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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 estimc\ted to average 1 hour per response. including the time for reviewing. IRStcuCttons, searctlingex\sitfig <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 (0704-01 B8}. Washington DC 20503_ <br />1. AGENCY USE ONLY (Leave Blank) 2, REPORT DATE 3. REPORT TYPE AND DATES COVERED <br /> July 1998 Final <br />4. TITLE AND SUBTITLE 5. FUNDING NUMBERS <br />Snow Accumulation Alqorithm for the WSR-88D RADAR: Final Report <br />6. AUTHOR(S) <br />Arlin 8, Super and Edmond W, Holroyd, III <br />7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION <br /> REPORT NUMBER <br />Bureau of Reclamation <br />Water Resources Research Laboratory R-98-06 <br />Technical Service Center (Previously printed as R-98-05). <br />Denver, Colorado <br />9. SPONSORINGlMDNITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING <br /> AGENCY REPORT NUMBER <br />Same <br />11. SUPPLEMENTARY NOTES <br />Hard copy available at the Technical Service Center, Denver, Colorado <br />12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE <br />Available from the National Technical Information Service, Operations Division, <br />5285 Port Royal Road, Sprinqfield, Virqinia 22162 <br />13, ABSTRACT (Maximum 200 words) <br />This final report mostly describes the final of three years of SAA (Snow Accumulation Algorithm) development for NEXRAD <br />WSR.88D radars, An optimization technique applied to special snoWfall observations and Level II reflectivity measurements <br />determined Ze-S (reflectivity-snoWfall) relationships for radars in severed climatic zones. These relationships were similar for <br />most sites with standard power law coefficients near 150 and exponents near 2.0. Significant underestimation at longer ranges <br />was evident at all radars, particularly with shallow storms, The SAA now has a range correction scheme and suggestions are <br />given for determining appropriate coefficients for it. <br />The SAA was successfully field tested in real-time in Ohio, Minnesota, and New Ymk, The SAA produced reasonably accurate <br />estimates of storm-total snow water equivalent for all test areas, well correlated with surface observations, Customized hybrid <br />scans were required in order to use the lowest practical beam tilt. The vertical profile of Ze changes the Ze-S relationship with <br />higher elevation scanning, <br />The SAA is operationally ready for use at those few radars with suitable hardware. However, more powerful computers will be <br />needed before SAA availability on all NEXRAD units, <br />Recommended SAA improvements include identification of bright band contamination, handling far range virga, and adjusting for <br />longer range underestimation of snoWfall. <br />14_ SUBJECT TERMS 15. NUMBER OF PAGES <br />radar! NEXRADI WSR-88D! snow! snow density! snoWfall! precipitation! radar snow! snow algorithm! 75 <br />radar precipitation algorithm 16. PRICE CODE <br />17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF <br />OF REPORT OF THIS PAGE OF 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 SId, 239-18 <br />298-1 02 <br /> <br /> <br />