconnection patterns.