1951—2017年冬季中国南方持续性冰冻雨雪事件的气候特征及其与环流异常的联系

采用1950—2018年中国753站逐日气温和降水资料及NCEP/NCAR逐日再分析资料，确定了1951—2017年冬季中国南方强持续性冰冻雨雪事件，并对其时空特征、区划及事件爆发日的环流特征进行分析。结果表明：1）中国南方持续性冰冻雨雪事件存在显著的2～3 a周期变化，且1985年前后发生了突变，虽然近年来其强度呈显著减弱趋势，但仍然发生了多次强持续性冰冻雨雪事件；2）持续性冰冻雨雪事件在中国南方中西部发生频次高、持续日数长，在中国南方中东部则强度更大；3）中国南方37次强持续性冰冻雨雪事件可划分为华中型、华南型和西南型3类；4）3类持续性冰冻雨雪事件爆发日，欧亚大陆500 hPa位势高度异常呈现北高南低，蒙古高压显著偏强、中心南进，该配置有利于北方冷空气向南输送，且南支槽显著加深，水汽向北输送活跃。三者的不同之处在于蒙古高压强度及影响范围存在差异，其中西南型最强、范围最大、南伸显著，华南型次之；华中型、华南型的水汽输送受南支槽和副热带高压共同影响，而西南型的水汽输送仅受南支槽调控。

Climatic characteristics of winter long-lasting freezing rain and snow events in southern China from 1951 to 2017 and their relationship with circulation anomalies

Based on the daily temperature and precipitation data of 753 stations in China and NCEP/NCAR daily reanalysis data from 1950 to 2018, the strong long-lasting freezing rain and snow events in southern China in winter from 1951 to 2017 are determined, and their temporal and spatial characteristics, divisions and circulation characteristics on the event outbreak day are analyzed.Results show that:1) The long-lasting freezing rain and snow events in southern China have a significant 2-3 a cycle change, and an abrupt change occurred around 1985.Although their intensity has decreased significantly in recent years, there are still many strong long-lasting freezing rain and snow events.2) The long-lasting freezing rain and snow events occur frequently and last for a long time in the central and western parts of southern China, while the intensity is greater in the middle and eastern parts of southern China.3) The 37 strong long-lasting freezing rain and snow events in southern China can be divided into three types:Central China type, South China type and Southwest China type.4) On the outbreak day of three types of long-lasting freezing rain and snow events, 500 hPa geopotential height anomalies in Eurasia are high in the north and low in the south, the Mongolian high is significantly stronger with the center moving southward, and this configuration is conducive to the southward transportation of cold air in the north;In addition, the South Branch trough is significantly deepened, and the water vapor is actively transported to the north.The difference among the three types is that there are differences in the intensity and influence range of Mongolian high, among which Southwest China type is the strongest with the largest range and significant south extension, followed by South China type.The water vapor transport of Central China type and South China type is jointly affected by the South Branch trough and subtropical high, while the water vapor transport of Southwest China type is only controlled by the South Branch trough.