WMOD00562

• Title: Snow Accumulation Algorithm for the WSR-80D Radar: Second Annual Report
• Date: 6/1/1997
• Weather Modification - Doc Type: Report

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1. INTRODUCTION

The OSF (Operational Support Facility), located in Norman, Oklahoma, released a request for proposals
in the fall of 1994 seeking development of a SAA (snow accumulation algorithm). The SAA is intended
to be used with the recently-installed national network of NEXRAD (NEXt generation weather RADar).
Doppler weather radars. These installations are also referred to as WSR-88D (Weather Surveillance
Radar-1988 Doppler) radars. The NEXRAD network represents a major upgrade and improvement over
the aging systems it replaced (Crum et al., 1993).

Reclamation (Bureau of Reclamation) submitted a proposal to the OSF in mid-October 1994, which was
evaluated along with proposals from other Federal and Federally-supported agencies. An MOU
(memorandum of understanding) was signed the end of May 1995 among the NEXRAD Program, the
WSR-88D OSF, and Reclamation, which called for Reclamation to develop the SAA over a 3-year period.
The original MOU was modified in August 1995 to include collection of snow observations parallel to
the south shore of Lake Erie, east-northeast of Cleveland. Subsequent analysis of these snowfall and
radar measurements was expected to evaluate the ability of the developing SAA to detect and quantify
lake effect snowfall. A second modification in October 1996 tasked Reclamation with helping adapt the
SAA for real-time use and working with the NWS (National Weather Service) WFOs (Weather Forecast
Offices) at Cleveland and Minneapolis during the 1996-97 winter's real-time SAA testing.

The SAA converts radar measurements of equivalent (also called effective) reflectivity factor, Ze, into
estimates of the spatial distribution of SWE (snow water equivalent). The SAA also calculates SD (snow
depth) by multiplying SWE by estimated SD:SWE ratios. The SAA is limited to estimation of dry
snowfall. Complications in dealing with mixed rain and snow or melting snow with associated "bright
band" effects is beyond the scope of the requested work and resources available to accomplish it.

This annual report discusses Reclamation TSC (Technical Service Center) activities during the second
year of the 3-year effort to develop the SAA. Work done during the first year of SAA development was
reported by Super and Holroyd (1996). A prototype SAA was discussed in that report which was capable
of operating after the fact using Level II .data recorded on 8-mm tapes. As discussed by Crum et al.
(1993), Level II data are the most basic available to researchers. Level II data are the same as those
transmitted from the RDA (Radar Data Acquisition) computer to the RPG (Radar Product Generator)
workstation, where all algorithm processing is done.

The tasks performed during the second year of effort are paraphrased below with references given to the
tasks within the original MOU or its modifications.

1. Provide the annual report for the second year of effort by July 1, 1997 (specified in task 4 ofMOU
modification No.1).

Work done during the second year of SAA development is reported herein.

2. Reduce the precipitation gage charts for several lake effect storms of particular interest (task 3. of
MOU modification No.1).

As discussed by Super and Holroyd (1996), Reclamation operated a network of five Belfort Universal
gages, in protected locations, parallel to the south shore of Lake Erie during the 1995-96 winter.
SWE data from these gages have been extracted for all 24 storms identified during that unusually wet