Joint Effect of East Asia–Pacific and Eurasian Teleconnections on the Summer Precipitation in North Asia

The East Asia–Pacific (EAP) and Eurasian (EU) teleconnections are independent of each other on the seasonal timescale (with a correlation coefficient of only 0.03). But they may occur concurrently with consistent or opposite phases. This paper investigates their synergistic effect on the summer precipitation in North Asia. Based on the signs/phases of EAP and EU indices, the EAP and EU teleconnection anomalies occur in four cases: (I) positive EAP + positive EU, (II) negative EAP + negative EU, (III) positive EAP + negative EU, and (IV) negative EAP + positive EU. Further analyses show that these four configurations of EAP and EU anomalies are coherently related to different atmospheric circulations over the midlatitude Eurasian continent, leading to different summer precipitation modes in North Asia. Category I (II) corresponds to a zonal tripole structure of the geopotential height at 500 hPa over eastern Europe and the Sea of Japan, leading to less (more) than normal precipitation in eastern Europe, Japan, and the surrounding areas, and more (less) precipitation from central China to Lake Baikal and eastern Russia. Category III (IV) corresponds to a meridional dipole structure of the geopotential height at 500 hPa over North Asia, leading to more (less) precipitation in the northern North Asia and less (more) precipitation in most of the southern North Asia. Independent analysis reveals that the EAP teleconnection itself is positively correlated with the precipitation in the region between the eastern part of Lake Baikal and Okhotsk Sea, and negatively correlated with the precipitation in the region between Northeast China and Japan. Coincidently, the EU pattern and precipitation have negative correlations in Ural Mountain and Okhotsk Sea areas and positive correlations in the Lake Baikal area. The respective relations of EAP and EU with the summer precipitation in North Asia suggest that the EAP northern lobe overlapped with the EU central and eastern lobes could extend the geopotential anomalies over Lake Baikal to Russian Far East, creating an EAP–EU synergistic effect on the summer precipitation in North Asia.