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