Atmos. Chem. Phys. Discuss., 13, 22931-22977, 2013
© Author(s) 2013. This work is distributed
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Satellite observations of cloud regime development: the role of aerosol processes
E. Gryspeerdt, P. Stier, and D. G. Partridge
Department of Physics, University of Oxford, UK

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 covariability to the observed correlations.

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 three times.

We find an increased occurrence of transitions into the stratocumulus regime over ocean with increases in MODIS Aerosol Index (AI), consistent with the hypothesis that aerosols increase the 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 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. Discuss., 13, 22931-22977, doi:10.5194/acpd-13-22931-2013, 2013.
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