ASY (Asymmetry Parameter) or asymmetry factor

Aerosol forcing (natural + anthropogenic)

Clear-sky aerosol forcing (natural + anthropogenic)

South Asian haze and monsoon rainfall inIndia and the Sahel

Chul Eddy Chung and V. Ramanathan

Center for Cloud, Chemistry and Climate (C4)Scripps Institution of OceanographyLa Jolla, California, USA

(published in 2006 J. Climate)

Anthropogenic Aerosol Radiative Forcingduring January-March(1996-1999)

Drying in India

Precipitation change

S. Asian haze effects

S. Asian haze effects

1951-2002observed trend

1951-2002observed trend

1985-2002observed trend

Greenhouse gas effects

Conclusions

1. Observations show that SSTs in the equatorial Indian Ocean have warmed by about 0.6 to 0.8 K since the 1950s, accompanied by very little warming or even a slight cooling trend over the northern Indian Ocean. The SST meridional gradient in N. Indian has been weakened in summer.

2. The weakening of the meridional SST gradient in N. Indian Ocean alone leads to a large decrease in Indian rainfall during summer months, ranging from 2 to 3 mm/day (CCM3 experiments). The SST weakening also enhances rainfall in sub-Saharan Africa.

3. The SST gradient change in this basin is likely due to anthropogenic aerosols in South Asia and the Indian Ocean.

4. The overall S. Asian haze effects (SST gradient change + aerosol radiative forcing) in CCM3 still produce drought in Indian and excess rainfall in Sahel.

5. It is thus implicated that the South Asian haze has mitigated the Sahel desiccation considerably.

S. Asian aerosols and Arabian cyclone

1Amato T. Evan, 2J. P Kossin, 3Chul Eddy Chung, 4V. Ramananathan 

1University of Virginia, Charlottesville VA2NOAA’s, National Climatic Data Center, Asheville, NC3Gwangju Institute of Science and Technology, Gwangju, South Korea4Scripps Institute of Oceanography, San Diego, CA

(To appear as a letter in Nature in November)

May-June cyclones

Genesis points (circles) and tracks (solid lines) are of pre-monsoon tropical cyclones during the period 1979–2010.

Strongest Arabian sea cyclones in the last 30 years.

Cyclone Name

Year LMI(m s-1)

Landfall Location

Loss of life

Total Affected

Damages(Million

2011 USD)

03A 1998 54 Gujarat India 2871 2871 643

02A 1999 57Karachi Pakistan 682 576,636 42

01A 2001 57 Gujarat India None None None

Gonu 2007 75Muscat Oman & Ras Al Kuh Iran 88 180,009 4203

Phet 2010 64Muscat Oman

&Karachi Pakistan

39 4000 1845

Distributions of pre- and post-monsoon LMI and storm-ambient vertical wind shear

30-year trends inpre-monsoon SST and vertical wind shear