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AGU: Geophysical Research Letters

 

Keywords

  • aerosol radiative forcing
  • urban aerosols

Index Terms

  • Atmospheric Composition and Structure: Aerosols and particles
  • Atmospheric Composition and Structure: Pollution: urban and regional
  • Atmospheric Composition and Structure: Troposphere: composition and chemistry
  • Atmospheric Composition and Structure: Instruments and techniques
  • Cryosphere: Remote sensing

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L04817, 5 PP., 2008
doi:10.1029/2007GL032879

Observations of enhanced aerosol longwave radiative forcing over an urban environment

A. S. Panicker

Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Pune, India

G. Pandithurai

Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Pune, India

P. D. Safai

Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Pune, India

S. Kewat

Physical Meteorology and Aerology Division, Indian Institute of Tropical Meteorology, Pune, India

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 μm 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 8.2 Wm−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.

Received 5 December 2007; accepted 25 January 2008; published 29 February 2008.

Citation: Panicker, A. S., G. Pandithurai, P. D. Safai, and S. Kewat (2008), Observations of enhanced aerosol longwave radiative forcing over an urban environment, Geophys. Res. Lett., 35, L04817, doi:10.1029/2007GL032879.

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