Atmos. Chem. Phys. Discuss., 11, 8777-8799, 2011
www.atmos-chem-phys-discuss.net/11/8777/2011/
doi:10.5194/acpd-11-8777-2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
The effect of optically thin cirrus clouds on solar radiation in Camagüey, Cuba
B. Barja and J. C. Antuña
Meteorological Center of Camagüey, INSMET, Finlay Av., km 7 1/2 Camagüey, Cuba

Abstract. Cirrus clouds play a key role in the radiation budget of the Earth system. They are an important aspect in the climate system, as they interact with the atmospheric radiation field. They control both the solar radiation that reaches the Earth surface and the longwave radiation that leaves the Earth system. The feedback produced by cirrus clouds in climate is not well understood. Therefore it is necessary to improve the understanding and characterization of the radiative forcing of cirrus clouds. We analyze the effect of optically thin cirrus clouds characterized with the lidar technique in Camagüey, Cuba, on solar radiation, by numerical simulation. Nature and amplitude of the effect of cirrus clouds on solar radiation is evaluated. Cirrus clouds have a cooling effect in the solar spectrum at the Top of the Atmosphere (TOA) and at the surface (SFC). The daily mean value of solar cirrus cloud radiative forcing (SCRF) has an average value of −9.1 W m−2 at TOA and −5.6 W m−2 at SFC. The cirrus clouds also have a local heating effect on the atmospheric layer where they are located. Cirrus clouds have mean daily values of heating rates of 0.63 K day−1 with a range between 0.35 K day−1 and 1.24 K day−1. The principal effect is in the near infrared spectral band of the solar spectrum. There is a linear relation between SCRF and cirrus clouds optical depth (COD), with −30 W m−2 COD−1 and −26 W m−2 COD−1, values for the slopes of the fits at the TOA and SFC, respectively in the broadband solar spectrum. Also there is a relation between the solar zenith angle and cirrus clouds radiative forcing displayed in the diurnal cycle.

Citation: Barja, B. and Antuña, J. C.: The effect of optically thin cirrus clouds on solar radiation in Camagüey, Cuba, Atmos. Chem. Phys. Discuss., 11, 8777-8799, doi:10.5194/acpd-11-8777-2011, 2011.
 
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