简介:Inthisarticle,anewdefinitionfortheNorthHuaiheRiverrainyseason(NHRS)ispresentedusingsummerdailyprecipitationinEastChinaandsubtropicalhighridgeaxisat500hPa.BycalculatingtheannualprecipitationamountsintheNHRSandMeiyuoftheYangtze-HuaiheRiversbasin(YHMY)from1961to2009,thedatesofprecipitationbeginningandendingaswellasthedurationofthetworainyseasonsinthe49yearsareanalyzed.AtmosphericcirculationcharacteristicsinpositiveandnegativeprecipitationanomalyyearsduringtheNHRSarealsostudied.Resultsareshownasfollows.(1)ThenewdefinitionfortheNHRSismucheasiertouse.Itinvolvesonlytwometeorologicalfactors,makingitsapplicationmorepractical.ItcanalsodistinguishtworainyperiodsoftheNHRSmoreobjectively.(2)TheaveragedurationoftheNHRSissimilartothatoftheYHMY,exceptthatitsaveragedatesofbeginningandendingareaboutoneweeklaterthanthoseoftheYHMY.TheaverageprecipitationoftheNHRSisslightlylessthanthatoftheYHMY,andtheyearlyprecipitationvariationofthetworainyseasonsaresimilartoeachotherwithnoobviousincreasingordecreasingtrendinthe49years,butwithdistinguisheddecadalandinter-annualvariations.(3)Inpositiveprecipitationanomalyyears,theSouthAsianhighmovesmorenorthwardandmoreeastward,thewesternPacificsubtropicalhighislocatedmorenorthwardandwestward,andthesummermonsoonisstrongerthannormal,resultingintheconvergenceofthewarmandmoistsouthwesterlyairflowfromthewestsideofthesubtropicalhighandthecoldairfromthenorthsideofthenortheasttroughinNorthHuaiheRiverbasin.