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2008 .

(5 publications)

S. Verma, C. Venkataraman, and O. Boucher. Origin of surface and columnar Indian Ocean Experiment (INDOEX) aerosols using source- and region-tagged emissions transport in a general circulation model. Journal of Geophysical Research (Atmospheres), 113:24211, December 2008. [ bib | DOI | ADS link ]

We study the relative influence of aerosols emitted from different sectors and geographical regions on aerosol loading in south Asia. Sectors contributing aerosol emissions include biofuel and fossil fuel combustion, open biomass burning, and natural sources. Geographical regions include India (the Indo-Gangetic plain, central India, south India, and northwest India), southeast Asia, east Asia, Africa-west Asia, and the rest of the world. Simulations of the Indian Ocean Experiment (INDOEX), from January to March 1999, are made in the general circulation model of Laboratoire de Météorologie Dynamique (LMD-ZT GCM) with emissions tagged by sector and geographical region. Anthropogenic emissions dominate (54-88%) the predicted aerosol optical depth (AOD) over all the receptor regions. Among the anthropogenic sectors, fossil fuel combustion has the largest overall influence on aerosol loading, primarily sulfate, with emissions from India (50-80%) and rest of the world significantly influencing surface concentrations and AOD. Biofuel combustion has a significant influence on both the surface and columnar black carbon (BC) in particular over the Indian subcontinent and Bay of Bengal with emissions largely from the Indian region (60-80%). Open biomass burning emissions influence organic matter (OM) significantly, and arise largely from Africa-west Asia. The emissions from Africa-west Asia affect the carbonaceous aerosols AOD in all receptor regions, with their largest influence (AOD-BC: 60%; and AOD-OM: 70%) over the Arabian Sea. Among Indian regions, the Indo-Gangetic Plain is the largest contributor to anthropogenic surface mass concentrations and AOD over the Bay of Bengal and India. Dust aerosols are contributed mainly through the long-range transport from Africa-west Asia over the receptor regions. Overall, the model estimates significant intercontinental incursion of aerosol, for example, BC, OM, and dust from Africa-west Asia and sulfate from distant regions (rest of the world) into the INDOEX domain.

J.-J. Morcrette, A. Beljaars, A. Benedetti, L. Jones, and O. Boucher. Sea-salt and dust aerosols in the ECMWF IFS model. Geophysical Research Letters, 35:24813, December 2008. [ bib | DOI | ADS link ]

The ECMWF IFS model has recently been modified to include prognostic aerosols in its analysis and forecast modules. For the sea salt and dust components, comparisons of three versions of the model are presented: (i) a forecast only model started from conventional analysis with free-running aerosols, (ii) a full analysis including aerosols, and (iii) as in (i) but with sea salt and dust sources revised to account for the 10-m wind including gustiness and calibrated on the aerosol analysis results. It is shown that this new formulation of the sources of the main natural aerosols gives an improved agreement with AERONET surface observations where sea salt and dust aerosols are dominant. It also shows how the information brought by the aerosol analysis can be used to improve the representation of aerosols in numerical weather prediction and climate-type general circulation models.

J. Quaas, O. Boucher, N. Bellouin, and S. Kinne. Satellite-based estimate of the direct and indirect aerosol climate forcing. Journal of Geophysical Research (Atmospheres), 113:5204, March 2008. [ bib | DOI | ADS link ]

The main uncertainty in anthropogenic forcing of the Earth's climate stems from pollution aerosols, particularly their “indirect effect” whereby aerosols modify cloud properties. We develop a new methodology to derive a measurement-based estimate using almost exclusively information from an Earth radiation budget instrument (CERES) and a radiometer (MODIS). We derive a statistical relationship between planetary albedo and cloud properties, and, further, between the cloud properties and column aerosol concentration. Combining these relationships with a data set of satellite-derived anthropogenic aerosol fraction, we estimate an anthropogenic radiative forcing of -0.9 +/- 0.4 Wm-2 for the aerosol direct effect and of -0.2 +/- 0.1 Wm-2 for the cloud albedo effect. Because of uncertainties in both satellite data and the method, the uncertainty of this result is likely larger than the values given here which correspond only to the quantifiable error estimates. The results nevertheless indicate that current global climate models may overestimate the cloud albedo effect.

A. Hollingsworth, R. J. Engelen, C. Textor, A. Benedetti, O. Boucher, F. Chevallier, A. Dethof, H. Elbern, H. Eskes, J. Flemming, C. Granier, J. W. Kaiser, J.-J. Morcrette, P. Rayner, V.-H. Peuch, L. Rouil, M. G. Schultz, and A. J. Simmons. Toward a Monitoring and Forecasting System For Atmospheric Composition: The GEMS Project. Bulletin of the American Meteorological Society, 89:1147, 2008. [ bib | DOI | ADS link ]

M. T. Woodhouse, G. W. Mann, K. S. Carslaw, and O. Boucher. New Directions: The impact of oceanic iron fertilisation on cloud condensation nuclei. Atmospheric Environment, 42:5728-5730, 2008. [ bib | DOI | ADS link ]

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