Station Data is also supported within GrADS to a limited extent. Station data consists of data points distributed essentially randomly within the four dimensions.
Currently, station data operations and display are supported for three distinct dimension environments:
X, Y varying (horizontal X, Y plot)
Z varying (vertical profile)
T varying (time series)
Operations may be done on station data as with gridded data. Operations between grids and station data are not supported.
Operations between station data are defined as being the operation performed on data points that have exactly the same varying dimension values.
For example, if T is the only varying dimension, the expression:
display ts-ds
would result in a time series of station data reports being retrieved for two seperate variables. Then, for station reports having exactly the same time, the operation is performed. Note that duplicates are ignored, with the operation being performed between the first occurences encountered.
When both X and Y are both fixed dimensions, the variable specification may include a station identifier, which specifies a local override for both lat and lon.
The syntax for this would be:
varname(stid=ident)
The station identifiers are case insensitive.
Some functions do not support station data types. These are:
hdivg hcurl vint maskout ave aave tloop
When X and Y are varying, station data values are displayed as numbers centered at their locations. If two expressions are supplied on the display command (ie, display ts;ds) then two values are displayed, above and below the station location. The display is controlled by the following set commands:
set ccolor color
set dignum digits
set digsiz size
set stid on|off
The 'set stid' command controls whether the station identifier is displayed with each value.
GrADs will plot station models from station data. This is enabled by:
set gxout model
The appropriate display command is:
display u;v;t;d;slp;delta;cld;wx;vis
where:
- u and v are the wind components. A wind barb will be drawn using these values. If either is missing, the station model will not be plotted at all.
- t, d, slp, and delta are plotted numerically around the station model:
t slp
vis wx O delta
d
- cld is the value of the symbol desired at the center of the station model. Values 1 to 9 are assumed to be the marker types (ie, circle, square, crosshair, etc). Values 20 to 25 are assumed to be cloudiness values:
20 - clear
21 - scattered
22 - broken
23 - overcast
24 - obscured
25 - missing (M plotted)
- wx is the value of the wx symbol (see 'plot wxsym') to be plotted in the wx location.
- vis is the visibility as a real number. It will be plotted as a whole number and a fraction.
When any of these items are missing (other than u and v), the model is plotted without that element. To represent a globally missing value, enter a constant in the display command. For example, if the delta were always missing, use:
display u;v;t;d;slp;0.0;cld
The station models respond to the usual set commands such as 'set digsiz', 'set dignum', 'set cthick', 'set ccolor'.
In addition, there is:
set stnopts <dig3> <nodig3>
which will cause the model to plot the number in the slp location as a three digit number, with only the LAST three digits of the whole number plotted. This allows the standard 3 digit sea level pressure to be plotted by enabling 'dig3' and plotting slp*10.