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<br />REPORT DOCUMENTATION PAGE Form Approved <br /> OMB No. 0704-0188 <br />Public reporting burden for this collection of information is estimated to average 1 hour per response. including the time for reviewing instructions. searching existing <br />data sources, gathering and maintaining the data needed. and completing and reviewing the collection of information. Send comments regarding this burden estimate <br />or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services. Directorate for Information <br />Operations and Reports, 1215 Jefferson Davis Highway. Suit 1204, Arlington VA 22202-4302. and to the Office of Management and Budget. Paperwork Reduction <br />Report (0704-01881, Washinaton DC 20503. <br />1. AGENCY USE ONLY (Leave Blank) 12. REPORT DATE 13. REPORT TYPE AND DATES COVERED <br /> November 1999 SuDol em ental <br />4. TITLE AND SUBTITLE 5. FUNDING NUMBERS <br />Snow Accumulation Algorithm for the WSR-88D Radar: Supplemental Report <br />6. AUTHORISI <br />Edmond W. Holroyd,lIl <br />7. PERFORMING ORGANIZATION NAMEISI AND ADDRESSIES) 8. PERFORMING ORGANIZATION <br /> REPORT NUMBER <br />Bureau of Reclamation <br />Technical Service Center R-99-11 <br />Civil Engineering Services <br />Materials Engineering and Research Laboratory <br />Denver, Colorado <br />9. SPONSORING/MONITORING AGENCY NAME IS I AND ADDRESSIES) 10. SPONSORING/MONITORING <br /> AGENCY REPORT NUMBER <br />Same <br />11. SUPPLEMENTARY NOTES <br />12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE <br />13. ABSTRACT (Maximum 200 wards) <br />This report documents an extension of work done on the Snow Accumulation Algorithm (SM) development for <br />NEXRAD WSR-88D radars. An expansion of operational testing using Level III data shows that the algorithm <br />continues to be robust. For the 1998-1999 season (November - April) a variety of accumulation products were <br />made available on the Internet for five radars across the Dakotas and Minnesota, including a regional mosaic. The <br />Ze-S relationship used was 150 R2.o. That network was expanded to 10 radars for the 1999-2000 winter season. <br />Issues involving the vertical gradient of reflectivity and snowfall continued to be prominent. The vertical gradient of <br />falling snow was used to generate a range correction which boosts integrations by a factor of three at 230 km. <br />Experimental work was performed that reduces the effects of virga at far ranges. A visualization routine was <br />created to display the vertical gradient in the lowest 5 km of altitude above the radar. Parts of that routine may be <br />useful in future efforts to reduce virga and bright band effects. A routine to sum many days of light or widespread <br />accumulations can guide hand editing of radar hybrid scan and occultation files to reduce blemishes in the SM <br />product. <br />14. SUBJECT TERMS 15. NUMBER OF PAGES <br />weather radar, NEXRAD, WSR-88D, Level II, Level III, Snow Accumulation Algorithm, 30 <br />precipitation, snow depth, snowfall, virga, Minnesota, North Dakota, South Dakota 16. PRICE CODE <br />17. SECURITY CLASSIFICATION OF 18. SECURITY CLASSIFICATION OF 19. SECURITY CLASSIFICATION OF 20. UMITATlON OF <br />REPORT THIS PAGE ABSTRACT ABSTRACT <br />UL UL UL UL <br /> <br />NSN 7540-01.280-5500 <br /> <br />Standard Form 298 (Rev. 2.89) <br />Prescribed by ANSI Std. 239.18 <br />298-102 <br />