1961~2019年贵阳冬季凝冻时空特征与异常成因

利用1961~2019年贵阳8个地面观测站冬季（12月~次年2月）雨凇观测资料和北半球500hPa高度场、全球气温场及欧亚水平风场资料，通过EOF、M-K、小波及合成分析方法，对贵阳冬季凝冻日数的时空特征及其与北半球500hPa高度场、全球海温场及欧亚水平风场的关系进行了探讨。结果表明:近59年贵阳市冬季及各月平均凝冻日数为10.7d，由西南部向东北部逐渐增多，开阳东北部凝冻日数达到20d以上；凝冻日数变化趋势具有高度一致性，12月与冬季凝冻日数变化为显著正相关，突变多发于20世纪70~80年代末，在1980~1990年及2005~2015年出现4a的显著周期变化；强凝冻年500hPa高度距平合成场欧亚大陆的位势高度呈现“北高南低”分布，强弱年差值距平场欧亚大陆中高纬地区表现为“北正南负”，北半球高纬度地区格陵兰、北美及乌拉尔山-西伯利亚一带为正距平；强凝冻年赤道中东太平洋秋季海温距平为负，引起纬向环流加强，水汽交换增加；高层辐散低层辐合以及偏北强风带南下低空冷锋生成，利于西南水汽输送到云贵高原东北部与北方的冷空气交汇，为凝冻产生创造了条件。 

Analysis on Temporal and Spatial Characteristics and the Causes of Typical Freezing in Guiyang from 1961 to 2019

Using the rime observation data of 8 observation stations in Guiyang from 1961 to 2019, and the 500 hPa height field data in the Northern Hemisphere, the global temperature field data and the Eurasian horizontal wind field data, the space-time distribution characteristics of freezing rain days and the relationships with the 500hPa height field in the Northern Hemisphere, sea surface temperature field and Eurasian horizontal wind field were analyzed with EOF, M-K, wavelet analysis and composite analysis methods. The results show that the average freezing rain days are 10.7d in Guiyang in recent 59 years, and increasing gradually from the southwest to the northeast, and the freezing days in the northeast of Kaiyang reach over 20 days. The variation trend of freezing days is highly consistent, and most of the abrupt changes occur in the late 1970s to 1980s. It occurs significant periodic change of 4-year-cycle during the period of 1980~1990 and 2005~2015. The resultant field of 500hPa height anomaly in strong freezing year shows a distribution of "high in the north, low in the south" in Eurasian continent. The field of strong and weak annual difference anomaly is "positive in the north, negative in the south" in Eurasian mid-high latitudes, and positive anomaly in the high latitudes of the northern Hemisphere, include Greenland, North America and Urals-Siberia. In a strong freezing year, the autumn SST anomaly of the equatorial Middle East Pacific is negative, which causes the strengthening of zonal circulation and the increase of water vapor exchange. The divergence in the upper layer and convergence in the lower layer as well as the formation of a low cold front in the northerly strong wind belt are favorable for the southwest moisture transporting to the northeast of the Yunnan-Guizhou Plateau to meet with the cold air from the north.