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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depth difference becomes a filLX difference of 3630.4 g m-I S-I. This SLW flux was converted to a
precipitation flux over the 9.925 km distance between RRS and TAR, giving the approximate
precipitation rate required to completely account for the flux difference. The precipitation flux was
computed to be 0.3658 g m-2 s-:. Converting to a conventional precipitation rate. this becomes 1.32
mm h':, the rate necessary to account for the difference in SL W depth between RRS and TAR.
The a\'erage precipitation rate at TAR from 0900 to 1100 was 0.875 mm h -'. onlv about 66%
of the rate required to remove the excess SL \V. Studies of precipitation over the plateau during a
1991 :'\OA<\-Ctah field program by Huggins et al. (1992) showed that the precipitation maximum
was generally up\\ind of TAR. For the 1991 season the maximum was between the upwind edge of
the plateau and the middle, "\lth TAR precipitation being about 75% of the maximum. This suggests
that the average rate between RRS and Tl\R, on 7 February, was likely greater than the average
observed at TAR alone. Applying the 1991 percentage to the 7 February case suggests that the
precipitation observed could have accounted for about 90% of the SL W difference noted in the
radiometer comparison. Given the assumptions used in the simple calculation (such as the
representati\'eness of the SLW measurements), and reasonable errors in each parameter, this
comparison indicates that the up\vind-dmvnwind difference in SL W can be mostly be accounted for
by precipitation removal. To verify this further, a more detailed condensed phase water budget
across the plateau would be needed.
The tlnal period in Fig. 52b (1100-1200) shows the mobile transect from TAR back to RRS,
\\ith depth values again becoming nearly equivalent as the mobile reached RRS at about 1140. The
final period of comparison in Fig. 52c shows data from the mobile radiometer when it was near the
base of the plateau at HQ. The differences were similar to those noted in Fig. 52a, and reflect the
additional condensate that is produced when moist air is lifted over the \"indward slopes of the
plateau. It is interesting to note in all panels of Fig. 52 that the temporal trends in SLW were seen
in the data from both radiometers, regardless of position, indicating that, although orographic
influences were observed, the mesoscale influences were also detectable and in most cases were of
equal or greater magnitude.

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