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Average Data Editor
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Specifies the data (GRIB icon) from which to derive the cross-section 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 a 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.
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Area
Specifies the coordinates of a transect line along the area over which the cross-section average profile is calculated. Enter coordinates (lat/long) of a line an area separated by a "/" (easternmost top left lat and long, westernmost bottom right lat and long); alternatively. Alternatively, use the coordinate assist button (see "Geography help tool" in "Editor Window Help Tools" on page XXX).
Note that it is possible to define a line through either pole by describing the line’s coordinates as follows. First, when specifying the latitudes of the two points, imagine that the latitude values go above 90 when you cross the North Pole and below -90 when you cross the South Pole. Next, if you wish a straight line, ensure that the two longitude values are the same as each other. An example demonstrates this. Say you wanted to defined a straight-line cross-section from 60S/25E to 60S/155W. This would be specified as -60/25/-120/25. The fact that one of the latitude values is below -90 indicates to Metview that a cross-section going through the South Pole is desired. Once this has been established, the fact that the two longitude values are identical tells Metview to use a straight line through the pole. If this is the intent, then only one unique longitude value is required, as the other one can be deduced. Giving Metview two different longitude values will cause a cross-section consisting of two curves to be produced.
Wind Parallel
Setting this option to On will produce a cross section plot of the projection of the wind onto the cross section plane (going from a 3D wind field to a 2D wind field projection). This is plotted using wind arrows. Valid values are On/Off.
Wind Perpendicular
Setting this option to On will produce a cross section plot showing the projection of the horizontal wind components onto the direction perpendicular to the cross section plane. The result is a one-dimensional quantity and is plotted with contour lines. Also produced is another cross section plot of the W component of the wind. Valid values are On/Off.
Wind Intensity
Setting this option to On will produce a cross section plot of the scalar wind intensity, plotted with contour lines. If one of the previous two parameters is On, then the intensity is that of the specified projection. Also produced is another cross section plot of the W component of the wind. Valid values are On/Off.
Lnsp Param
Specifies the parameter number of the Lnsp data, if you are using non-ECMWF data - ECMWF uses specific parameter numbers different from the WMO ones. Enter whichever parameter number is appropriate for your data.
U Wind Param
Specifies the parameter number of the U wind component data, if you are using non-ECMWF data - ECMWF uses specific parameter numbers different from the WMO ones. Enter whichever parameter number is appropriate for your data.
V Wind Param
Specifies the parameter number of the V wind component data, if you are using non-ECMWF data - ECMWF uses specific parameter numbers different from the WMO ones. Enter whichever parameter number is appropriate for your data.
W Wind Param
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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).