简介:Byusingtheupper-winddatafromJuly1980toJune1983,thevariationsofthelow-frequencyoscillation(LFO)intheatmospherebeforeandduring1982ElNinohavebeeninvestigated.BeforetheElNino,theLFOpropagatesfromwesttoeastovertheequatoroftheEasternHemisphereandfromeasttowestover20°N.TheeastwardpropagatingLFOovertheequatorconsistsofzonalwavenumber1propagatingeastwardandzonalwavenumber2withacharacterofstationarywave.Theoscillationofzonalwavenumber2canmodulatetheoscillationstrength.AftertheonsetoftheElNino,thepropagatingdirectionsoftheLFOovertheequatorand20°NoftheEasternHemispherechangetobewestwardandeastward,respectively.TheLFOoverthewesternPacificweakensrapidlyandonecomingfrommiddleandhighlatitudespropagatestotheequator.Fromthephasecompositionsofstreamlinefieldsforthezonalwavenumber1ofequatorialwestwardpropa-gatirgLFO,itisfoundthattheatmosphericheatsourceintheequatoroftheeasternPacific(EEP)excitesaseriesoftheequatorialcyclonesandanticycloneswhichmovenorthwardandwestwardandformthewestwardpropagatingLFOovertheequator.Withthewavelengthof20000km,thiskindofequatorialwaveissimilartothemixingRossby-gravitywave.Initswestwardandnorthwardmovement,thecirculationinEastAsiaismodified.ThismaybethemechanismoftheinfluenceofElNinoontheclimateofChina.
简介:Abaroclinicsemi-geostrophicmodelwithevaporation-windfeedbackmechanism(EWFM)andCISKisestablished,twonon-dimensionalparametersaandηareintroducedtorepresentEWFMandCISK,respectively.Analyticsolutionsofthemodelsystemareobtained,dynamicsanalysesandthemodelatmospherecalculationsfurtherconfirmthatEWFMandCISKareveryimportantphysicalprocessesinleadingtothelow-frequencyoscillationsinthetropics.
简介:BasedontheNCEP/NCARreanalysisdataandtheobservedprecipitationdatainthesouthofChinafrom1958to2000,theimpactof30to60dayoscillationofatmosphericheatsourcesonthedroughtandfloodeventsinJuneinthesouthofChinaisdiscussed.Duringtheflood(drought)events,thereexistsananomalouslow-frequencyanticyclone(cyclone)atthelowlevelofthetroposphereovertheSouthChinaSeaandthenorthwesternPacific,accompaniedwithanomalouslow-frequencyheatsinks(heatsources),whilethereexistsananomalouslow-frequencycyclone(anticyclone)withanomalousheatsources(sinks)overtheareafromthesouthofChinatothesouthofJapan.Onaverage,thephaseevolutionofthelow-frequencyindroughteventsis7to11daysaheadofthatinfloodeventsinMaytoJuneinthesouthofChina.Infloodevents,low-frequencyheatsourcesandcyclonesarepropagatednorthwardfromthesouthernSouthChinaSea,northwestwardfromthewarmpoolofthewesternPacificandwestwardfromthenorthwesternPacificaround140°E,whichhaveveryimportantimpactontheabundantrainfallinJuneinthesouthofChina.However,indroughtevents,thenorthwardpropagationsofthelow-frequencyheatsourcesandcyclonesfromtheSouthChinaSeaanditsvicinityareratherlatecomparedwiththoseinfloodevents,andthereisnoobviouswestwardpropagationoftheheatsourcesfromthenorthwesternPacific.Thetimingofthelow-frequencyheatsourcepropagationhasremarkableimpactontheJunerainfallinthesouthofChina.
简介:热带降雨测量的影响结构和intraseasonal摆动(ISO)的内在的物理上的使命(TRMM)降水产品与美国国家航空学和观察系统模型版本3的空格管理戈达德土(GEOS-3)被调查数据吸收系统(DAS)。在1998夏天的强壮的ISO阶段显然位于亚洲季风区域和东方赤道的和平的区域。当向东北的繁殖是在30点的突出的ISO到超过10的60天的摆动时,东方繁殖是为在20点的热带ISO的一个主导的特征到30天的摆动
简介:研究海洋的波候变化是了解海洋动力过程对气候变迁响应的关键。渤海所处特殊的地理位置,使其波候在长期风场变化影响下存在阶段性变化特征。文章采用1950~2011年NCEP再分析资料中的渤海海域10m风场资料,利用SWAN模式模拟逐月渤海波浪的有效波高、波向、波周期,分析该海区波候的变化特征。分析结果显示:1950~2011年期间渤海海域的有效波高呈现下降的趋势;波向角度均呈现上升的趋势,波周期相对平稳,略有上升;有效波高平均下降0.3cm/a,波向角度平均增加0.12°/a。有效波高在1968年前后显现突变点,波向角度约在1960年突变,波周期在1965年左右出现突变点。渤海波候变化与海气振荡密切相关,是大尺度的大气环流变异导致的结果,长期气候变化背景下,东亚环流天气系统的长期变化(包括东亚季风强度、夏季风北界的移动,西太平洋副热带高压面积与强度的变化、脊点位置西伸与北进,以及西风指数的强弱变化等),是影响和控制渤海海域波气长期变化的主要原因。