Subjects: Geosciences >> Atmospheric Sciences submitted time 2023-12-16 Cooperative journals: 《干旱区研究》
Abstract： Based on daily temperature observation data and reanalysis data of the geopotential height, sea levelpressure, and wind field from 1961 to 2020, the characteristics of spatial and temporal change of cold waves,strong cold waves, and exceptionally strong cold waves lasting 24 h, 48 h, and 72 h were studied in Ningxia overthe past 60 years. The causes of atmospheric circulation anomalies of cold waves were also revealed. The resultsshow the following: (1) In the past 60 years, cold waves of different intensities and different durations in Ningxiaconsistently showed the distribution characteristics of“shifting eastwards and northwards.”(2) The cumulativefrequencies of cold waves, strong cold waves, and exceptionally strong cold waves in the region accounted for71.7%, 22.6%, and 5.7% of the total annual cold wave frequencies, respectively, among which cold wavesdominated by process lasting 24 h and 48 h. The proportions of various durations for strong cold waves andexceptionally strong cold waves were equivalent. They mainly occured in October to April, during which theaccumulated cold waves, strong cold waves, and exceptionally strong cold waves in the region accounted for99%, 98%, and 95% of those throughout the year, and there was a decreasing trend from January to April andincreasing trend from October to December. (3) In the past 60 years, the cold waves, strong cold waves, andexceptionally strong cold waves have been decreasing at a rate of 4.5, 2.8, and 0.18 per station every 10 years,respectively. Among them, the frequencies of waves of 24 h and 48 h as short durations were decreasing, but thatof waves of 72 h as a long duration was decreasing. All types of cold waves decreased from the 1960s to the1990s, reaching a minimum in the 1990s and increasing since the 2000s, with a sudden change around 1990. (4)Under the influence of global warming, the atmospheric circulation showed completely the opposite distributioncharacteristics between before and after the sudden change of cold waves in Ningxia. The key systemsinfluencing cold waves in Ningxia are consistent. When the blocking high pressure in the Ural Mountains wasstronger, the East Asian trough was deeper, the west Pacific subtropical high was weaker, the western side ofLake Baikal was dominated by cyclonic circulation, and cold high pressure at the ground was active, this wasconducive to the southward movement of cold air in middle and high latitudes, and more cold waves in Ningxia.
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