Comparison of radar/radiometer retrievals of stratus cloud liquid‐water content profiles with in situ measurements by aircraft

In situ sampling of cloud droplets by aircraft in Oklahoma in 1997 is used to evaluate a ground‐based remote sensing technique for retrieving profiles of cloud liquid‐water content. The technique uses vertically pointing measurements from a high‐sensitivity millimeter‐wavelength radar and a collocated dual‐frequency microwave radiometer to obtain height‐resolved estimates of the liquid content of stratiform clouds. Comparisons with the aircraft measurements are made for 16 overpasses through thin cloud layers within a 1.5‐km radius of the remote sensor site. Over a range of liquid‐water contents from 0.04 to 0.57 g m−3 the mean difference between the aircraft and the radar/radiometer values was 0.02 g m−3, and the maximum difference was 0.09 g m−3. Although the number of comparisons is limited, these results suggest that the ground‐based estimates may be sufficiently accurate for many scientific purposes.