热带气象学报2013，Vol.29Issue(3)：489-496,8.DOI:10.3969/j.issn.1004-4965.2013.03.016
前期季节内振荡对云南5月降水的影响
THE INFLUENCE OF PRECEDING INTRASEASONAL OSCILLATION ON THE PRECIPITATION IN MAY OVER YUNNAN
摘要
Abstract
Using OLR and wind reanalysis data and precipitation data,this paper discovers a key area (77.5～82.5 °E,5～10 °N) that shows significant correlation with Yunnan precipitation in May.LF (Low Frequency) OLR in the key area (Ikey) during pentads 2-3 of April (Ikey-Apr) shows significant negative correlation with the Yunnan precipitation in May.Ikey-Apr is negative in years of excessive May rain in Yunnan but positive in drought years.In years of excessive rain,strong LF convection in the key area in these pentads of April marks the establishment of the tropical Asian Monsoon (AM) in the key area and ISO (Intra-Seasonal Oscillation) entering the active phase.About 20 days later,this LF convection enters the active phase again.From the end of April to the beginning of May,the Southwest Monsoon is excited to propagate along the southwest-northeast direction and transport water vapor to Yunnan.When the LF convection arrives in Ynnnan and the Summer Monsoon establishes in Yunnan,its rainy season starts earlier and precipitation increases in May.However,when the LF signal in the key area appears at the end of April and the beginning of May,the second LF convection and the northeastward propagation of Southwest Monsoon ISO are also delayed,and the Summer Monsoon establishes in Yunnan and its rainy season begins at a later date,with decreased precipitation in May.Therefore,Ikey-Apr is precedent that signals whether the Yunnan rainy season will start early or late and whether its precipitation will be more or less.During the 4th pentad of April through the 5th pentad of May in years of excessive rain,ISO in Yunnan forms a complete wave.Before the 1st pentad of May,BOB (the Bay of Bengal) and Yunnan are controlled by repressed LF convection,and southwest water vapor transportation has not formed yet.From the 1st pentad of May,the LF convection in the key area moves northeastward,LF southwest wind in BOB strengthens,and warm and wet currents propagate to Yunnan.As a result,the Southwest Monsoon establishes in Yunnan where the rainy season starts early and precipitation increases quickly.关键词
季节内振荡/云南5月降水/低频OLR/孟加拉湾西南季风Key words
ISO/ Yunnan precipitation in May/ low frequency OLR/ Southwest Monsoon of Bay of Bengal分类
天文与地球科学引用本文复制引用
李汀,严欣,琚建华..前期季节内振荡对云南5月降水的影响[J].热带气象学报,2013,29(3):489-496,8.基金项目
国家公益性行业(气象)专项(GYHY201306022) （气象）
灾害天气国家重点实验室开放课题(2012LASW-A02)共同资助 （2012LASW-A02）
