Station Subsets

Most WXP programs use city database files to search for station locations.  WXP provides a couple of ways to subset the list of stations so that not all stations are plotted or printed out.

Plot Domain

For most plotting programs, only those stations that are within the established plot domain.  For gridding applications, the objective analysis requires stations outside the plot domain to produce proper gridpoint values.  Therefore, the domain is extended by an extra 3 gridpoints in each direction.  For example:

   sa_parse -re=mw -cu -id=all

will only list those stations in the Midwest region.

Station Priorities

Each station in the city database is prioritized. Station priorities are assigned from 1 (highest, a city like Chicago) to 6 (lowest).  For most graphical applications the station priority is set automatically.  To manually set the priority, use the stat_prior resource.  Once set, all lower priority stations are filtered out of the plot.

Station Identifiers

The simplest means for searching for a specific station is to list it with the identifier resource.  Any number of stations can be listed separated by commas if more than one station is needed.

sa_parse -cu -id=KPHL,KIAD,KDEN
Date: 18Z 4 JUN 98

KIAD 041751Z 22008KT 10SM BKN037 BKN050 20/12 A2982 RMK AO2 SLP095 T02000122 10206 20161 58011
KDEN 041753Z 04011KT 1/4SM R35L/4000VP6000FT DZ BR OVC001 06/06 A2986 RMK AO2 SFC VIS 1 1/2 SLP091 P0000 60000 T00610061 10078 20056 53003
KPHL 041754Z 28018KT 10SM SCT060 BKN250 20/07 A2979 RMK AO2 SLP086 T02000072 10206 20139 58016

The station identifier resource has the ability to parse for more than a list of stations.  Here is a list of keywords:

• Name=station_name -- This can be used to parse for the station name (column 1) out of the city database file.  An example would be "name=cleveland". The names can be abbreviated.  The program uses the first one that matches.
• ST=state -- This uses the name of the state.  If the state is 2 characters, it is the state abbreviation such as "ST=PA".   If it is 5 characters, it is the state and country, such as "ST=MN_US".
• CN=country -- This uses the 2 character name of the country such as "CN=DL" for Germany.
• ID=ident -- This uses the 3 or 4 letter identifier (ICAO).   The "ID=" can be omitted.
• Ra<lat,lon,range -- This uses all stations that are within range km of the specified center point lat,lon.
• P=prior -- This uses all stations that have exactly that priority.
• P<prior -- This uses all stations that have that priority or less.  This is the equivalent of specifying the stat_prior resource.
• P>prior -- This uses all stations that have that priority or greater.
• Lat<latitude -- This uses all stations that have a latitude less than or equal to latitude.
• Lat>latitude -- This uses all stations that have a latitude greater than or equal to latitude.
• Lon<longitude -- This uses all stations that have a longitude less than or equal to longitude.
• Lon>longitude -- This uses all stations that have a longitude greater than or equal to longitude.
• Elev<elevation -- This uses all stations that have an elevation less than or equal to elevation.
• Elev>elevation -- This uses all stations that have an elevation greater than or equal to elevation.
• WMO=wmo -- This uses the station with this WMO number.
• WMO<wmo -- This uses all stations that have an WMO number less than or equal to wmo.
• WMO>wmo -- This uses all stations that have an WMO number greater than or equal to wmo.