A polarization lidar, dual-wavelength microwave radiometer, and radiosonde dataset from 19 winter storms studied over the Tushar Mountains in the 1985 and 1987 Utah–NOAA cooperative weather modification field campaigns are used to characterize embedded supercooled liquid water (SLW) clouds. The findings show the dominance of barrier-level. mildly supercooled (0° to −10°C) orographic clouds, as identified by the lidar from a midbarrier field site. The combined lidar and radiometer (with liquid water depths greater than or equal to 0.05 mm) data sample indicates an SLW cloud frequency of occurrence of about 73% of the time the lidar was operating, although only 51% of the lidar shots detected SLW clouds because of the frequent presence of range-limiting attenuation from snowfall. A significant development from this study is the application of a new autonomous computer algorithm for identifying SLW clouds store single normalized lidar shots, using only the height derivative of the returned signal and the minimum linear depolarization ratio. In terms of operational AgI cloud-seeding practices, we conclude that it is mainly the upper portions of SLW clouds with relatively warm cloud-base temperatures (≳ −7°C) that display potential for yielding increased snowfall, since only these clouds regularly produced significant (≥0.15 mm) radiometric liquid water depths.
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Sassen et al. (1993) studied this question.