Climatology of Winter Cold Waves and Associated Atmospheric Circulation Anomalies in China During the Last 40 Years

Abstract

Based on daily high-resolution temperature observations at 1941 meteorological stations in China from 1980 to 2023, stations reaching standard for cold wave and 418 cold wave processes (including 152 strong cold waves processes) in winter are identified according to the monitoring indices of cold air processes. And cold wave processes are objectively classified according to their intensity and influencing areas using K-means++ clustering method. The temporal and spatial characteristics of the single-station cold waves and 418 cold wave events are discussed. Results show that the frequency of cold waves in the high affecting areas of China has not increased significantly but has shown a decreasing trend over the last 40 years. The increasing trend of frequency and intensity of single-station cold waves in the middle-lower reaches of the Yangtze River Plain is significant. Additionally, the intensity of single-station cold waves in South China is also noticeably enhanced. The frequency of winter cold wave events in China has decreased significantly in the last 40 years with an expanding range of influence, while the intensity of strong cold wave events has increased significantly, accompanied by a marked increase in the amplitude of interannual variations. The cold air associated with cold waves in China mainly originates from the southeast of Novaya Zemlya, and its trajectory varies depending on the type of cold wave. Based on the fifth-generation European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric reanalysis data (ERA5), characteristics of atmospheric circulation anomalies in the preceding and the simultaneous period for cold wave processes in the countrywide, Northeast-North China and Northwest-North China are analyzed. It is found that the deep warm high pressure in Greenland is an important precursor of the countrywide cold wave, and the zonal wave train in the middle and upper troposphere of Eurasia is a prominent feature of the cold wave outbreak. The cold wave in Northeast-North China is related to the eastward movement of the cold vortex under the block of anomalous high-pressure system in the mid-low latitudes. The cold wave in Northwest-North China is closely related to the development of a warm high ridge over the East European Plain and the circulation situation of two-ridge-one-trough in mid-high latitudes of Eurasia. All types of cold waves are preceded by the maintenance of the Ural blocking high and the accumulation of cold air in Siberia.

Keywords

• cold wave
• tracks of cold air