Partly due to aerosol effects stratocumulus clouds vary considerably in liquid water path (LWP), geometrical thickness (h) and droplet number concentration (Nc). Cloud models have been developed to simulate h and Nc using satellite retrieved cloud optical thickness () and effective radius (re) values. In this paper we examine the consistency between LWP and h values inferred from the Spinning Enhanced Visible and Infrared Imager (SEVIRI) onboard METEOSAT-8. The use of METEOSAT-8 data means that time series of LWP and h can be validated at a 15-minute resolution, and used for examining the first indirect aerosol effect. For single-layered stratocumulus clouds the LWP and h retrievals from SEVIRI are compared to corresponding ground-based observations at two Cloudnet sites. A study on the sensitivity of the cloud model to the uncertainties in SEVIRI retrievals of and re reveals that h and Nc simulations are only accurate for clouds with effective radii larger than 5 m. The SEVIRI and ground-based retrievals of LWP and h show very good agreement, with accuracies of about 15 g m-2 and 20 m, respectively. This agreement could only be achieved by assuming sub-adiabatic profiles of droplet concentration and liquid water path in the cloud model. The degree of adiabaticity for single-layered stratocumulus clouds could be quantified by simultaneous analysis of SEVIRI and ground-based LWP and h values, which suggests that stratocumulus clouds over North Western Europe deviate, on average, from adiabatic clouds.
RA Roebeling, S Placidi, DP Donovan, HWJ Russchenberg, AJ Feijt. Validation of liquid cloud property retrievals from SEVIRI using ground-based observations
published, Geophys. Res. Lett., 2008, 35