Global impact of smoke aerosols from landscape fires on climate and the Hadley circulation 1Department of Earth System Science, University of California, Irvine, CA 92697, USA
24 May 2013
*now at: NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
Received: 01 Oct 2012 – Published in Atmos. Chem. Phys. Discuss.: 25 Oct 2012 Abstract. Each year landscape fires across the globe emit black and organic carbon
smoke particles that can last in the atmosphere for days to weeks. We
characterized the climate response to these aerosols using an Earth system
model. We used remote sensing observations of aerosol optical depth (AOD) and
simulations from the Community Atmosphere Model, version 5 (CAM5) to optimize
satellite-derived smoke emissions for high biomass burning regions.
Subsequent global simulations using the adjusted fire emissions produced AODs
that were in closer agreement with surface and space-based measurements. We
then used CAM5, which included radiative aerosol effects, to evaluate the
climate response to the fire-aerosol forcing. We conducted two 52 yr
simulations, one with four sets of monthly cycling 1997–2009 fire emissions
and one without. Fire emissions increased global mean annual AOD by 10%
(+0.02) and decreased net all-sky surface radiation by 1% (1.3 W m−2).
Elevated AODs reduced global surface temperatures by 0.13 ± 0.01 °C.
Though global precipitation declined only slightly, patterns of precipitation
changed, with large reductions near the Equator offset by smaller increases
north and south of the intertropical convergence zone (ITCZ). A combination
of increased tropospheric heating and reduced surface temperatures increased
equatorial subsidence and weakened the Hadley circulation. As a consequence,
precipitation decreased over tropical forests in South America, Africa and
equatorial Asia. These results are consistent with the observed correlation
between global temperatures and the strength of the Hadley circulation and
studies linking tropospheric heating from black carbon aerosols with tropical
Revised: 12 Apr 2013 – Accepted: 24 Apr 2013 – Published: 24 May 2013
Citation: Tosca, M. G., Randerson, J. T., and Zender, C. S.: Global impact of smoke aerosols from landscape fires on climate and the Hadley circulation, Atmos. Chem. Phys., 13, 5227-5241, doi:10.5194/acp-13-5227-2013, 2013.