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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were made. There are lingering localized errors to work on, such as virga and bright band
effects; but for now, forecasters can be alerted to their effects by the natures of the patterns (rings
and intense gradients) in the SAA output.

Interaction with water resources managers at a series of meetings with water operations
managers, people from river forecast centers, and NOHRSC researchers and active
communications with water managers is leading to better understanding of the NEXRAD
SWE products and how they may be integrated into the operational NOHRSC SNODAS system
that will replace the SEUS.

3.3 SAA Supplemental Report (Holroyd, 1999)

This report documents an extension of work done on the SAA development for NEXRAD
WSR-88D radars. An expansion of operational testing using Level ill data shows that the
algorithm continues to be robust. For the 1998-99 season (November-April), a variety of
accumulation products were made available on the Internet for five radars across the Dakotas and
Minnesota, including a regional mosaic. The Ze-S relationship used was 150 R2.O. That network
was expanded to 10 radars for the 1999-2000 winter season.

Issues involving the vertical gradient of reflectivity and snowfall continued to be prominent. The
vertical gradient of falling snow was used to generate a range correction which boosts
integrations by a factor of three at 230 km. The use of this correction scheme appears to be
appropriate when compared to surface observations. Experimental work was performed that
reduces the effects of virga at far range. A visualization routine was created to display the
vertical gradient in the lowest 5 km of altitude above the radar. Parts of that routine may be
useful in future efforts to reduce virga and bright band effects.

Work should continue to examine the vertical gradient issue to identify the best style of
algorithm. One that can simultaneously adjust for virga, bright band, and range correction would
be preferred. In addition, individual radar hybrid scan and occultation files can be adjusted by
hand editing to reduce localized errors in the SAA product, caused mainly by anomalous echo
enhancements or reductions.

4. SAA DEVELOPMENT

4.1 Background and Approach

The SAA was developed from 1995-98, with support from the WSR-88D Operational Support
Facility (now Radar Operations Center) in Norman, Oklahoma. The development was
thoroughly described in Super and Holroyd (1998), and the detail of that report will not be
repeated here. Nevertheless, some background is needed because the SAA lies at the heart of the

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