The effect of optically thin cirrus clouds on solar radiation in Camagüey, Cuba Meteorological Center of Camagüey, INSMET, Finlay Av., km 7 ½ Camagüey, Cuba
24 Aug 2011
Received: 14 Jan 2011 – Published in Atmos. Chem. Phys. Discuss.: 14 Mar 2011Abstract. The effect of optically thin cirrus clouds on solar
radiation is analyzed by numerical simulation, using lidar measurements of
cirrus conducted at Camagüey, Cuba. Sign and amplitude of the cirrus
clouds effect on solar radiation is evaluated. There is a relation between
the solar zenith angle and solar cirrus cloud radiative forcing (SCRF)
present in the diurnal cycle of the SCRF. Maximums of SCRF out of
noon located at the cirrus cloud base height are found for the thin and opaque
cirrus clouds. The cirrus clouds optical depth (COD) threshold for having
double SCRF maximum out of noon instead of a single one at noon was 0.083.
In contrast, the heating rate shows a maximum at noon in the location of
cirrus clouds maximum extinction values. 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 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 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.
Revised: 06 Jun 2011 – Accepted: 11 Jul 2011 – Published: 24 Aug 2011
Citation: Barja, B. and Antuña, J. C.: The effect of optically thin cirrus clouds on solar radiation in Camagüey, Cuba, Atmos. Chem. Phys., 11, 8625-8634, doi:10.5194/acp-11-8625-2011, 2011.