Synergistic role of Atlantic SST and southern Russian steppe precipitation in subseasonal heat prediction over the Yangtze River Basin
摘要
As a major environmental hazard, heat events can significantly impact human health, ecosystems, and social services. The accurate prediction of heat events at subseasonal timescales is essential for the mitigation of disasters. Based on observational data and reforecast data retrieved from the North American Multi-Model Ensemble (NMME) project, this study investigated the synergistic effect of the negative SST anomaly (SST–) over the central North Atlantic and the positive precipitation anomaly (PREC+) over the Southern Russian Steppe in June on the subseasonal heat prediction skill and the observed monthly maximum temperature (Tmax) in August over the Yangtze River Basin (YRB). The results first demonstrate that the NMME subseasonal heat prediction is unable to accurately reproduce the response to the forcing of two factors, indicating a lack of precision that NMME could be enhanced. The composite analysis of circulation further illustrates that the joint events can synergistically diminish the YRB Tmax in August through non-linear physical processes and then amplify the NMME subseasonal prediction bias. In particular, the inactive subseasonal wave activity over the mid-latitudes at the upper troposphere, the weakened Western North Pacific subtropical high, and the strengthened cyclonic anomalies at the lower troposphere are the principal processes responsible for the synergistic effect of SST– and PREC+. This study identifies the potential subseasonal precursors for the heat prediction over the YRB. It suggests that advancing subseasonal prediction should consider the synergistic effects of different land and sea signals in the preceding period.