低频振荡对2015年春季云南东部降水异常的影响  

Influence of Low-Frequency Oscillation on Abnormal Precipitation over Eastern Yunnan Province in Spring 2015

作　　者：陈艳[1,2] 张万诚 陶云[1,2] 任菊章 段长春[1] CHEN Yan;ZHANG Wancheng;TAO Yun;REN Juzhang;DUAN Changchun(Yunnan Institute of Meteorological Sciences,Kunming 650034;Research Centre for Disastrous Weather in Hengduan Mountain and Low-Latitude Plateau,CMA,Kunming 650034)

机构地区：[1]云南省气象科学研究所,昆明650034 [2]中国气象局横断山区(低纬高原)灾害性天气研究中心,昆明650034

出　　处：《气象》2021年第7期805-816,共12页Meteorological Monthly

基　　金：中国科学院战略性先导科技专项(XDA20100304);国家自然科学基金项目(41790471、41965005、42075013);中国气象局省级科研所科技创新发展项目(SSFZ201821)共同资助。

摘　　要：以往的研究显示,厄尔尼诺是导致云南春季干旱的重要原因。2015年,在超强厄尔尼诺事件背景下,滇西大部春季降水偏少,雨季开始偏晚至特晚;然而,东部地区降水总体偏多,部分区域雨季开始偏早至特早,东西部形成了鲜明对比。利用云南省逐日观测降水、全球测站均一化逐日格点降水和NCEP/NCAR再分析资料,运用统计和动力诊断方法,研究了2015年春季10~30 d大气低频振荡特征及其对云南东部降水异常的影响。分析显示,3月中旬至4月下旬,100°E以东地区10~30 d大气低频振荡异常活跃,是造成云南东部地区降水偏多的重要原因。在低频振荡影响下,云南东部先后出现了3次明显的降水过程,每一次过程都与欧亚型低频波列上低频冷位相的南压密切相关。即当低频冷位相向南移动时,东亚副热带西风急流随之南压,当其入口区次级环流上升支移至云南上空,并与南下冷高压西南侧有利的回流水汽相互作用时即形成了降水。Previous literatures suggest that El Nino is a dominant factor causing spring drought in Yunnan Province.Under the background of super-strong El Nino event during 2015,the spring(March-May)precipitation in most parts of western Yunnan Province was below normal,and the rainy season started late or even very late.However,the precipitation in eastern part was more than normal generally,and the rainy seasons in some regions started early or even very early,presenting a sharp contrast between the east and west.By using daily rain gauge precipitation of Yunnan Province,the CPC(Climate Prediction Center,USA)global unified gauge-based analysis of daily precipitation and NCEP/NCAR(National Centers for Environmental Prediction/National Center for Atmospheric Research)reanalysis data,the influence of 10-30 d atmospheric oscillation on the spring abnormal precipitation over eastern Yunnan was studied by statistical and dynamical diagnosis methods.The analysis shows that the 10-30 d oscillation was active in the areas to the east of 100°E from mid-March to late-April,which is a major reason for the abnormalabundantprecipitation over eastern Yunnan.Three distinct precipitation processes in eastern Yunnan happened associated closely with the southward approaching of the low-frequency cold phase embedded in the Eurasian pattern(EU)wave train from the mid-and high-latitudes of East Asia.Namely,when the upward branch of the secondary circulation around the subtropical westerly jet entrance interacted with the reflux vapor on the southwestern fringe of the cold high,the rainfall process was formed.

关 键 词：低频振荡 春季降水 雨季开始 云南 

分 类 号：P461[天文地球—大气科学及气象学]