黔东北2021年9月异常高温成因分析OA

Based on the monthly mean temperature observation data from national surface meteorological stations in Northeastern Guizhou from 1961 to September 2023,this study analyzed the climatic characteristics of September in this region.Furthermore,using NCEP reanalysis data from 1991 to 2021,the circulation characteristics such as geopotential height field,horizontal wind field and sea level pressure field under high temperature conditions in September were examined to explore the formation mechanisms of high temperatures.The results showed that the study region was dominated by low-temperature anomalies from the 1960s to the 1980s,while high temperature anomalies prevailed from the 1990 to 2023.Notably,the temperature in September 2021 was abnormally high by 3.1℃,with high temperatures mainly occurring in the early and late dekads of the month.Circulation analysis indicated that the abnormally high average temperature in northeastern Guizhou in September 2021 was mainly caused by the stronger intensity,larger extent,more westward extension ridge point and northward shifted ridge line of the Western Pacific Subtropical High,which exerted prolonged control over the region.The upper-level westerly jet core was located 5° north of the climatological mean,which inhibited the southward intrusion of westerly disturbances into low-latitude areas.In addition,the lower-level wind field exerted a significant influence on air mass activities,characterized by prominent southwesterly wind anomalies that facilitated the northward transport of warm air from the south.Moreover,A significant negative anomaly zone extends from the region of 60°-75° N,70°-130° E to the areas of 35°-55° N,110°-120° E and 20°-50° N,120°-150° E,accompanied by negative anomalies in Northeast China and Eastern Europe,which were unfavorable for the southward movement of cold air,thus providing favorable conditions for the occurrence and development of persistent anomalous high temperatures throughout the month.The results provide a reference for local high-temperature early warning and agricultural production decision-making.