GIST WSI NOWrad Imagery
     
     
     1.0  General Description
     
          The WSI Corporation NOWrad product radar reflectivity composite
     imagery is one of several image datasets provided in the GEWEX
     Continental-scale International Project (GCIP) Integrated Systems Test
     (GIST). The NOWrad imagery covers a sector (approx 8 deg latitude by
     12 deg longitude box) over the Central United States.  The NOWrad sector
     was generally fixed over the GIST domain but moved slightly depending
     upon areas of active weather. The NOWrad imagery contains daily
     composites valid 1200 UTC (or closest available time) for the GIST time
     period (01 April 1994 through 31 August 1994).  
     
     2.0  Detailed Data Description
     
          WSI Corporation routinely ingested radar information from
     operational National Weather Service radars in the United States.  From
     this information, WSI produced national "NOWrad" imagery every 15
     minutes which was composited from simultaneous reflectivity images of
     multiple radars.  WSI performed "real-time" ground clutter suppression on
     the data during the compositing procedure to remove false reflectivity
     patterns.  In the case of different reflectivity values from different
     radars at the same pixel, the highest value was used in the composite.
     Once the national composite processing was completed, both the national
     composite (8 km resolution) and high resolution regional imagery (2 km
     resolution) were available for transmission to WSI clients.  The National
     Severe Storms Forecast Center (NSSFC) in Kansas City, MO, received and
     reformatted the high resolution regional data into their McIDAS computer
     system.  NSSFC used five "floating" sectors which were routinely
     geographically moved depending upon severe weather location.  During the
     GIST experiment, NSSFC fixed one of these sectors over the GIST
     domain, whenever possible. 

          The NOWrad imagery was collected every 15 minutes during the
     GIST period (01 April 1994 through 31 August 1994) and archived in
     McIDAS-X format.  From this dataset a representative daily image was
     selected at 1200 UTC or closest available time, to coincide with the
     National Meteorological Center ETA Model Daily Weather Map imagery
     (1200 UTC) and GOES-7 Infrared image.  The selected daily images were
     translated to Graphical Interchange Format (GIF). These images were
     mapped and color enhanced using the standard WSR-88D (formerly
     NEXRAD) reflectivity breakpoints.  A "color bar" legend has been
     included on each image.
     
          These GIF images can be viewed using any standard GIF display
     software package. However, any additional detailed information from the
     original files (i.e., pixel reflectivity values, navigation, etc.) are not
     retrievable from the GIF image, but can be obtained from the actual data
     available from the UCAR Office of Field Project Support (UCAR/OFPS). 
     
     2.1  Detailed Format Description
     
          General information on GIF files, structure and format are provided
     in the References.
     
     2.2  Data Remarks
     
          All daily images are valid for 1200 UTC or closest available time. 
     Imagery was unavailable for 940807, 940821, 940827, 940828.
     
     3.0  Quality Control Processing
     
          No additional quality control or re-navigation was performed on the
     imagery by the UCAR/OFPS. OFPS did overlay the map and enhance the
     imagery before conversion to GIF files.
     
     
     4.0  References
     
     Kay: Graphics File Formats, 2/E.  ISBN: 0-07-034025-0, McGraw Hill.
     
     Luse, M: Bitmapped Graphics Programming in C++. ISBN: 0-201-
          63209-8, Addison-Wesley.