Variation in precipitation over Songhua River Basin and its relationship with north Tropical Atlantic sea surface temperature anomalies during boreal spring

Through observation and numerical experiments, this study investigated the variation in the spring precipitation of the Songhua River Basin (SRB) for 1979–2020 and its relationship with the simultaneous northern Tropical Atlantic (NTA) sea surface temperature anomalies (SSTAs). The results show that the main features of atmospheric circulation related to the SRB precipitation were anomalous vorticity over the SRB and the intensity and north boundary position of the West Pacific subtropical high (WPSH). A profound positive relationship existed between SRB precipitation and NTA SSTA during the spring. Further analysis indicated that the divergent wind induced by positive NTA SSTA could generate a Rossby wave source (RWS) over the equatorial and subtropical northern Atlantic. Consequently, a Rossby wave train was excited by the RWS over Eurasia, delivering anomalous wave energy to the SRB and western North Pacific, with two negative anomalous centers in the East European Plain and Northeast China and two positive anomalous centers in the Pamir and West Pacific in the upper troposphere. Thus, the SRB was covered by anomalous cyclones at 850 hPa, and the WPSH became intense and moved northward. As a result, the precipitation over SRB increased. Our results suggest that the spring NTA SSTA can be a potential signal in the prediction of spring SRB precipitation.