WMOD00447

• Title: Interagency Agreement Funds Usage Period Report - February 2001
• Date: 2/1/2001
• Weather Modification - Doc Type: Report

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For each site. S and SO products were made available via FTP and on the Internet for the past
I-hr. 2-hr. 3-hr, and 6-hr periods ending at the top 01 the hour and lor fixed 6-hr and 24-hrperiods.
The merged composite Sand SD products were available for the past 3-hr and 6-hr periods
ending at the top oflhe hour and lor fixed 24-hr periods. The lixed 6-hr products ended at 00, 06.
12, and 18 UTC, and the 24-hr products ended at 12 UTC. The fixed 6-hr and 24-hr products
were available for 7 days. Such products were made available for a half year but were
suspended in May lor the warm season. To examine the products, go to the lnlemet URL
<http://www.usbr.gov/rsmg>.thenselectNEXRADSnowAlgorithmProducts.This web site is
shown in Figure 1.

Range Correction

One significant contribution during the past year was development of a range correction
procedure. Two ways were investigated to deal with range correction. The simplest way is to
make alpha a function 01 range. calibrated by precision gage data lrom adequalely sheltered
locations. Another way is to examine the vertical profile of reflectivity or calculated S at a
particular range and use the seasonal gradient values at the first five tilts to create a range
correction relationship for farther ranges. Other empirical techniques may be applicable.

A Range-Dependent Alpha

Figure 2 shows the combined results of calculating an alpha that is range dependent. Six radars
(KCLE = Cleveiand, Ohio; KMPX = Minneapolis. Minnesota; KENX = Albany, New York; KFTG =
Denver. Colorado; KGJX = Grand Junction, Colorado; KBBX = Beale Air Force Base, California)
are represented and all reasonable gage information is included. While beta was fixed at 2.0 for
mosl cases, the KBBX points are for the alpha values with beta close to 2.0 l:t 0.3), as in table 1;
the unusually small alpha values did not encourage greater precision with a fixed beta.

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Figure 2. Plots of individual relations for the
variation of alpha with range. The thick curved
line is the VPR range correction used for the
1998-1999 season for the northern plains states.

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