Resource: variable

The variable resource is used to specify the parameter or parameters to be plotted. This is done by specifying:

1. simple variables which are parameters taken directly form the input data file,
2. derived variables which are new parameters derived from the simple variables,
3. composite variables which are plots of several simple and/or derived variables.

Simple variables are determined by the input file and its list of parameters.  Derived and composite variables are determined through a function-like line either on the command line, the variable prompt or in the var file.  

The .var file is a list of the variables that can be specified and the appropriate commands to use to plot the data.  Each WXP program has it own .var file associated with it which is in the file_path directory.  The user can specify a different var file by using the following syntax:

   -va=fi:variable.var:variable

The "fi:" prefix specifies that the next parameter in the string is the name of the var file.  

There are several methods for specifying variables.  The simplest is to provide the alias as listed in the var file.  

   temp    Temperature         1  +temp    [F]

In this case, you would specify "temp".  This will plot the simple variable "temp".  Simple variables are specified by a "+" prefix.  From the var file, the default plot parameters are to plot the temperature in F (Fahrenheit).

To modify the units of a particular variable, just put the desired units after the variable separated by a colon ":".

Enter the variable: temp:C

The plot parameter information can be more extensive:

Enter the variable: temp:C:cf:in=5

In addition to changing the units, the plot type is set to color fill with a contour interval of 5.  

Hybrid variables can also by specifed for the variable resource:

Enter the variable: conv(wind)

which will compute the convergence of the real winds.  The value of wind is aliased in the var file to the U and V wind components specified as a vector quantity.  You can generate vector quantities with some functions:

Enter the variable: grad(temp)

This will compute the gradient of temperature.  Then by specifying a plot type of vectors, the vector field will be plotted.