云南东北部冻雨的气候特征及影响因素研究
Study on Climatic Characteristics and Influencing Factors of Freezing Rain in Northeast Yunnan Province

本文依据1991~2021年云南东北部冻雨相关观测日值数据，分析了云南东北部冻雨发生的气候特征和影响因素。结果表明：云南东北部冻雨主要发生在12月至1月。发生次数总体呈现减弱趋势，在2014/2015年出现显著突变，由偏多转变为偏少。在冻雨偏多时乌拉尔山附近阻塞高压和切断低压偏强，整个北极和西南地区位势高度呈现负距平，欧亚地区温度场大范围呈现负距平，欧洲东部呈现强烈的反气旋式环流，有利于冷空气从极地向西伯利亚移动；在冻雨偏少时，阻塞低压的位置偏东，位势高度和温度场异常与偏多年相反。冻雨发生与赤道中东太平洋海区La Niňa型和北大西洋三极子型的海温异常有关。1991~2014年冻雨的发生次数与赤道中东太平洋海温关系较为明显，2015~2021年冻雨的发生次数与西北太平洋海温和巴芬湾的海冰关系较为明显。分别建立冻雨的预报模型，发现对2015~2021年冻雨的发生次数的模拟较好。
Based on the observed daily values of freezing rain in northeast Yunnan from 1991 to 2021, the climatic characteristics and influencing factors of freezing rain in northeast Yunnan were analyzed in this paper. The results show that the freezing rain mainly occurs from December to January in northeast Yunnan. The frequency of occurrence generally showed a weakening trend, and there was a significant mutation in 2014/2015, which changed from more to less. When there is more freezing rain, the blocking high and cutting low near the Ural Mountains are stronger, the geopothetic height of the whole Arctic and southwest China presents a negative anomaly, the temperature field in Eurasia presents a negative anomaly in a wide range, and the eastern Europe presents a strong anticyclonic circulation, which is conducive to the movement of cold air from the polar regions to Siberia. When there is less freezing rain, the blocking low is located to the east, and the geopotentic height and temperature field anomalies are opposite to those in the past few years. The occurrence of freezing rain is associated with sea surface temperature (SST) anomalies of La Niňa type in the equatorial Middle Eastern Pacific and the North Atlantic tripole type. The relationship between the occurrence of freezing rain and SST in the equatorial Middle East Pacific from 1991 to 2014 is obvious, and the relationship between the occurrence of freezing rain and the SST in the Northwest Pacific and the sea ice in Baffin Bay from 2015 to 2021 is obvious. The forecast model of freezing rain is established respectively, and it is found that the simulation of freezing rain occurrence times from 2015 to 2021 is better.