Biweekly Oscillation Of Apparent Heat Source Over Tibet Plateau And Its Intensity Annual Variation During Boreal Summer

Based on reanalysis data set provided by ECMWF,daily and monthly mean reanalysis data form NCEP/NCAR,and precipitation data from Chinese National Meteorological Information Center.This paper intends to reveal the characteristics of apparent heat source biweekly oscillation over Tibet Plateau and annual variation of its intensify.The main conclusions are as follows:(1)During summer time,daily apparent heat source over the Tibetan Plateau has better coherence at the first place,with its corresponding time coefficients showing notable inter-seasonal feature,this kind of feature changes from year to year.Each year 10-20 days biweekly oscillation exits significantly over Tibetan Plateau.(2)As phase evolving,there are two systems taking effects on biweekly oscillation over Tibet Plateau apparent heat source,one of them is the mid-high latitude system moving from north-east Asia to Tibet Plateau,another is the low latitude system moving from east of Philippines to Bay of Bengal.Interaction between these two systems may work out through subtropical meridional circulation.(3)In these paper,standardization of Tibet plateau area mean apparent heat source variation is used as index which can represent intensify variation of apparent heat source biweekly oscillation.During 1979-2015,this index shows up annual variation period.Besides,sea surface temperature changes in several sea basins can influence intensify of Tibet plateau apparent heat source biweekly oscillation,main influence factors are different during different year.The flowing year of ENSO,it is Pacific basin that plays the leading role,while the tropical pacific sea surface temperature is at its normal phase,the main factor turned out to be sea surface temperature anomaly over Atlantic.(4)There is a good correspondence between peak and valley of apparent heat source biweekly oscillation over Tibet plateau and precipitation in the middle and lower reaches of the Yangtze river during summer time.In biweekly oscillation active years,summer time mean precipitation exits no apparently anomaly,but inter-seasonal dry and wet phase changes frequently,that indicates drought and flood coexist likely to happen in eastern of China.