WMOD00425

• Title: Demonstration of Improved Operational Water Resources Management Through Use of Better Snow Water Equivalent Information
• Date: 9/1/2002
• Weather Modification - Doc Type: Report

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During a 1998-99 winter test. real-time SAA accumulations (5 and SD products. based on NIDS
input) were provided for five radars: KRIS. Bismarck; KABR, Aberdeen; KMVX. Grand f'orks;
KMPX, Minnc,lpolis (the required site); and KDLH. Duluth. Accumulation updates were
provided hourly for all five radars on the approximate 4-km HRAP grid. A fl\'c-raoar composite
was also offered. Data from five additional radars (KTFX, Greal Falls; KMBX. Minot Air Force
Base; KGGW, Glasgow; KUDX. Rapid City; and KBLX, Billings) were added for the cool
season of 1999-2000. An 11th radar, KFSD. Sioux Falls, was added for the 2()(x).2001 cool
season. All these data were made available in real time on the Internet at our web site
hllp:/Iyampa.carthsci .do.usbr.gov:8080/awards/MnJindex .html (figure 2).

The SAA has heen
independently tested near
Reno. Nevada; Mi~soula.
Montana; and Salt Lake
City, Utah. As is typical
in the Western U.S.,
WSR.88D radars at these
location~ are on
mountaintops, al
elevations of 2530 m,
2395 m, and 1970 m,
respectively. These
radars will, thu~, have
more severe precipitation
overshooting problems
than radars in flat terrain,
especially when sampling
over valleys. Despite this
problem, there were ~omc
encouraging results. In
the Reno arca, 3-hour
SWEs estimated by the
SAA and eight mid-range
(77-10 150-km) gauges
showed a high correlation
coefficient r::; 0.83 (Cairns et aI., 1999). In Missoula. spoiler-reported SD measurements within
150 km and SAA 50s showed a moderate r ::; 0.64, despite the assumption of a fixed snow-
water ratio of 13: I (Barker et al.. 2(00). The Salt L1ke City area ~lUdy (Vasiloff. 2(XJ2) did not
use the range correction but rather multiplicative regression coefficients ("correction factors") to
adjust SAA SWE~ toward gauge SWEs. This was done beC<lU~e of the expected influence of the
nearby Wasatch Mountains on precipitation growth and beam hlockage. hoth of which are
unaccounted for by the range correction. After such corrections. there was good agreement (0.87
< r < 0.90) between these SWEs. The principal correction was for radar underestimation in the

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l- ~ t) ill ~ G. 31
.... ""'-~ ,..., ld..... ...... I~. '--,1_
:"'lionw ...." 1~-*-'._~_IO~'-/.............MooI
ITl...~_~_~ tlw__~~__."'l ~f..1 *'I't__ ~t--r--':'"Y2-

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'h

NEXIU.I> ',"SR-88D Hadal' SlUm Drpth ~lId ',"uteI'
Prod nth

._...~~~~Jo[..,...'...C1~..IIlIl(S.UJl'WIDWJlXl.U)W1Il-nIl""'"'"..~..
0..-, ...Mo._

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Figure 2.-North-central United States composite WSR.88D set of
11 radars from KDLH to KTFX, as displayed on Reclamation web site.

mountains.

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