South-North dipole in summer precipitation over Northeast China

This study discusses the interannual variability and influencing mechanisms of the summer precipitation dipole pattern in Northeast China from 1961 to 2020 based on observation data and reanalysis data. Results indicate that the second mode of empirical orthogonal function (EOF2) mode of summer (June-August) precipitation in Northeast China presents a dipole pattern with opposite trends in the north and south, and its time series (PC2) demonstrates significant interannual variations. The South-North dipole pattern in summer precipitation over Northeast China are significantly correlated with the tropical sea surface temperature, Arctic sea ice, and Eurasian snow cover in the preceding spring (March-May) on an interannual scale. In the preceding spring, the rise in sea temperature in the eastern equatorial Pacific and the decline in the western equatorial Pacific can stimulate EAP and EU teleconnections, positioning a cyclonic center over Northeast China, thereby influencing the dipole pattern of precipitation in Northeast China. Furthermore, the anomalies in European snow cover and Arctic sea ice can lead to an increase in albedo and a decrease in upward heat flux, causing the lower atmospheric temperature to drop and persist into the summer. This triggers the eastward propagation of atmospheric Rossby waves at mid-high latitudes, which promotes precipitation in Northeast China through the occurrence of negative potential height anomalies. These conditions influence the anomalies in the atmospheric circulation over the Eurasian continent, regulate moisture transport and vertical motion, and collectively contribute to the dipole pattern of summer precipitation in Northeast China over the past 60 years, with opposite trends in the north and south.