2011年初云南东部极端低温冰冻灾害天气气候特征及成因分析

利用NCEP/NCAA再分析资料,国家气候中心74项环流指数及云南省122个观测站资料,结合诊断、合成和相关分析等方法,探讨2011年初云南东部极端低温冰冻灾害天气气候特征及成因,并与2008年初低温冰冻灾害进行对比分析。旨在寻找云南低温冰冻天气的预报着眼点,为提前做好防灾减灾工作提供决策依据。研究表明:500hPa高度场欧亚中高纬呈两槽一脊,西西伯利亚高压脊异常强大,贝巴之间为东西向横槽,东亚中高纬呈"+-+"的高度场距平分布,西太平洋副热带高压异常偏东偏弱,南海副高异常偏南偏弱是2011年1月云南东部频遭冷空气影响的大尺度大气环流背景。另外,相关分析发现NINO4区海温持续异常偏冷对应云南东部气温异常偏低。较2008年初持续近2个月的低温雨雪冰冻灾害相比,虽然2011年灾害影响时间较短,范围较小,但冷空气过程频发,昆明准静止锋长时间控制云南东部,最终造成近50年来的极端低温冰冻灾害。

Feature of Weather and Climate and Cause Analysis of Extreme Cold and Feezing Weather in East Yunnan in Early 2011

Using the NCEP and NCAA reanalysis data,the 74 circulation index of the National Climate Center and the observatory data of 122 stations in Yunnan province,we analyzed the feature of weather and climate and cause of extreme cold and freezing weather.And the difference characteristics of freeze disaster in 2011 and early 2008 were compared and analyzed.The purpose is to find the focus of attention about the cold and freezing weather forecasting and offer the decision basis for disaster prevention and mitigation work in advance.These studies were based on the methods of diagnosis,composite analysis and correlative analysis.Studies showed that the large-scale atmospheric circulation anomaly gave rise to the continuous low temperature and freezing weather.The abnormal atmospheric circulation appeared in mid-high latitude had two troughs and one-ridge in European-Asian region of 500-hPa geopotential height field.There was stronger high pressure ridge in West Siberian.The east-west direction horizontal trough during Balkhash Lake and Baikal Lake.geopotential height departure in mid-high latitude of East Asian had ’+-+’distribution.The western Pacific subtropical high had east-central position and weaker strength and the South China Sea subtropical high had south-central position and weaker strength.On the side,analysis showed that there was significant positive correlation between temperature in east Yunnan and SST in NINO4 region.Compared with 2008,although the impact of disasters in 2011 was shorter in time and smaller in area,but the frequent cold air process and a long stay of Kunming Quasi-stationary Front caused extreme low temperature and freeze disaster in east Yunnan in nearly 50 years.