冬季北美西北部长短冷事件的特征与物理机制

This study investigates the characteristics of long-lived and short-lived cold events in Wes-tern North America using daily NCEP/NCAR reanalysis data, including surface air temperature, temperature at 2-meter(T2m), geopotential height, precipitation, horizontal winds, and vertical velocity. The teleconnection mechanisms associated with the initiation and development of long-lived cold events are systematically analyzed. Based on historical observations from 1982 to 2023, 65 cold events were identified through cumulative T2m anomalies, with 57 classified as short-lived events and 8 as long-lived events according to the probability density function of their durations. The results demonstrate that prolonged cold events exhibit significantly stronger cumulative T2m anomalies compared to short-lived counterparts. Both cold event categories exhibit barotropic dipole anomalies in atmospheric circulation patterns, characterized by low-pressure anomalies over Western North America coupled with adjacent high-pressure anomalies to the west, though the low-pressure systems persist for longer durations during long-livee events. Hemispheric-scale analysis reveals this dipole structure as part of a Rossby wave train. Diabatic heating anomalies over the North Mediterranean, South Japan, and tropical Western Pacific serve as crucial triggers for this wave train, playing a pivotal role in generating and maintaining the low-pressure anomalies over long-lived cold events. The identified teleconnection impacts of Rossby wave trains on wintertime long-lived cold events provide valuable scientific references for improving extended-range cold weather forecasting in this region.