WMOD00591

• Title: Investigations of Winter Storms over the Wasatch Plateau during the 1994 NOAA-Utah Field Research Program - Final Report
• Date: 7/1/1996
• State: UT
• Weather Modification - Doc Type: Report

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This tlnal report summarizes the DRI investigations of weather systems, SL Wand seeding
experiments from the 1994 "!\OA-'\-Utah field program. Brief summaries of the main storm periods
are gi"'en. The SL W characteristics during those storm periods are presented, along vvith more
detailed studies of the spatial distribution ofSL\V over the Wasatch Plateau, and comparisons of
stationary and mobile SL \V measurements for one case study (7 February 1994). Two ground-based
cloud seeding experiments are described: one (26 Januarv 1994) which focusses on mobile
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radiometer measurements of SL W across seeding plumes, and a second which documents
microphysical and radar-detected seeding plumes from 19 February 1994. A summary of trace
chemistry analyses of snow samples collected throughout the 1994 field program is also presented.

II. 1994 ~O.-\..A-L"T.-\.H PROJECT AREA, ~STRU~IENTATIO~ and DATA

The 199-1- NOAA-Utah project area is sho\\>TI in Fig. 1. Soundings were taken from the Mt.
Pleasant .Airport (south of area in Fig. 1), primarily duringresearch aircraft flights. Huggins (1994)
describes the processing of soundings and provides Skew- T plots of all 1994 soundings. Field
headquarters (HQ) was located at the base of the plateau.
The DRI mobile radiometer was based at HQ, and collected data here in zenith-pointing
mode when not taking mobile observations. Huggins ( 1994) discusses the mobile radiometer data
collection, including the calculation of atmospheric retrieval coefficients. The coefficients used for
1994 radiometer data were computed from the combined set of 1991 and 1994 NOA.A.-Utah
soundings using a retrieval program described by Schroeder and West\vater (1991). Retrieval
coefficients were computed from starting altitudes of 1784 m (Mt. Pleasant Airport), upward at 200
m increments to 2982 m (plateau top). From these individual sets of retrieval coefficients, a height
dependent relationship was developed. Sensitivity tests were conducted on several portions of the
actual 1994 mobile radiometer data, during periods when the radiometer height changed mar~(edly.
The results showed that the 1\\'0 sets of coefficients, computed from the lowest and highest starting
altitudes, produced a nearly constant differenc~ of 0.05 mm in liquid water depth, regardless of
altitude. The differences noted in vapor depth were insignificant
For final data processing, a set of coefficients that was an average benveen the 1\\'0 extreme

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