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Last modified
7/28/2009 2:39:45 PM
Creation date
4/23/2008 11:58:46 AM
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Template:
Weather Modification
Title
Snow Accumulation Algorithm for the WSR-88D Radar, Version 1
Date
6/1/1996
Weather Modification - Doc Type
Report
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<br />Table 6. - Summary of significant snowfaIl periods sampled by Belfort gages east-northeast of <br />Cleveland, Ohio, during the 1995-96 winter. <br />Event Start date Stop date Storm Event Start date Stop date Storm <br />No. -hour (UTC) -hour (UTC) Type No. -hour (UTC) -hour (UTC) Type <br />1 04 Nov-OO 05 Nov-05 Major LEE: 13 12 Jan-OO 13 Jan-04 Minor Event <br />2 08 Nov-08 09 Nov-19 Major LEE: 14 24 Jan-12 25 Jan-05 Minor Event <br />3 15 Nov-12 16 Nov-18 Major LEE: 15 30 Jan-12 31 Jan-06 Minor Event <br />4 17 Nov-05 17 Nov-23 Minor Event 16 11 Feb-12 12 Feb-12 Minor Event <br />5 21 Nov-11 22 Nov-16 Major LEE: 17 14 Feb-OO 15 Feb-07 Minor Event <br />6 09 Dec-OO 12 Dec-17 Major LES 18 17 Feb-12 18 Feb-08 Minor Event <br />7 19 Dec-06 20 Dec-04 Major Synoptic 19 28 Feb-18 01 Feb-OO Major LES <br />8 20 Dec-lO 21 Dec-20 Major LES 20 02 Mar-12 03 Mar-04 Minor Event <br />9 22 Dec-12 24 Dec-20 Minor Event 21 03 Mar-04 04 Mar-05 Major LES <br />10 25 Dec-17 26 Dec-13 Major LES 22 08 Mar-23 09 Mar-12 Major LES <br />11 02 Jan-14 04 Jan-OO Major Synoptic 23 01 Apr-OO 02 Apr-03 Minor Event <br />12 09 Jan-21 10 Jan-14 Major LES <br /> <br />4. Data Processing <br /> <br />4.1 Belfort Gage Chart Reduction <br /> <br />Considerable care has been given to the time-consuming task of reducing Belfort gage charts. <br />Clock accuracy was generally within 5 minutes per week or less, and charts were changed <br />at least weekly. Start and stop times werH carefully noted, and an additional mid-week time <br />check was made as a minimum. Clocks which did not maintain an accuracy of 5 minutes per <br />week were adjusted (spring-wound clocks) or replaced (quartz-crystal electric clocks). <br /> <br />Charts were carefully read with at least 4-power magnification and good lighting to the <br />nearest 0.005 inch at hourly intervals. The resolution claimed for the Belfort gage is 0.01 <br />inch, but pen trace movements of 0.005-inch magnitude are readily apparent with careful <br />examination. <br /> <br />The "raw" chart reading was penciled in by each hour's line on the chart. Later, a second <br />check was made of each reading to detect any errors. After computer processing, hourly <br />snowfall accumulations were compared among neighboring gages and any obvious outliers <br />were checked yet again on the charts. Moreover, all high snowfall accumulations were given <br />an additional special check because they are uncommon but important in calculation of the <br />optimum Ze-S relationship. <br /> <br />Special attention was paid to chart readings near the daily time of chart overlap (0700-0800) <br />because the extra thickness of the overlapping paper causes the pen to rise then fall over a <br />few-hour period. The Belfort Charts No. 5-4047-B have a triple paper thickness. when <br />nonnally installed (two end flaps with one folded over), but one flap was cut off to miniinize <br />the vertical pen motion. Even then, readings near the overlap can be misleading if one <br />simply uses the chart readings; that is, thE~ pen trace relative to the horizontal lines that are <br />inked at 0.05-inch intervals on the charts. A better approach, which was used, is to compare <br />the differences in chart readings near the overlap with days having no precipitation. Because <br />7 rotations (traces) were obtained on most charts, non-precipitation periods were almost <br />. always available to compare against. Changes in the differences hour by hour provided the <br />best estimate of snowfall accumulation near times of chart overlap. The raw chart reading <br />was used at other times. These raw readings were entered into a computer file and a <br />program was written to calculate hourly differences. Because charts were operated in local <br /> <br />13 <br />
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