A Study on Sulfate Optical Properties and Direct Radiative Forcing
Using LASG-IAP General Circulation Model |
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Authors: | LI Jiandong Zhian SUN LIU Yimin Jiangnan LI Wei-Chyung WANG and WU Guoxiong |
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Institution: | State Key Laboratory of Numerical Modeling for Atmospheric Sciences and
Geophysical Fluid Dynamics, Institute of Atmospheric Physics,
Chinese Academy of Sciences, Beijing 100029,
Atmospheric Sciences Research Center, State University of New York,
Albany, New York, USA 12203;Center for Australian Weather and Climate Research, Australian Bureau of Meteorology,
Melbourne, Victoria, Australia;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and
Geophysical Fluid Dynamics, Institute of Atmospheric Physics,
Chinese Academy of Sciences, Beijing 100029;Canadian Center for Climate Modeling and Analysis, University of Victoria,
Victoria, British Columbia, Canada;Atmospheric Sciences Research Center, State University of New York,
Albany, New York, USA 12203;State Key Laboratory of Numerical Modeling for Atmospheric Sciences and
Geophysical Fluid Dynamics, Institute of Atmospheric Physics,
Chinese Academy of Sciences, Beijing 100029 |
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Abstract: | The direct radiative forcing (DRF) of sulfate aerosols depends highly on the
atmospheric sulfate loading and the meteorology, both of which undergo
strong regional and seasonal variations. Because the optical properties of
sulfate aerosols are also sensitive to atmospheric relative humidity, in
this study we first examine the scheme for optical properties that considers
hydroscopic growth. Next, we investigate the seasonal and regional
distributions of sulfate DRF using the sulfate loading simulated from NCAR
CAM-Chem together with the meteorology modeled from a spectral atmospheric
general circulation model (AGCM) developed by LASG-IAP. The global
annual-mean sulfate loading of 3.44 mg m-2 is calculated to yield the
DRF of -1.03 and -0.57 W m-2 for clear-sky and all-sky conditions,
respectively. However, much larger values occur on regional bases. For
example, the maximum all-sky sulfate DRF over Europe, East Asia, and North
America can be up to -4.0 W m-2. The strongest all-sky sulfate DRF
occurs in the Northern Hemispheric July, with a hemispheric average of
-1.26 W m-2. The study results also indicate that the regional DRF
are strongly affected by cloud and relative humidity, which vary
considerably among the regions during different seasons. This certainly
raises the issue that the biases in model-simulated regional meteorology can
introduce biases into the sulfate DRF. Hence, the model processes associated
with atmospheric humidity and cloud physics should be modified in great
depth to improve the simulations of the LASG-IAP AGCM and to reduce the
uncertainty of sulfate direct effects on global and regional climate in
these simulations. |
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Keywords: | sulfate optical properties direct radiative forcing atmospheric general circulation model |
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