TPE-GHP/GEWEX Joint Workshop Long-term Changes in South Asian Monsoon · 2017. 10. 24. · • The...
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TPE-GHP/GEWEX Joint Workshop Hotel Himalaya, Lalitpur Nepal 17-19 October 2017 Long-term Changes in South Asian Monsoon Madan Lall Shrestha Academician Nepal Academy of Science and technology
Transcript of TPE-GHP/GEWEX Joint Workshop Long-term Changes in South Asian Monsoon · 2017. 10. 24. · • The...
TPE-GHP/GEWEXJointWorkshop
HotelHimalaya,LalitpurNepal
17-19October2017
Long-termChangesinSouthAsianMonsoon
MadanLallShresthaAcademician
NepalAcademyofScienceandtechnology
Schema<cdiagramofborealwinter(December-February;leF)andsummer(June-August;right)dailymeanprecipita<on,seasurface
temperature(SST)andwinds.
Turner,A.G.andH.Annamalai(2012)
(Source:IITM)
EpochalPaEernsofAll-IndiaSummerMonsoonRainfall
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All Nepal monsoon rainfall anomaly
RCP2.6 RCP8.5
Source:IPCC2014
Observed(thickcontour)andsimulated(shading)globalmonsoondomain(Wangetal,2011).[26CMIP5mul<-modelmeanprecipita<oninthepresentday(1986–2005)andthefuture(2080–2099;RCP8.5scenario)].
ClimatemodelsandGlobalMonsoon
• Thereisgrowingevidenceofimprovedskillofclimatemodelsinreproducingclimatologicalfeaturesoftheglobalmonsoon.
• Theglobalmonsoon,aggregatedoverallmonsoonsystems,islikelytostrengtheninthe21stcenturywithincreasesinitsareaandintensity,whilethemonsooncirculaOonweakens.
• Monsoononsetdatesarelikelytobecomeearlierornottochangemuchandmonsoonretreatdatesarelikelytodelay,resulOnginlengtheningofthemonsoonseasoninmanyregions.
Regional:SouthAsianMonsoon
• Modelskillinrepresen<ngregionalmonsoonsislowercomparedtotheglobalmonsoonandvariesacrossdifferentmonsoonsystems.
• ThereismediumconfidencethattheIndiansummermonsooncircula<onwillweaken,butthisiscompensatedbyincreasedatmosphericmoisturecontent,leadingtomoreprecipita<on.
• Therealismoftherepresenta<onofElNiño-SouthernOscilla<on(ENSO)inclimatemodelsisincreasingandmodelssimulateongoingENSOvariabilityinthefuture.ThereforethereishighconfidencethatENSOverylikelyremainsasthedominantmodeofinterannualvariabilityinthefutureandduetoincreasedmoistureavailability,theassociatedprecipita<onvariabilityonregionalscaleslikelyintensifies.
IPCC2014
• Thereislowconfidenceinprojec<onsoffuturechangesintheMadden–JulianOscilla<onowingtopoorabilityofthemodelstosimulateitanditssensi<vitytooceanwarmingpa`erns.
Time series of summermonsoon index rela<ve to thebaseperiod average(1986–2005)over SouthAsia (definedasmeridionaldifferencesof the JJA850hPa zonalwindsaveragedover5°N to15°N,40°E to80°Eand20°N to30°N,60°Eto90°E)
IPCC2014RCP4.5lightblueRCP8.5red
StrengthofMonsooncirculaOon
Changesinprecipita<onindicesovertheregionallandmonsoondomainsofSouthernAsia Time series of observed andmodel-simulated summer precipita<on anomalies(%)rela<vetothepresent-dayaverage
IPCC2014
RCP2.6-darkblue(24)RCP4.5–lightblue(34)RCP6.0–orange(20)RCP8.5–red(32)
• TheSouthAsianmonsoonisremarkablystableasawholewithinterannualvaria<onofonlyaround10%inmostcasesandinfluencevarioussectorslikeagriculturalproduc<onandthestocksandcommodi<esmarket,soa5-10%changeontopcouldhavesignificantimpacts.(Turner2012)
• Thefloodanddroughtsarecommonphenomenaandtendencytobemorefrequent.
• In2002forexampleinIndia,abreakinthemonsoon
rainssawJulyreceivingonlyabout50%ofitsnormalrainfall,leadingtocutsinagriculturaloutputanddecliningGDP.Thinkingaboutclimatechangeinthecontextofhowtheseextremeeventswillchangecanhelpfarmersandotherenduserstounderstanditsimplica<ons.
Monsoonmeanprecipita<on,andcompositeanomaliesfor(b)ac<veand(c)breakphasesinAPHRODITE.Unit:mmday−1(Karmacharyaetal,2017)
IntraseasonalchangesinSouthAsianMonsoon
RCM50
RCM12
(Karmacharyaetal,2017)
Lowerlevel(850hPa)monsoonmeancircula<on(windvector)andver<calcomponentofrela<vevor<city(shaded),andcompositeanomaliesfor(b)ac<veand(c)breakphasesinERAI.(Karmacharyaetal,2017)
RCM12
Laggedmonsoontroughposi<onat850hpafor(a)ac<veand(b)breakcompositesinERAI.
RCM12
Conclusion• Therearelargeinterannualvaria<oninlong-term
precipita<onrecordoverSouthAsia.Significantcorrela<onwithENSO.
• Thoughthemonsooncircula<onisgenngweaker,thereisanstrongindica<onthattheprecipita<onisgoingtoincrease.
• Modelhavebeenabletocapturetheintraseasonalchangescharacteris<cs.
• ThegriddeddatasuchasAPHRODITEdatasetsareuseful.However,thereisalsoaneedtovalidateanddevelopabe`erone.
• Therearediscrepanciesinresolu<onofthesamesetofdatawithintheregion,whichneedstoovercometouseeffec<velyintheresearch.
Conclusion(contd.)• Thereisalwaysahugetasktofillupthedatasparseregion.
Needtoestablishadequatesta<onsinthemountainousregion(Himalayanregion),whicharenecessaryinvalida<ngthemodelresults.Needtoexploremechanismtohaveagoodsta<onnetwork.
• Needforaconsolidatedinforma<on(data)plaoormforfurtherresearchac<vi<esintheregion.
