Effects of absorbing aerosols in cloudy skies: a satellite study over the Atlantic Ocean 1Max Planck Institute for Meteorology, Hamburg, Germany
2University of Hamburg, Hamburg, Germany
3International Max Planck Research School on Earth System Modelling, Hamburg, Germany
4Hadley Centre, Met Office, Exeter, UK
Received: 25 August 2009 – Published in Atmos. Chem. Phys. Discuss.: 02 October 2009 Abstract. We present a method for deriving the radiative effects of absorbing aerosols
in cloudy scenes from satellite retrievals only. We use data of 2005–2007
from various passive sensors aboard satellites of the "A-Train"
constellation. The study area is restricted to the tropical- and subtropical
Atlantic Ocean. To identify the dependence of the local planetary albedo in
cloudy scenes on cloud liquid water path and aerosol optical depth (AOD), we
perform a multiple linear regression. The OMI UV-Aerosolindex serves as an
indicator for absorbing-aerosol presence. In our method, the aerosol
influences the local planetary albedo through direct- (scattering and
absorption) and indirect (Twomey) aerosol effects. We find an increase of the
local planetary albedo (LPA) with increasing AOD of mostly scattering aerosol
and a decrease of the LPA with increasing AOD of mostly absorbing aerosol.
These results allow us to derive the direct aerosol effect of absorbing
aerosols in cloudy scenes, with the effect of cloudy-scene aerosol absorption
in the tropical- and subtropical Atlantic contributing
(+21.2 ± 11.1)×10−3 Wm−2 to the global top of the
atmosphere radiative forcing.
Revised: 28 October 2010 – Accepted: 07 February 2011 – Published: 16 February 2011
Citation: Peters, K., Quaas, J., and Bellouin, N.: Effects of absorbing aerosols in cloudy skies: a satellite study over the Atlantic Ocean, Atmos. Chem. Phys., 11, 1393-1404, doi:10.5194/acp-11-1393-2011, 2011.