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Warm Indian OceanWeak Asian MonsoonDuring the past century 1 Where has all the heat gone Land Atmosphere Ocean .2 Has this heat distribution changed themonsoon drivers 3 Is the South Asian Monsoon decreasing Orincreasing 4 Role of Indian Ocean warming .5 Aerosols anyone Roxy M K 1 K Ritika1 2 P Terray1 3 IPCC AR5R Murtugudde4 K Ashok1 5 and B N Goswami1 6Indian Institute of Tropical Meteorology PuneFergusson College Pune 3 Sorbonne Universites Paris France.University of Maryland Maryland USA 5 University of Hyderabad Indian Institute of Science Education and Research Pune Changes in Monsoon driversIncrease in land sea contrast in the NorthernHemisphere.Observations and climate models suggest an increase inland sea contrast over Northern Hemisphere during recent as surface temperatures over land increase more rapidlyObservatiosea in response to greenhouse gas forcing .Climate Model response to CO2 IPCC AR4 Ensemble Sutton et al GRL 2007 Hansen et al Rev Geophys 2010 Changes in Monsoon driversBasin wide Warm pool warming in recent.decades Studies note basin wide warming over Indian Ocean in the lastSuggested causes 1 Greenhouse warming Du and Xie 2014 2 Weakening winds causing warming trends Swapna et3 Ocean dynamics Warm SST triggers a local air sea.coupled interaction Rao et al 2012 Du et al 2009 Lau etal 2000 enlargement inSST trend during last 504 Oceanyearsdynamics Chowdary et al 2007 .Chambers et al JGR 1999 Alory et al GRL 2007 Rao et al ClimaticChange 2012 Changes in Monsoon driverswestern Indian Ocean warmed up to 1 2degC in 100 yrs SST trend June Sept C 112 year 1 .Significantwarming overwestern IndianSST anomalies C east Pacific vs WIO June Sept meanr 0 6 east Pacific.Linked to El Nino WIOevents 1 S D 0 77 C5 Asymmetry in ENSO a Climatological mean SST C 6 Skewness in ENSO a SST Skewness 1901 1950 . b El Ni o Composite SST anomalies C b SST Skewness 1951 2012 c La Ni a Composite SST anomalies C Ideally Increased land sea contrast moreIncreased land sea ocean warming more.Increased ocean rainfallenhances convectionPrecipitation mm day 20 21 22 23 24 25 26 27 28 29 30 31Increased SLP meridional gradient. 73 95E 15 30N 50 100E 25 40S JJASGadgil et al Nature 1984 Roxy Climate Dynamics 2013 but it s a Weak South Asian Monsooncentral India shows significant reduction in. a rainfallTrend in IMD Precip b Trend in CRU Precip 1 1mm day 112 year Decreasing trend inprecipitation from.Pakistan throughcentral India toBangladesh Significant overcentral Indian.subcontinent horse shoe pattern Similar results from subdivisionalstation data Guhathakurta and Rajeevan 2008.Guhathakurta and Rajeevan IJOC 2008Pai et al Climate Dynamics Warm Indian Ocean Weak South AsianIndian Ocean warming well correlated a Trend in IMD Precip with b Trend in CRU Precip . a b Rainfall Trendmm day 1 112 year 1 weak Precip Decreasing trend inprecipitation from Pakistanthrough central India to.Bangladesh Significantover central Indiansubcontinent c Correlation WIO HadISST vs IMD Precip d Correlation WIO ERSST vs CRU Precip c d Correlation.Trend and correlation withwestern Indian Oceanwarming has similar horse shoe pattern Roxy et al Nature Communications 2015 Revised. Land sea contrast over South Asian domainIndian Ocean large warming Subcontinent suppressedwarming C 112 year 1 a surface temperature trends b upper troposphere temp trends C 65 year 1 c Trend in land sea temperature difference.Though models and observations suggestincrease in land sea contrast over NorthernHemisphere due to global warming it isdifferent over South Asia Indian Ocean Ttrop C .Tsurf C The decrease in land sea contrast reflects intropospheric temperature gradients also TtropRoxy et al Nature Communications 2015 Revised Weakening local Hadley circulation Convection.enhanced over ocean and suppressed overObservations trend in vertical velocity 1948 2012 Trend in vertical wind velocity June Sept 1948 2012 Pa s 1 65 year 1 a surface temperature trends C 112 year 1 b upper troposphere temp trends C 65 year 1 .SST warming extends the warm pool andincreases ocean convectionCompensated by subsidence of airLarge scale upward motion over the Indianover the subcontinent 10 20N .ocean 10S 10N extending up to theinhibiting convection over theupper troposphere and favoring intenselandmass and drying the region local convection . Weakened Monsoon precip winds due toModel simulationssimulated with Indian Ocean warmingwarming of WIOSST difference between CFSv2 WIO and CFSv2 CTL Model simulated response to.Precip and Winds DIfference between CFSv2 and CFSv2 1 mm day 65 year 11 m s 1 65 year 1 Competition between ocean and land rainfall SST warming extends the warm pool and increases ocean. but results in decreased rainfall over the subcontinent horseshoe pattern in model simulations with increased IO Weakening local Hadley circulationModel simulations with Indian Ocean warmingObservations trend in vertical velocity. 1948 2012 Trend in vertical wind velocity June Sept 1948 2012 1 1Pa s 65 year Simulations change in verticalvelocity in response to Indian.Ocean warmingVertical wind velocity DIfference between CFSv2WIO and CFSv2CTL Pa s 1 Role of other monsoon drivers.aerosol cooling stratosphere tropospherelandinteractions surface aerosol upper troposphere stratospheric a surface temperature trends C 112 year 1 .interactions b upper troposphere temp trends C 65 year 1 Krishnan and Ramanathan GRL 2002Sanap et al Climate Dynamics 2015 Yu et al GRL 2004 Warm Indian Ocean.Weak Asian Monsoon Future SST trend June Sept C 112 year 1 CMIP5 future projections a Trend in IMD Precip b Trend in CRU Precip mm day 1 112 year 1 suggest further warming of theIndian Ocean Will the.monsoon decrease further These future simulations alsosuggest increasing monsoon Sharmila et al 2015 However it is to be noted that.these models fail to reproducethe present day monsoon Sabeerali et al 2014 Saha etThank You SLP meridional gradient 73E 95E 15N 30N 50E 100E .40S 25S JJASWhile the local circulation is weakening large scalecirculation is in fact strengthening Krishnan et al 2012 with non homogenous data c Homogenous data 1901 2004 . Same period as in a but homogenous dataPune. 2 Fergusson College, Pune 3 Sorbonne Universites, Paris, France. 4 University of Maryland, Maryland, USA 5 University of Hyderabad, Hyderabad. 6 Indian Institute of Science Education and Research, Pune. During the past centuryâ€¦ Where has all the heat gone â€“ Land/Atmosphere/Ocean? Has this heat distribution changed the monsoon drivers?