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[aprssig] NWS Radar Future Directions (Part II)

Gerry Creager N5JXS gerry.creager at tamu.edu
Tue Mar 29 16:31:41 UTC 2005


Level II data are less processed than Level III images.  Level II data 
are sent as 100-radial subscans from each radar site, as soon as the 
100-radial subscan is completed.  A full volume scan is completed for 
each radar site every 5-6 minutes, depending on clear-air mode (6 min) 
or precip mode (5 min), and may be up to 80 MB in size.  The spectrum 
data includes reflectivity and velocity data.  These are the data 
Storm/Radar Lab, the various TV services, and the NWS use for storm 
tracks, and some of the flashier radar graphics.

We move *all* of the Level II data and maintain a 30-day cache of these 
data, as part of the Internet2 radar distribution project.  We also 
generate a lot of Level II images 
(http://mesonet.tamu.edu/products/radar/LevelII.html).  Level II data 
have a 1km x 1km resolution for reflectivity and .25km x .25km 
resolution for velicity data.  Also, instead of the 16-level intensity 
resolution for display colors, Level II data have 64 levels to play 
with.  Thus, the colors appear to transition more smoothly.

Again, when I generate single site data, I tend to do so in CED, or 
unprojected lat/lon format for Level II data.

NWS have standardized on Polar Stereographic projection for individual 
sites.  Getting a change to this will require between 1 and 4 years of 
paperwork and review.  A new product (like RIDGE) with a different 
projection is actually easier.

With the current package I use (Unidata Gempak) I'm only producing 
reflectivity, radial velocity and spectrum width (std dev of radial 
velocity) for our radar use here.  Of these, reflectivity at 0.5 deg is 
consistent with what most/all users are familiar with.

We're working on two things right now, CPU power allowing:
1.  Individual radar sites, with images prepared as soon as the volume 
scan is complete, for all of the Level II-enabled sites (currently 128 
of some 162 sites)
2.  A Level II CONUS mosaic with delivery as either a large GIF or via 
selected region via the Open Geospatial Consortium's Web Mapping Service 
specifications.

Regional mosaics and some special areas may be provided by special 
request, and depending on CPU and personnel available.

Right now, between the Level III mosaic and processing about 35 sites 
every 5 minutes, I'm keeping 4 1.6-2.0 GHz P4's busy.  We're doing 
several images on those individual sites for various applications/uses 
and it's processor intensive.

I'm going to try to continue to support the APRS/SkyWarn needs as best I 
can arrange.  Please let me know if there's a special requirement that 
you have that you need help with in this regard.  I'll be as honest as 
possible in getting things together, or admitting I can't help.

73, gerry
-- 
Gerry Creager -- gerry.creager at tamu.edu
Texas Mesonet -- AATLT, Texas A&M University	
Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.847.8578
Page: 979.228.0173
Office: 903A Eller Bldg, TAMU, College Station, TX 77843




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