1. 1 Impact of Air Pollution on the South Asian Monsoon A Paper Review Siv Balachandran 04/26/07

2. 2 Overview  Motivation  South Asian Monsoon  Aerosols/Haze in South Asia  Impact of Air Pollution on Monsoon UNEP 2002 UNEP 2002 Ramanathan et al 2005 Ramanathan et al 2005 Chung et al 2006 Chung et al 2006  Conclusions

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4. MODIS Satellite picture from wikepedia4

5. UNEP 20025 Motivation  India 1 Billion and growing 1 Billion and growing Emissions are increasing Emissions are increasing  South Asia Also growing Also growing Monsoon = survival Monsoon = survival Health Impacts Health Impacts  Globally Transport of pollution Transport of pollution Climate Change Impacts Climate Change Impacts

6. 6 The South Asian Monsoon  2 monsoons June - September: SW June - September: SW December - April: NE December - April: NE SW monsoon predominant for most of South Asia SW monsoon predominant for most of South Asia  1856 - 1997 30 El Nino, with 10 drought 30 El Nino, with 10 drought 16 La Nina, with 7 flood 16 La Nina, with 7 flood Studies suggest weakening due to global warming Studies suggest weakening due to global warming  Anthropogenic aerosol load October to June Peaks in Feb/March  May is transition period Winds change from NE to SW  April/May - warmest

7. UNEP 20027

8. 8 Aerosol/Haze Composition  Natural vs. Anthropogenic  INDOEX Brown Cloud in dry winter months due to aerosols Brown Cloud in dry winter months due to aerosols  Monsoons wash out aerosols

9. Carrico 20039 Aerosol Composition

10. UNEP 200210

11. Ramanathan et al 200511 8 major impacts  Aerosol forcing  Dimming  Reduction in surface evaporation  Surface cooling  Weakening of latitudinal SST Gradients  Stabilization of the troposphere  Decrease in monsoon rainfall  ABC induced droughts

12. 12 Aerosol Impact on Climate  Direct Effects Changes to Radiative Forcing Changes to Radiative Forcing  Indirect Effects Cloud albedo Cloud albedo Cloud lifetime Cloud lifetime  Semi-Direct Reduction in cloud cover and albedo due to aerosol induced increase in solar heating Reduction in cloud cover and albedo due to aerosol induced increase in solar heating

13. 13 Papers Reviewed  Ramanathan et al 2005 Coupled ocean - atmospheric GCM Coupled ocean - atmospheric GCM Cases Cases 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 extrapolates ABC forcing)ABC_2050 (increases in GHGs and SO4 and extrapolates ABC forcing) ABC_2050_1 (GHGs and SO4 held at 1998)ABC_2050_1 (GHGs and SO4 held at 1998)  Chung et al 2006 CCM3 CCM3

14. Ramanathan et al 200514 Aerosol Forcing

15. UNEP 200215 Radiative Forcing Impacts

16. Ramanathan et al 200516 Dimming

17. 17 Impact of SST Changes  Atmospheric heating  Surface Cooling  Indian Ocean SST changes NIO cools NIO cools Equatorial IO warms Equatorial IO warms  SST gradient affects pressure gradient  Pressure gradient affects circulation  Net effect = monsoon is disturbed

18. 18 Stabilization of the Troposphere  In the first 5km: dT/dz = -5 to -6 K/km  Unstable to moist convection  Instability coupled with low-level moisture convergence  deep convection  Aerosols/haze confined to ~ 4km Heating of aerosol-loaded inhibits instability via differential warming of the atmosphere Heating of aerosol-loaded inhibits instability via differential warming of the atmosphere

19. 19 Pressure Gradients  Surface pressure late spring/early summer NIO is warmer NIO is warmer SOE > 1015 mb SOE > 1015 mb NIO < 1005 mb NIO < 1005 mb  Cross equatorial pressure gradient drives moisture from SIO to South Asia  Cooling of NIO causes SST gradient that reverses pressure gradient  Mid to upper troposphere Cooler NIO  less deep convection in NIO Cooler NIO  less deep convection in NIO N to S circulation is disrupted N to S circulation is disrupted

20. Ramanathan et al 200520 Circulation Impacts

21. Ramanathan et al 200521 Rainfall Trends

22. Chung et al 200622

23. Chung et al 200623

24. Ramanathan et al 200524 Increased Droughts

25. 25 Conclusions  Aerosol/haze impacts Direct and indirect effects Direct and indirect effects SST changes affect circulation SST changes affect circulation Droughts Droughts Transport of pollution Transport of pollution  More than 1 billion people directly dependent on South Asian monsoon Impacts to agriculture/health/global Impacts to agriculture/health/global