Combined impact of in-phase and out-of-phase variation between the northern East Asian low and western North Pacific subtropical high on East Asian summer rainfall

Abstract

East Asian summer rainfall is affected by both the continental northern East Asian low (NEAL) and the western North Pacific subtropical high (WNPSH) in the lower troposphere. This study investigates the joint effect of the two circulation factors on East Asian summer rainfall. It is found that the rainfall in East Asia behaves differently in the years with in-phase and out-of-phase variation between the NEAL and WNPSH. When the NEAL and WNPSH vary in phase, i.e. when they are both stronger, the rainfall anomaly shows a dipole pattern in East Asia and displays opposite changes between north and south of 30°N. When the two circulation factors vary out of phase, the rainfall anomaly is concentrated in the Yangtze River valley.