Contrasting El Niño impacts on East Asian summer monsoon precipitation between its developing and decaying stages

The different impacts of El Niño on the East Asian summer precipitation (EASP) between its developing and decaying stages are investigated in observations. The EASP responses are almost opposite between the two stages, with an anomalous wet (dry) in Southeast China and an anomalous dry (wet) in North China in the developing (decaying) summer. In the developing summer, El Niño influence on EASP is through its direct impact of the sea surface temperature (SST) anomaly in the tropical Pacific, which induces heating perturbations that excite an upper‐level zonally propagating wave train in mid‐latitude and a lower‐level meridional wave train along the East Asian coast. In contrast, in the decaying summer, El Niño affects EASP through the El Niño‐generated SST anomalies outside the equatorial Pacific, which are combined to produce an uplift of geopotential height around the upper‐level tropics and a lower‐level Pacific‐Japan (PJ) wave train.