Banks, JR, Brindley, HE, Hobby, M et al. (1 more author) (2014) The daytime cycle in dust aerosol direct radiative effects observed in the central Sahara during the Fennec campaign in June 2011. Journal of Geophysical Research: Atmospheres, 119 (24). 13861 - 13876. ISSN 2169-897X
Abstract
The direct clear-sky radiative effect (DRE) of atmospheric mineral dust is diagnosed over the Bordj Badji Mokhtar (BBM) supersite in the central Sahara during the Fennec campaign in June 2011. During this period, thick dust events were observed, with aerosol optical depth values peaking at 3.5. Satellite observations from Meteosat-9 are combined with ground-based radiative flux measurements to obtain estimates of DRE at the surface, top-of-atmosphere (TOA), and within the atmosphere. At TOA, there is a distinct daytime cycle in net DRE. Both shortwave (SW) and longwave (LW) DRE peak around noon and induce a warming of the Earth-atmosphere system. Toward dusk and dawn, the LW DRE reduces while the SW effect can switch sign triggering net radiative cooling. The net TOA DRE mean values range from -9 Wm-2 in the morning to heating of +59 Wm-2 near midday. At the surface, the SW dust impact is larger than at TOA: SW scattering and absorption by dust results in a mean surface radiative cooling of 145Wm-2. The corresponding mean surface heating caused by increased downward LW emission from the dust layer is a factor of 6 smaller. The dust impact on the magnitude and variability of the atmospheric radiative divergence is dominated by the SW cooling of the surface, modified by the smaller SW and LW effects at TOA. Consequently, dust has a mean daytime net radiative warming effect on the atmosphere of 153Wm-2.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | ©2014. American Geophysical Union. All Rights Reserved. |
Keywords: | Bordj Badji Mokhtar; Fennec; geostationary satellite observations; ground observations; Radiative effect of dust |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst for Climate & Atmos Science (ICAS) (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 16 Jul 2015 15:02 |
Last Modified: | 16 Jul 2015 15:02 |
Published Version: | http://dx.doi.org/10.1002/2014JD022077 |
Status: | Published |
Publisher: | American Geophysical Union (AGU) |
Identification Number: | 10.1002/2014JD022077 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:86230 |