Satellite observations of cloud regime development: the role of aerosol processes Department of Physics, University of Oxford, UK
03 Feb 2014
Received: 04 Jul 2013 – Published in Atmos. Chem. Phys. Discuss.: 30 Aug 2013 Abstract. Many different interactions between aerosols and clouds have been postulated,
based on correlations between satellite retrieved aerosol and cloud
properties. Previous studies highlighted the importance of meteorological
covariations to the observed correlations.
Revised: 05 Dec 2013 – Accepted: 15 Dec 2013 – Published: 03 Feb 2014
In this work, we make use of multiple temporally-spaced satellite retrievals
to observe the development of cloud regimes. The observation of cloud regime
development allows us to account for the influences of cloud fraction (CF) and
meteorological factors on the aerosol retrieval. By accounting for the
aerosol index (AI)-CF relationship, we reduce the influence of meteorological
correlations compared to "snapshot" studies, finding that simple
correlations overestimate any aerosol effect on CF by at least a factor of two.
We find an increased occurrence of transitions into the stratocumulus regime
over ocean with increases in MODIS AI, consistent with the hypothesis that
aerosols increase stratocumulus persistence. We also observe an increase in
transitions into the deep convective regime over land, consistent with the
aerosol invigoration hypothesis. We find changes in the transitions from the
shallow cumulus regime in different aerosol environments. The strength of
these changes is strongly dependent on Low Troposphere Static Stability and
10 m windspeed, but less so on other meteorological factors.
Whilst we have reduced the error due to meteorological and CF effects on the
aerosol retrieval, meteorological covariation with the cloud and aerosol
properties is harder to remove, so these results likely represent an upper
bound on the effect of aerosols on cloud development and CF.
Citation: Gryspeerdt, E., Stier, P., and Partridge, D. G.: Satellite observations of cloud regime development: the role of aerosol processes, Atmos. Chem. Phys., 14, 1141-1158, doi:10.5194/acp-14-1141-2014, 2014.