Global Modeling of Tropospheric Aerosols and Their Contribution to Climate Variation
Catherine C. Chuang, PI
Keith E. Grant, Co-I
Abstract:
Atmospheric aerosols have significant effects on climate through their
impact on the Earth's radiation budget. Part of our earlier studies have been
focused on developing an understanding of global and regional sulfate aerosol
abundances and investigating their direct and indirect climate effects with a
fully coupled climate-aerosol model. Our simulations have indicated that the
anthropogenic sulfate aerosols may decrease the globally-averaged solar
radiation absorbed by the Earth-atmosphere system through the direct effect by
about -0.4 Wm-2. With different approaches for the formation of anthropogenic
sulfate and its relation to aerosol size distribution, the indirect forcing may
range from -0.6 to -1.6 Wm-2. This range reduces to -0.4 to -1.1 Wm-2 if a
prescribed marine background particle number concentration is universally
applied over the ocean.
To address the radiative impact of other significant aerosol types on
climate, we have developed emission inventories for carbonaceous and dust
aerosols. We have also developed a unique annual emission inventory of
anthropogenic SO2 for the years 1950 through 1994. Moreover, we have modeled
aerosol optical properties to account for changes in the refractive indices
with relative humidity and dry aerosol composition and developed
parameterizations of cloud response to aerosol abundance to evaluate the
importance of aerosol/cloud interactions on climate forcing. Based on our
strength in this area, we propose to extend our previous effort to simulate the
global distributions of all the important aerosol species and to assess their
potential to mask part of the warming expected from greenhouse gas emissions.
We will also examine the difference in forcing pattern and magnitude by direct
and indirect aerosol effects and determine the relative contribution of
industrial and non-industrial anthropogenic sources. The goal of this proposal
is to study the global aerosol cycle and to make a more quantitative evaluation
of the effects of aerosol emissions on the Earth's climate.
