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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and the C.S. Bureau of Reclamation (CSBR) radiometer that collected data continuously in zenith
mode at the radar-radiometer site tRRS in Fig. 1). Tipping curve calibration factors (Decker and
SchroedeL 1991) were computed periodically throughout the field program for each radiometer.
These "tip car factors compensated for internal electronic variations, and allowed for quantitative
comparisons of the derived liquid and vapor depths. The USBR radiometer produced 2-min averages
of liquid and vapor depth throughout the field project, while the DRI mobile radiometer generally
recorded 1-4 s averages in mobile mode, or 5-min averages in stationary mode at HQ.
Operation of the mobile radiometer is described in detail by Huggins (1994, 1995). During
the 1994 field program the instrument \"'as driven over the roads shown in Fig. 1 to monitor SL W
upwind of. oyer, and dO\\TIwind of the Wasatch Plateau. Some experiments were designed for
comparison \\ith the stationary radiometer to document the natural change in SL W depth across the
plateau. Other experiments focussed on observing the SL \V inside and outside seeding plumes. to
determine whether SL \V was depleted by the effects of seeding. As a check on the calibration of the
mobile radiometer, integrated vapor depths were compared to sounding precipitable water values
during ten sounding launches in January, February and March 1994. On two occasions the
radiometer was parked at the ylt. Pleasant i\irport. During five of the other cases the radiometer was
at HQ, and during the other three cases the radiometer was on top of the Plateau. For the latter cases
the sounding precipitable water was computed upward from the height of the radiometer. The
comparative data are shov.n in Fig. 2 and reveal a very good correspondence betw'een sounding and
radiometer vapor values, with the linear regression line passing nearly through the origin and an
overall correlation of 0.962.
In addition to the mobile radiometer, a second mobile instrumented van was stationed at HQ
and used document seeding aerosol plume positions using an SF 6 detector and an NCAR ice nucleus
counter. The van was also equipped with a Panicle Measuring System 2DC laser imaging probe,
standard meteorological instruments, and a GPS for determining position. North American Weather
Consultants (\iAWC) handled operation of the van. This report makes use of l-s data from the SF 6
and KC-<\R counters.
Silver iodide seeding generators were positioned pan way up the western (windward) slope
of the plateau at HA.S and AHS in Fig. 1. The sites were at 2538 m and 2343 m, respectively, and

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