WMOD00283

• Sponsor Name: USBR, Technical Service Center, River Systems 7 Meteorology Group
• Project Name: Use of NEXRAD WSR-88D Radar Snow Accumulations Algorith in the GCIP LSA-NC
• Title: Use of NEXRAD WSR-88D Radar Snow Accumulations Algorith in the GCIP LSA-NC
• Prepared For: USBR Technical Service Center
• Prepared By: Arlin B. Super
• Date: 1/1/1998
• State: MN
• Weather Modification - Doc Type: Report

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Considerable programming and testing were needed to produce a version of the BAA
that could use Level III data. The Level III product is in the form of binary files
intended for visual display, not for use as discrete digital dBZ values. Each Level
III reflectivity interval had to be assigned a dBZ value. Use of midpoints was
shown to be too simplistic for greater reflectivities. However, the BAA can now run
successfully with archived Level III reflectivity files.

Parallel runs of the SAA, using Level II and Level III reflectivities as input, were
made for five major Minnesota snow storms, one with mixed rain and snow. The
degree of agreement was shown to be quite good, especially at ranges less than 150
km where radar estimates are most reliable. Most Level III runs had area average
SWE accumulations within 10 percent or less of the standard Level II runs for the
same volume scans, at least within 150 km range. These results indicate that use
of archived Level III data from Minnesota snow storms provides quite reasonable
SWE estimates using Level II estimates as the standard.

The next step in this applied research will be to continue work on the VPS range
correction scheme so that the SAA can apply appropriate corrections for all ranges
between about 50 and 150 km and perhaps farther. It would, of course, be very
desirable to test this scheme against "ground truth" SWE observations. Accurate
surface measurements of snowfall, either of depth or SWE, are difficult to find.
However, attempts will be made to find the means to test the SAA range correction
scheme against some surface observations.

5. REFERENCES

Andrieu, H. and J.D. Creutin, 1995: Identification of Vertical Profiles of Radar
. Reflectivity for Hydrological Applications Using an Inverse Method: Part I:
Formulation. Journal of Applied Meteorology, 34, 225-239.

Crum, T.D., R. L. Alberty and D. W. Burgess, 1993: Recording, Archiving and
Using WSR-88D Data. Bulletin of the American Meteorological Society, 74,645-
653.

Joss, J. and R. Lee, 1995: The Application of Radar-Gauge Comparisons to
Operational Precipitation Profile Corrections. Journal of Applied Meteorology,
34, 2612-2630.

Joss, J. and A. Waldvogel, 1989: Precipitation Estimates and Vertical Reflectivity
Profile Corrections. Pre prints, 24th Conference on Radar Meteorology, American
Meteorological Society, Tallahassee, FL, March 27-31,682-688.

Joss, J. and A. Waldvogel, 1990: Precipitation Measurements and Hydrology. Radar
in Meteorology, D. Atlas, Ed., American Meteorological Society, 577-606.

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