Observations of attenuation due to liquid-bearing stratocumulus clouds over Ottawa using a ground-based profiling radiometer

Abstract

Statistics on the attenuation due to non-precipitating, liquid-bearing overcast stratocumulus (Sc) clouds over Ottawa during the daytime are presented in this paper. Time series of Sc cloud attenuation are extracted from the brightness temperature data and retrievals from a ground-based multifrequency profiling radiometer. Frequencies of interest are 30 and 51.25 GHz; four elevation angles between 15 and 90 degrees (zenith) are considered. Both the MPM psila93 and Rosenkranz models are used to assess gaseous absorption using retrieved profiles ldquotopped uprdquo with the closest in time radiosonde data from a local station. Since most of the clouds in the data set contain some supercooled liquid, these extracted cloud attenuation data are compared to predictions from various dielectric constant models for pure liquid water using both the contemporaneously-retrieved liquid water path data and temperature at the cloud base as inputs.