Abstract
Abstract. Atmospheric mineral dust particles exert significant direct radiative forcings and are important drivers of climate and climate change. We used the GEOS-Chem global three-dimensional chemical transport model (CTM) coupled with the Fu-Liou-Gu (FLG) radiative transfer model (RTM) to investigate the dust radiative forcing and heating rate based on different vertical profiles for April 2006. We attempt to actually quantify the sensitivities of radiative forcing to dust vertical profiles, especially the discrepancies between using realistic and climatological vertical profiles. In these calculations, dust emissions were constrained by observations of aerosol optical depth (AOD). The coupled calculations utilizing a more realistic dust vertical profile simulated by GEOS-Chem minimize the physical inconsistencies between 3-D CTM aerosol fields and the RTM. The use of GEOS-Chem simulated vertical profile of dust extinction, as opposed to the FLG prescribed vertical profile, leads to greater and more spatially heterogeneous changes in the estimated radiative forcing and heating rate produced by dust. Both changes can be attributed to a different vertical structure between dust and non-dust source regions. Values of the dust vertically resolved AOD per grid level (VRAOD) are much larger in the middle troposphere, though smaller at the surface when the GEOS-Chem simulated vertical profile is used, which leads to a much stronger heating rate in the middle troposphere. Compared to the FLG vertical profile, the use of GEOS-Chem vertical profile reduces the solar radiative forcing at the top of atmosphere (TOA) by approximately 0.2–0.25 W m−2 over the African and Asian dust source regions. While the Infrared (IR) radiative forcing decreases 0.2 W m−2 over African dust belt, it increases 0.06 W m−2 over the Asian dust belt when the GEOS-Chem vertical profile is used. Differences in the solar radiative forcing at the surface between the use of the GEOS-Chem and FLG vertical profiles are most significant over the Gobi desert with a value of about 1.1 W m−2. The radiative forcing effect of dust particles is more pronounced at the surface over the Sahara and Gobi deserts by using FLG vertical profile, while it is less significant over the downwind area of Eastern Asia.
Highlights
GeoscientificMineral dust prModoucdedebl yDtheevweinlod permosieonnotf dry soil par- M3-D chemical transport model (CTM) aerosol fields and the radiative transfer model (RTM)
Values of the dust suggested that the direct radiative forcing of dust on regional vertically resolved AOD per grid level (VRAOD) are much and global scales may be comparable to, or even exceed, the larger in the middle troposphere, though smaller at the sur- forcing by anthropogenic aerosols
Net heating rate dust concentration were improved over the western coastal US where the dust was mainly influenced by the long-range transport from Asian and African source regions (VanCuren and Cahill, 2002; Yu et al, 2012; Zhang et al, 2013)
Summary
3-D CTM aerosol fields and the RTM. The use of GEOS- ticles at the land surface has been recognized as a leading. Values of the dust suggested that the direct radiative forcing of dust on regional vertically resolved AOD per grid level (VRAOD) are much and global scales may be comparable to, or even exceed, the larger in the middle troposphere, though smaller at the sur- forcing by anthropogenic aerosols A number of field programs have been carried out to measure the vertical distribution of aerosols, including the Dust and Biomass-burning Experiment (DABEX), Tropospheric Aerosol Radiative Forcing Observation Experiment (TARFOX), and Puerto Rico Dust Experiment (PRIDE) (Hueber et al, 1998; Russell et al, 1999; Maring et al, 2003; Johnson et al, 2008) These ground-based and/or aircraft measurements have provided valuable information, but are limited in spatial and temporal coverage.
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