ISSN 1000-0526
CN 11-2282/P
CN 11-2282/P
Causes and Predictability of the High-Impact Large-Scale Cryogenic Freezing Rain and Snow Weather in East China and Central China in February 2024
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Abstract:
The causes and predictability of the high-impact large-scale cryogenic freezing rain and snow weather (CFRSW) in East China and Central China in February 2024 are investigated with the daily temperature and precipitation data from 2374 stations, the NCEP/NCAR atmospheric circulation reanalysis data and the HadISST data. The results show that the two CFRSW processes occurred in China in early and late February 2024, and the overlap of the disaster-hit regions was high so that East China and Central China suffered the most serious freezing rain and snow disaster. The subtropical and mid-high latitude circulation system configurations that impacted the two CFRSW processes were more consistent, the Northwest Pacific subtropical high was stronger and more westward. Moreover, the Siberian high, the South Branch trough and the Northwest Pacific anticyclone were stronger in the same period, forming a strong synergistic effect. The enhancement of the Siberian high led to cold air southward, and the synchronization of the enhancement of South Branch trough and western North Pacific anticyclone provided abundant water vapor conditions for East China and Central China. A moderate-intensity El Nino event occurred in the equatorial east-central Pacific from May 2023 to April 2024. In addition, the tropical Indian Ocean and the tropical North Atlantic were abnormally warm in winter. The abnormal SST of the three oceans jointly led to the continuous strengthening of the Northwest Pacific subtropical high. This was conductive to the periodic development and enhancement of the anticyclones in the Northwest Pacific Ocean, and provided abundant water vapor conditions for the two CFRSW processes in February 2024. The predictability of the sub-seasonal model for the two processes is about 1-2 weeks ahead of time, and the prediction skill within 1 week is relatively high. When the prediction is advanced by more than 2 weeks, the model is unable to accurately predict the anomalous characteristics of the Eurasian mid-high latitude circulation system, resulting in lower predictive ability for the two processes.
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