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I I I I I I I I I I I I I I I I I I I ABSTRACT - Analyses of data collected during the 1991 Utah/NOAA Research Field Program are described. The Desert Research Institute had primary responsibility for describing the evolution of supercooled liquid water over the Wasatch Plateau, and comparing the results of liquid water studies with results from similar work in the Tushar Mountains of southern Utah. A new technique of data collection using a mobile microwave radiometer is described and results of numerous experiments are presented. The storms that occurred during the 1991 Field Program are described in terms of their synoptic characteristics, the evolution of locally measured meteorological variables, and cloud characteristics as observed by ground-based and satellite remote sensing platforms. Preliminary results of one experiment which made use of a spectral radiometer on the NASA ER-2 research aircraft are also presented. Fourteen storm periods were identified, with the majority developing in northerly or northwesterly upper level flow due to the persistent presence of a high pressure ridge in the vicinity of the West Coast during much of January and February 1991. Several storms in March developed in warmer and wetter southwesterly flow. Supercooled liquid water showed a slight preference for prefrontal occurrence, but not as predominantly as during prior Utah/NOAA field seasons in the Tushar Mountains. ~~per~~~ liqui~..~~~._1E.ost fr~~~~x.observed. ~h~Il._mgHJltNntOl! and cloJ!{ljL la~.!- winds were southwesterlxJqJ!2!th~!~!.!X' .The largest liquid depths occurred with winds from 240-2700. Similar to results from other geographic areas, the vertical location of liquid over the Wasatch Plateau was typically within two kilometers of the underlying terrain, and within a temperature range of 00 to -100 C. The largest radiometric liquid depths were measured coincidently with the warmest temperatures at the tops of sounding saturated layers. In the absence of valley-based stable layers or inversions, it appeared that seeding material from ground-based generators could be transported to the SL W region of clouds because of its proximity to the terrain, but that the material would frequently encounter temperatures that were not conducive to nucleation by standard AgI seeding agents. Supercooled liquid flux was computed from radiometer liquid and mountaintop winds (adjusted to simulate cloud layer winds). About 86% of the total seasonal flux was contained in the five largest storms. Total precipitation and total liquid flux were found to be weakly linearly correlated. Radiometer scans and mobile radiometer experiments provided more detailed information on the spatial distribution of supercooled liquid water than has been possible in prior 111