Aerosols heat up

Aerosols are thought to have a cooling effect on the atmosphere, and therefore to have mitigated some of the expected global warming over this period. This is, however, a highly uncertain conclusion, in part because the total amount and vertical distribution of solar radiation that is absorbed by aerosol particles is imperfectly known. There was an interesting article in Nature (Vol-448, 2 August 2007) under “News and Views” by Prof. Peter Pilewskie. In the same issue, Ramanathan et al. (on page 575) report that the aerosol clouds above large regions of Asia actually cause as much warming as greenhouse gases — in contradiction, at first glance, to the notion of aerosol particles as a cooling agent.



Figure 1. Smog drifts down India's populous Ganges valley and out into the Bay of Bengal. This is the source of 'atmospheric brown clouds' over the Indian Ocean, and the climatic effect of its constituent aerosol particles is investigated by Ramanathan and colleagues




For more information and understanding, please refer following two articles and references therein:

Pilewskie, P., 2007, Aerosols heat up, Nature 448, 541-542.

Ramanathan et al. 2007, Warming trends in Asia amplified by brown cloud solar absorption, Nature 448, 575-578.

Aerosol Optical Thickness: MODIS Improved Product over Land

MODIS aerosol optical thickness (AOT) retrieval algorithm over land is continuously improving and now operational to produce collection 5 aerosol data products. Both Terra and Aqua data has been reprocessed using new retrieval algorithm. Click here to view current data processing status. New algorithm replaced the surface reflectance assumptions, the set of aerosol model optical properties, and the aerosol lookup table to reduce uncertainty in the product. In collection 5 retrievals of small-magnitude negative AOT values (down to −0.05) are considered valid, thus balancing the long term statistics of τ in near zero AOT conditions. Initial validation exercise conducted on this algorithm shows much improved retrievals of AOT. As consequence, global mean AOT for the test bed is reduced from ∼0.28 to ∼0.21.

Last month two research articles published in JGR-Atmosphere discussing new algorithm:

Levy R. C., L. A. Remer, S. Mattoo, E. F. Vermote, Y. J. Kaufman (2007), Second-generation operational algorithm: Retrieval of aerosol properties over land from inversion of Moderate Resolution Imaging Spectroradiometer spectral reflectance, J. Geophys. Res., 112, D13211, doi:10.1029/2006JD007811.

Levy R. C., L. A. Remer, O. Dubovik (2007), Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land, J. Geophys. Res., 112, D13210, doi:10.1029/2006JD007815.

International Symposium on Aerosol Chemistry Climate Interactions

My alma mater Physical Research Laboratory, Ahmedabad, India is holding an International Symposium on Aerosol-Chemistry-Climate Interactions

Symposium will be from 20-22 November 2007. Last date to send abstract is 31 August 2007.

The topics covered are

1. Observations of Atmospheric Parameters
Measurements of trace gases, aerosols, using in situ and remote sensing techniques

2. Transport and Transformation of Trace Gases and Aerosols
Long range and inter-continental transport, and stratosphere-troposphere exchange

3. Modeling of Atmospheric Processes
Emission inventories, sinks, model development and evaluation

4. Radiative Forcing and Climate Change
Aerosol-cloud interactions, impact on environment and climate

5. Space Instrumentation for Probing the Lower Atmosphere
Advances and developments in space techniques, sensor characterization and retrieval algorithms

Limited traveling and registration fee support will be provided to young scientists (below 35 years). For more information refer to conference web-page at http://www.prl.res.in/~acclint2007