GIDS-1 NMC/CAC Daily Surface Weather Map Imagery
     
     
     1.0  General Description
     
          The National Meteorological Center (NMC) and Climate Analysis
     Center (CAC) Upper Air Daily Weather Map Series imagery is one of
     several image datasets provided as part of the GEWEX Continental-scale
     International Project (GCIP) Initial Dataset One (GIDS-1). The surface
     map imagery covers the conterminous United States and parts of Canada
     and Mexico.  The NMC/CAC surface map imagery contains daily maps
     valid 1200 UTC for the entire GIDS-1 time period (01 February 1992
     through 30 April 1992). 
     
     2.0  Detailed Data Description
     
          The NMC/CAC Daily Weather Map Series publication is a weekly
     publication of the National Weather Service NMC Meteorological
     Operations Division and Climate Analysis Center. They are derived
     from operational maps produced by NMC. The surface weather map shows
     station data and the analysis (i.e., isobars, fronts, pressure centers) 
     valid at 1200 UTC. Tracks of well defined low pressure areas are indicated
     by a chain of arrows; locations of these centers at 06, 12, and 18 hours
     preceding map time are indicated by small white crosses in black squares.
     Areas of precipitation are indicated by shading.  The freezing line (32 deg
     F) is indicated as a labeled dashed line where applicable.  The weather
     reports depicted are only a fraction of those on which the analyses are
     based. Occasional apparent discrepancies between the printed station data
     and the analysis result from the absence of station reports not shown due
     to lack of space and clarity. The station data plots are based upon the
     standard international station model code and symbols.  Parameters plotted
     include: temperature (deg F), dewpoint temperature (deg F), barometric
     pressure at sea level (mb), amount of barometric change in past 3 hours
     (tenths of mb), barometric tendency in past three hours, visibility 
     (miles), wind direction, wind speed (knots), present weather, total amount
     of clouds, cloud type (high, middle, low levels), part of sky covered by
     lowest cloud, height of cloud base (feet), weather in past 6 hours, and
     amount of precipitation in last 6 hours (in).  
     
          Hard copy printed maps were collected weekly for the GIDS-1
     period (01 February 1992 through 30 April 1992). From this dataset each
     surface map was digitized (scanned) to a Graphics Interchange Format
     (GIF) file at 300 dots per inch resolution. The surface map imagery
     coincide with the  NMC/CAC Daily Weather Map Series 500-mb map
     imagery (1200 UTC), the GOES-7 infrared 8 km resolution imagery (1200
     UTC or closest available time), and composite radar reflectivity imagery
     (1200 UTC or closest available time). 
     
          These GIF images can be viewed using any standard GIF display
     software package. Further general information on GIF files, structure
     and format are provided in the References.
     
     2.1  Data Remarks
     
          These maps may be reproduced freely, with proper credit to the
     National Oceanic and Atmospheric Administration (NOAA).
     
     3.0  Quality Control Processing
     
          Other than digitizing and verification, no additional quality
     control was performed on the imagery by the UCAR/Office of Field
     Project Support. 
     
     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.