%0 Journal Article %J Geophysical Research Letters %D 2008 %T Observations of enhanced aerosol longwave radiative forcing over an urban environment %A Panicker, A. S. %A Pandithurai, G. %A Safai, P. D. %A Kewat, S. %X

Collocated measurements of sun/ sky radiance, aerosol chemical composition and radiative fluxes have been utilized to estimate longwave aerosol radiative forcing over Pune, an Indian urban site during dry winter [Dec2004 to Feb2005] by two methods. Hybrid method which uses observed downwelling and modeled upwelling longwave fluxes for different aerosol loadings yielded a surface forcing of 9.4 Wm(-2). Model approach includes utilization of skyradiometer derived spectral aerosol optical properties in the visible and near infra-red wavelengths, modeled aerosol properties in 1.2-40 mu m using observed soot and chemical composition data, MODIS water vapor and TOMS column ozone in a radiative transfer model. Estimates from model method showed longwave enhancement of 6.5 and 8.2Wm(-2) at the surface with tropical model atmosphere and temporally varying profiles of temperature and humidity, respectively. Study reveals that about 25% of the aerosol shortwave cooling is being compensated by increase in longwave radiation due to aerosol absorption.

%B Geophysical Research Letters %I AMER GEOPHYSICAL UNION %C 2000 FLORIDA AVE NW, WASHINGTON, DC 20009 USA %V 35 %P L04817 %8 FEB %G eng %N 4 %3 Foreign %4 3.505 %R 10.1029/2007GL032879