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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CONTENTS-CONTINUED

TABLES-CONTINUED

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Comparison of radar-estimated hourly snowfall accumulations and standard errors of estimates for
array averages and the nearest neighbor range bin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. [0
Summary of R values between indicated gage hourly SWE accumulations and the range bins
directly overhead (0.0 m S.I) and the range bins calculated by the reverse trajectory method for
the four indicated assumed fall speeds for larger snowflakes .............................: 11
Summary of optimization technique applied to selected Cleveland and Denver data sets of gage-
observed and radar-estimated hourly snowfall accumulations showing resulting a and .8 values ... D
Listing of the 11 storms for which the Albany, NY, volunteer (snow spotter) network was
partially or fully deployed during the 1995-96 winter and level II radar data are also available .... 17
Summary of optimized Ze-S relations based on hourly radar estimates of SWE overhead compared
with measured SWE from gages and snow boards, and from SWE estimated from the snow
board SD multiplied by the median snow density of 0.067 ................................ 29
Summary of results of applying the entire 1995-96 winter's optimized relation for gage 1 only,
Ze = 417 S2.2, to all five gages east-northeast of the Cleveland radar ......................... 29
Summary of results of applying the entire 1995-96 winter's optimized relation based on 14 snow
boards from 20 to 40 km from the Albany radar, Ze = DO S2.0, to 3 other groupings of snow

boards at farther ranges ........................................................... 32

Summary of storm total information for selected gages or snow boards in the Cleveland, Denver,

and Albany areas ................................................................ 36

Results of optimization technique applied to Cleveland lake effect storms and major synoptic
storms showing resulting a and .8 values .............................................. 42

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FIGURES

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Plots of normalized CTF (criterion function) versus the exponent of equation (1) for data sets
from five different gages ........................................................... 7
Plots of recommended Ze-S relationships for Cleveland and Denver areas .................... 14
Plot of all 698 hourly observations for Cleveland gages 1 and 2 against radar estimates using
the noted Ze-S relation ............................................................ 15
Similar to figure 3 but for 736 hourly observations based on 14 snow board sites located between
20 and 40 km range from the Albany radar ............................................ 18
Percent distribution of snow density based on 2328 hourly observations of SWE and SD from
73 sites ne~r Albany, NY .......................................................... 23
Percent distribution of snow density based on 62 high-resolution hourly observations of SWE
and SD from a Lakewood, CO, location. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 23
Albany, NY, area snow densities of figure 5 plotted against air temperature .................. 26
Lakewood, CO, hourly snow densities of figure 6 plotted against air temperature .............. 26
Plot of all 170 hourly snow board observations with SWE of at least 0.005 inch made by Denver's

gages 1, 2, and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 28

Similar to figure 9 except that SWE values were estimated for 176 hours by multiplying SD
observations of at least 0.10 inch by the median density of 0.067 . . . . . . . . . . . . . . . . . . . . . . . . . .. 28
Plot of the radar/gage ratios of table 8 versus distance from the Cleveland WSR-88D
illustrating radar underestimation with range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30
Plot of empirical correction curve that can be used to adjust the solid line data of figure 11 ...... 31

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