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 meas urements from a high-sensitivity millimeter-wavelength radar and a collocat ed dual-frequency microwave radiometer to obtain height-resolved estimates of the liquid content of stratiform clouds. Comparisons with the aircraft m easurements 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 conten ts from 0.04 to 0.57 g m(-3) the mean difference between the aircraft and t he 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 m any scientific purposes.