Aerosol direct radiative forcing based on GEOS-Chem-APM and uncertainties Atmospheric Sciences Research Center, State University of New York, 251 Fuller Road, Albany, New York 12203, USA
26 Jun 2012
Received: 22 November 2011 – Published in Atmos. Chem. Phys. Discuss.: 03 January 2012 Abstract. Aerosol direct radiative forcing (DRF) plays an important
role in global climate change but has a large uncertainty. Here we
investigate aerosol DRF with GEOS-Chem-APM, a recently developed global
aerosol microphysical model that is designed to capture key particle
properties (size, composition, coating of primary particles by volatile
species, etc.). The model, with comprehensive chemistry, microphysics and
up-to-date emission inventories, is driven by assimilated meteorology, which
is presumably more realistic compared to the model-predicted meteorology.
For this study, the model is extended by incorporating a radiation transfer
model. Optical properties are calculated using Mie theory, where the
core-shell configuration could be treated with the refractive indices from
the recently updated values available in the literature. The surface albedo
is taken from MODIS satellite retrievals for the simulation year, in which
the data set for the 8-day mean at 0.05° (5600 m) resolution
for 7 wavebands is provided. We derive the total and anthropogenic aerosol
DRF, mainly focus on the results of anthropogenic aerosols, and then compare
with those values reported in previous studies. In addition, we examine the
anthropogenic aerosol DRF's dependence on several key factors, including the
particle size of black carbon (BC) and primary organic carbon (POC), the
density of BC and the mixing state. Our studies show that the anthropogenic
aerosol DRF at top of atmosphere (TOA) for all sky is −0.41 W m−2.
However, the sensitivity experiments suggest that the magnitude could vary
from −0.08 W m−2 to −0.61 W m−2, depending on assumptions regarding
the mixing state, size and density of particles.
Revised: 27 April 2012 – Accepted: 01 June 2012 – Published: 26 June 2012
Citation: Ma, X., Yu, F., and Luo, G.: Aerosol direct radiative forcing based on GEOS-Chem-APM and uncertainties, Atmos. Chem. Phys., 12, 5563-5581, doi:10.5194/acp-12-5563-2012, 2012.