简介:ElNioorLaNiamanifestinDecemberoverthePacificandwillserveasanindexfortheforecastingofsubsequentIndiansummermonsoon,whichoccursfromJunetomid-September.Inthepresentarticle,anattemptismadetostudythevariationoflatentheatflux(LHF)overthenorthIndianOceanduringstrongElNioandstrongLaNiaandrelateitwithIndianmonsoonrainfall.DuringstrongElNiotheLHFintensityishigherandassociatedwithhigherwindspeedandlowercloudamount.DuringElNioallIndiarainfallishavinganinverserelationwithLHF.SeasonalrainfallishigherinYY+1(subsequentyear)thanYY(yearofoccurrence).HoweverthereisalaginrainfallduringElNioYY+1fromJunetoJulywhencomparedwiththemonthlyrainfall.
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简介:BasedonGlobalOceanDataAssimilationSystem(GODAS)andNCEPreanalysisdata,atmosphericandoceanicprocessespossiblyresponsiblefortheonsetofthe2011/12LaNiaevent,whichfollowedthe2010/11LaNiaeven—referredtoasa'doubledip'LaNia—areinvestigated.Thekeymechanismsinvolvedinactivatingthe2011/12LaNiaareillustratedbythesedatasets.ResultsshowthatneutralconditionswerealreadyevidentintheequatorialeasternPacificduringthedecayingphaseofthe2010/11LaNia.However,isothermalanalysesshowobviouslycoldwaterstillpersistingatthesurfaceandatsubsurfacedepthsinoff-equatorialregionsthroughoutearly2011,beingmostpronouncedinthetropicalSouthPacific.ThenegativeSSTanomaliesinthetropicalSouthPacificactedtostrengthenasouthernwindacrosstheequator.ThesubsurfacecoldwaterinthetropicalSouthPacificthenspreadnorthwardandbrokeintotheequatorialregionatthethermoclinedepth.Thisincursionprocessofoff-equatorialsubsurfacecoldwatersuccessfullyinterruptedtheeasternpropagationofwarmwateralongtheequator,whichhadpreviouslyaccumulatedatsubsurfacedepthsinthewarmpoolduringthe2010/11LaNiaevent.Furthermore,theincursionprocessstrengthenedasaresultoftheoff-equatorialeffects,mostlyinthetropicalSouthPacific.ThenegativeSSTanomaliesthenreappearedinthecentralbasininsummer2011,andactedtotriggerlocalcoupledair–seainteractionstoproduceatmospheric–oceanicanomaliesthatdevelopedandevolvedwiththesecondcoolinginthefallof2011.