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<br />1. INITRODUCTION <br /> <br />Approxima.tely 160 NEXRAD (NEXt generation weather RADar) units were installed across the United <br />States during the period 1991-1997 (Fulton et aI., 1998). Individual radars in this network are also <br />referred to as the WSR-88D (Weather Surveill!ance Radar - 1988 Doppler). The NEXRAD network <br />represents a major upgrade and improvement over the aging systems it replaced (Crum et aI., 1993). The <br />NEXRAD network of WSR-88Ds is operated by three Federal agencies, the National Weather Service, <br />the Federal Aviation Administration, and the U.S. Air Force. Consequently, NEXRAD is a tri-agency <br />cooperative effort among the Departments of Commerce, Transportation, and Defense. <br /> <br />The sole precipitation algorithm available on the WSR-88Ds has been the PPS (Precipitation Preprocess- <br />ing Subsystem), designed for rainfall but calibrated with data for tropical cumulus clouds. National <br />Weather Service (NWS) forecasters and others have a current need of an SAA (Snow Accumulation <br />Algorithm) capable of providing reasonably accurate real-time snow water equivalent (S) and snow depth <br />(SD) estimates based on effective reflectivity (Ze)' Awareness of PPS limitations with snow led the <br />NEXRAD OSF (Operational Support Facility) in Norman, Oklahoma, to sponsor Reclamation (Bureau of <br />Reclamation) efforts to develop the SAA described by Super and Holroyd (1996, 1997, 1998). <br /> <br />Implementation of the SAA in the NEXRAD network is presently awaiting hardware and software <br />upgrades to that system. This report presents the efforts supported by OSF (Operational Support <br />Facility) and the NOAA (National Oceanic and Atmospheric Administration) Office of Global Programs <br />GEWEX (Global Energy and Water Cycle Experiment) GCIP (Continental-Scale International Project) to <br />refine the SAA to improve its performance in at variety of challenging weather situations. <br /> <br />2. TASK SUMMARIES <br /> <br />Supplement Number 3 to the original Memorandum of Understanding (MOU) covers the period from <br />1 June 1998 to 1 October 1999, with a final 2 month extension for writing this report. The statement of <br />work (slightly reformatted for clarity) is: <br /> <br />The Reclamation TSC (Technical Service Center) investigations may include the following: <br />...examine additional data sets to optimize the Ze-S relations for regions such as Alaska and the <br />Sierra Nevada where the '96/'97 data were very sparse; <br />...investigate whether at least a seasonal average vertical profile of Ze should be used as part of a <br />range correction scheme; <br />...develop a "warning message" for the radar operators when bright band contamination appears <br />likely. <br /> <br />The work includes cooperation with OSF in a timely manner for arising questions about the SAA. Work <br />done under other funding (GCIP, Reclamation's Research and Technology Transfer Program), but related <br />to the SAA, was expected to be forwarded to OSF. <br /> <br />3. GCIP SUPPORT <br /> <br />3.1 A GCIP Report <br /> <br />Most of the SAA effort during this reporting peJriod was done in support of NOAA's GCIP program. <br />The following is an overview, based on a presentation, A Demonstration of the Operational Use of <br /> <br />1 <br />