1991-2020年重庆市倒春寒时空变化及其异常年大气环流背景分析OACSTPCD

Daily temperature data from 34 observation stations in Chongqing from 1991 to 2020,NCEP/NCAR re-analysis data,NOAA sea surface temperature data,and 130 atmospheric circulation parameters from the National Climate Center were utilized.Trend analysis and empirical orthogonal function decomposition methods were em-ployed to analyze the spatiotemporal characteristics of late spring cold events in Chongqing,the atmospheric circu-lation and the preceding sea temperature features in anomalous years.The results indicated that the occurrence of late spring cold events in Chongqing exhibits significant spatial and temporal differences.The period 2001-2010 had the fewest occurrences but the strongest intensity.The southwestern part of Chongqing experienced the most frequent and the strongest late spring cold events.The primary spatial pattern of change in late spring cold event occurrences is characterized by a consistent anomaly distribution.In spring,the Ural high-pressure ridge is abnor-mally enhanced,while the 500 hPa geopotential height field is anomalously low from the Black Sea to Xinjiang,China,the Qinghai-Xizang Plateau,and most of China.The negative 700 hPa temperature anomaly is observed from the Ural Mountains to most of China.The westerly circulation from the Black Sea to Siberia is weakened,and the meridional circulation in the mid-high latitudes is significantly enhanced,facilitating the southward movement of cold air.This constitutes the main atmospheric circulation background for the occurrence of late spring cold e-vent in Chongqing.Additionally,warmer(colder)sea surface temperatures in the Western Pacific Warm Pool and the Bay of Bengal during the preceding winter are correlated with fewer(more)occurrences of late spring cold e-vents in Chongqing.