This icon derives (and returns) a Hovmøller diagram data unit along a specified arbitrary transect line or a rectangular area. This application can be used to display a two-dimensional graph with latitude or height as one axis and time as the other. If an input line is given, point values for each field are interpolated along the transect line, with a spacing consistent with the resolution of the input GRIB data. If a rectangular area is given, average values for each field are taken along the North-South or East-West direction.
The Hovmøller 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.
The option 'expand Hovmøller' allows the production of Hovmøller diagrams to be computed incrementally. This could be useful, for example, if the input data is too large or the Hovmoeller diagram needs to be updated periodically (e.g. to produce a diagram operationally during a certain period of time).
If access to the output computed values is not required, or for more control of the plotting, use the icon.Hovmoeller View.
The macro language equivalents are hovmoeller_area(), hovmoeller_line(), hovmoeller_height() and hovmoeller_expand() (depending on the Hovmøller type you specify).
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).