第一届未来大气科学论坛

During the boreal winter of 2023/24, persistent precipitation with cold-air outbreaks over the Yangtze River basin (YRB) resulted in severe compound cold–wet events, causing disastrous impacts on local transportation and agriculture. The subseasonal causes of these persistent extreme events remain unclear. Our findings revealed that the phase of the surface air temperature (SAT) intraseasonal oscillation (ISO) preceded the counterpart of precipitation by 4–5 days, indicating its dominant role in regulating precipitation anomalies over the YRB. The phase of SAT anomalies can be attributed to Rossby wave trains originating from the Arctic and midlatitude North Atlantic. The 10–30-day ISO of the Arctic Oscillation (AO) index leads SAT and precipitation anomalies in the YRB by 3–8 days, serving as a precursor signal of these anomalies. Moreover, strong Madden–Julian oscillation (MJO) is favorable for the precipitation ISO events. Historical analyses show that since the winter of 1979/80, when winter AO index exhibited strong 10–30-day ISO, both ISO of SAT and AO anomalies have undergone sign reversals during wet and dry processes, accompanied by the asymmetric impact of the MJO. Following the peak of wet (dry) ISO events, colder (warmer) SAT anomalies enhanced the likelihood of compound cold–wet (warm–dry) events. Therefore, the 10–30-day AO can be considered a valuable precursor signal for subseasonal predictions for compound events in the YRB during the boreal winter.
 

compound cold–wet events,the Yangtze River basin,intraseasonal oscillation,Arctic Oscillation,precursor signal