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11
Impact of Air Pollution on Impact of Air Pollution on the South Asian the South Asian
MonsoonMonsoon
A Paper ReviewA Paper Review
Siv BalachandranSiv Balachandran
04/26/0704/26/07
22
OverviewOverview
MotivationMotivation South Asian MonsoonSouth Asian Monsoon Aerosols/Haze in South AsiaAerosols/Haze in South Asia Impact of Air Pollution on MonsoonImpact of Air Pollution on Monsoon
UNEP 2002UNEP 2002 Ramanathan et al 2005Ramanathan et al 2005 Chung et al 2006Chung et al 2006
ConclusionsConclusions
33
MODIS Satellite picture from wikepeMODIS Satellite picture from wikepediadia
44
UNEP 2002UNEP 2002 55
MotivationMotivation
IndiaIndia 1 Billion and growing1 Billion and growing Emissions are increasingEmissions are increasing
South AsiaSouth Asia Also growingAlso growing Monsoon = survivalMonsoon = survival Health ImpactsHealth Impacts
GloballyGlobally Transport of pollutionTransport of pollution Climate Change ImpactsClimate Change Impacts
66
The South Asian MonsoonThe South Asian Monsoon
2 monsoons2 monsoons June - September: SWJune - September: SW December - April: NEDecember - April: NE SW monsoon predominant SW monsoon predominant
for most of South Asiafor most of South Asia 1856 - 19971856 - 1997
30 El Nino, with 10 drought30 El Nino, with 10 drought 16 La Nina, with 7 flood16 La Nina, with 7 flood Studies suggest weakening Studies suggest weakening
due to global warmingdue to global warming
Anthropogenic aerosol Anthropogenic aerosol loadload
October to JuneOctober to June Peaks in Feb/MarchPeaks in Feb/March
May is transition periodMay is transition period Winds change from NE to Winds change from NE to
SWSW
April/May - warmestApril/May - warmest
UNEP 2002UNEP 2002 77
UNEP 2002UNEP 2002 88
Aerosol/Haze CompositionAerosol/Haze Composition
Natural vs. Natural vs. AnthropogenicAnthropogenic
INDOEXINDOEX Brown Cloud in dry Brown Cloud in dry
winter months due to winter months due to aerosolsaerosols
Monsoons wash out Monsoons wash out aerosolsaerosols
Carrico 2003Carrico 2003 99
Aerosol CompositionAerosol Composition
UNEP 2002UNEP 2002 1010
Ramanathan et al 2005Ramanathan et al 2005 1111
8 major impacts8 major impacts
Aerosol forcingAerosol forcing DimmingDimming Reduction in surface evaporationReduction in surface evaporation Surface coolingSurface cooling Weakening of latitudinal SST GradientsWeakening of latitudinal SST Gradients Stabilization of the troposphereStabilization of the troposphere Decrease in monsoon rainfallDecrease in monsoon rainfall ABC induced droughtsABC induced droughts
1212
Aerosol Impact on ClimateAerosol Impact on Climate
Direct EffectsDirect Effects Changes to Radiative ForcingChanges to Radiative Forcing
Indirect EffectsIndirect Effects Cloud albedoCloud albedo Cloud lifetimeCloud lifetime
Semi-DirectSemi-Direct Reduction in cloud cover and albedo due to Reduction in cloud cover and albedo due to
aerosol induced increase in solar heatingaerosol induced increase in solar heating
1313
Papers ReviewedPapers Reviewed
Ramanathan et al 2005Ramanathan et al 2005 Coupled ocean - atmospheric GCMCoupled ocean - atmospheric GCM CasesCases
• GHGs+SO4_2050 (business as usual)GHGs+SO4_2050 (business as usual)• ABC_1998 (GHGs, SO4, ABC @1998)ABC_1998 (GHGs, SO4, ABC @1998)• ABC_2050 (increases in GHGs and SO4 and ABC_2050 (increases in GHGs and SO4 and
extrapolates ABC forcing)extrapolates ABC forcing)• ABC_2050_1 (GHGs and SO4 held at 1998)ABC_2050_1 (GHGs and SO4 held at 1998)
Chung et al 2006Chung et al 2006 CCM3CCM3
Ramanathan et al 2005Ramanathan et al 2005 1414
Aerosol ForcingAerosol Forcing
UNEP 2002UNEP 2002 1515
Radiative Forcing ImpactsRadiative Forcing Impacts
Ramanathan et al 2005Ramanathan et al 2005 1616
DimmingDimming
1717
Impact of SST ChangesImpact of SST Changes
Atmospheric heating Atmospheric heating Surface Cooling Surface Cooling Indian Ocean SST changesIndian Ocean SST changes
NIO coolsNIO cools Equatorial IO warmsEquatorial IO warms
SST gradient affects pressure gradientSST gradient affects pressure gradient Pressure gradient affects circulationPressure gradient affects circulation Net effect = monsoon is disturbedNet effect = monsoon is disturbed
1818
Stabilization of the TroposphereStabilization of the Troposphere
In the first 5km: dT/dz = -5 to -6 K/kmIn the first 5km: dT/dz = -5 to -6 K/km Unstable to moist convectionUnstable to moist convection Instability coupled with low-level moisture Instability coupled with low-level moisture
convergence convergence deep convection deep convection Aerosols/haze confined to ~ 4kmAerosols/haze confined to ~ 4km
Heating of aerosol-loaded inhibits instability Heating of aerosol-loaded inhibits instability via differential warming of the atmospherevia differential warming of the atmosphere
1919
Pressure GradientsPressure Gradients Surface pressure late spring/early summerSurface pressure late spring/early summer
NIO is warmerNIO is warmer SOE > 1015 mbSOE > 1015 mb NIO < 1005 mbNIO < 1005 mb
Cross equatorial pressure gradient drives Cross equatorial pressure gradient drives moisture from SIO to South Asiamoisture from SIO to South Asia
Cooling of NIO causes SST gradient that Cooling of NIO causes SST gradient that reverses pressure gradientreverses pressure gradient
Mid to upper troposphere Mid to upper troposphere Cooler NIO Cooler NIO less deep convection in NIO less deep convection in NIO N to S circulation is disruptedN to S circulation is disrupted
Ramanathan et al 2005Ramanathan et al 2005 2020
Circulation ImpactsCirculation Impacts
Ramanathan et al 2005Ramanathan et al 2005 2121
Rainfall TrendsRainfall Trends
Chung et al 2006Chung et al 2006 2222
Chung et al 2006Chung et al 2006 2323
Ramanathan et al 2005Ramanathan et al 2005 2424
Increased DroughtsIncreased Droughts
2525
ConclusionsConclusions
Aerosol/haze impactsAerosol/haze impacts Direct and indirect effectsDirect and indirect effects SST changes affect circulationSST changes affect circulation DroughtsDroughts Transport of pollutionTransport of pollution
More than 1 billion people directly More than 1 billion people directly dependent on South Asian monsoondependent on South Asian monsoon Impacts to agriculture/health/globalImpacts to agriculture/health/global