This icon derives (and returns) a vertical average cross sectional data unit of upper air fields. For each upper air field, this average is taken along the North-South or East-West direction over a specified rectangular area and then interpolated horizontally along the direction perpendicular to the averaging direction with a spacing consistent with the resolution of the input GRIB data.
The average cross section data can be plotted (using a default visualisation and with the plot area based on the range of data values) or saved as a NetCDF data file.
A related icon, Average View, is used to provide average cross section plotting specifications. You can use it to visualise an average cross-section without explicitly deriving the average cross-section data - see Views..
The macro language equivalent is mxs_average().
The Average Data Editor
Data
Specifies the data (GRIB icon) from which to derive the average profile. The input GRIB icon must specify a multi-level (pressure or model levels) upper air meteorological variable, in a latitude-longitude or Gaussian grid. If the input data is specified in model levels, you must include the parameter LNSP should you want the vertical axis of the plot in pressure levels rather than model levels when visualising the output. Note that the input fields should be on the same grid. If more than one time and/or forecast step is contained in the GRIB icon, Average returns a set of average cross sections.
Interpolate Values
Specifies whether to interpolate vertically the average cross-section values into a regular set of interpolated vertical levels. Choosing not to interpolate returns an average cross section data matrix with values at the original levels.
Note - if you need to use the average cross section data in calculations further down the stream you should not interpolate.
Area
Specifies the coordinates of the area over which the average profile is calculated. Enter coordinates (lat/long) of an area separated by a "/" (top left lat and long, bottom right lat and long). Alternatively, use the coordinate assist button.
Direction
Specifies the direction along which the averaging of the variable is performed. Options are North South and East West. For North South, the averaging is weighted by cos(latitude).