A field study of nocturnal stratocumulus; III. High resolution radiative and microphysical observations

Abstract

Abstract High resolution observations from a tethered balloon of nocturnal stratocumulus on three occasions are presented. Measurements of the microphysical properties of the clouds (drop‐size distributions, concentrations and liquid water contents) were obtained with an Axially Scattering Spectrometer Probe (ASSP). A ground based 95 GHz radiometer was used to infer the integrated liquid water path through the cloud. In the two thick clouds studied the drop‐size data show an almost monotonic increase of mean radius from cloud base to top. The liquid water content increases with height above cloud base at slightly less than the adiabatic rate and shows considerable variability towards cloud top. The observations support the concept of the inhomogeneous mixing of the cloudy air with the dry air entrained at the cloud top. Measurements were also made of infrared net radiative fluxes, and very good agreement is found with the theoretical fluxes from a high resolution radiative transfer scheme, using the ASSP drop spectra and liquid water contents, scaled by the 95 GHz radiometer data.