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This icon controls the parsing and plotting of an ASCII table file such as CSV - see ASCII Tables for more information. The columns used for plotting can be selected by name (if there is a header row) or by index, starting at 1. The points may be interpreted as either geographic co-ordinates or as generic X/Y co-ordinates.

The macro language equivalent is table_visualiser().

The Cross Section Data Editor

Data

Specifies the data (GRIB icon) from which to derive the cross-section 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 orography and the vertical axis of the plot in pressure levels rather than model levels when visualising the output.

This application also supports GRIB data with general height-based coordinates.

If wind arrows are to be plotted, then the input data should include three-dimensional wind data, i.e. the u/v/w wind components should all be present.

If more than one time and/or forecast step is contained in the GRIB icon, it returns a set of cross sections.

Line

Specifies the coordinates of a transect line along which the cross-section is calculated. Enter coordinates (lat/long) of a line separated by a "/" (easternmost lat and long, westernmost lat and long). Alternatively, use the coordinate assist button. 

The cross section is calculated from a set of geographical points taken along the input transect line. The point selection takes into consideration the resolution of the data and assures that a minimum of 64 points will be generated. Parameter Horizontal Point Mode selects the algorithm used to compute these points.

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

Specifies the parameter number of the W 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.

Horizontal Point Mode

Specifies how the geographical points along the input transect line will be computed. Valid values are Interpolate and Nearest Gridpoint. Setting this option to Interpolate will create a regular set of interpolated geographical points along the transect line. Setting this option to Nearest Gridpoint will instead select the nearest points from the data.

Vertical Coordinates

Setting this option to User will enable the use of general height-based coordinates. In this mode, additional GRIB fields should be supplied (one per model level) where the values of the grid points represent the heights of their locations. Valid values are Default and User.

Vertical Coordinate Param

Specifies the parameter number of the general height-based coordinates if Vertical Coordinates is set to User.

W Wind Scaling Factor Mode

Specifies the algorithm to compute the scaling factor for the vertical wind component. Valid values are Automatic and User. Setting this option to Automatic will compute a scaling factor taking into consideration the geographical area, the top/bottom pressure levels and the size of the plot window. Setting this option to User will apply a scaling factor defined by parameter W Wind Scaling Factor.

W Wind Scaling Factor

Specifies the vertical wind scaling factor if W Wind Scaling Factor Mode is set to User.

Level Selection Type

Specifies the method to define the output pressure levels when converting model level data to pressure levels. Options are:

  • From Data (default)
    • compute the absolute bottom pressure level from the data
    • for each model level, compute the average pressure along the cross section line and then use this mean pressure as the vertical pressure co-ordinate for that level
    • compute extra levels at the bottom by adding an offset (10 hPa) until it reaches the bottom pressure level, computed previously. This will avoid blank areas in the plot near the orography line.
  • Count
    • calculate the output pressure levels by taking into account the bottom and top pressure levels (Bottom Level and Top Level) and the given number of levels (Level Count). The computed levels will be evenly spaced on either a linear or a logarithmic scale depending on the value of Vertical Scaling.
  • Level List
    • use the given list of pressure levels (Level List)

Level List

Specifies a list of output pressure levels separated by a “/”. Only available if Level Selection Type is set to Level List.

Level Count

Specifies the number of output pressure levels if Level Selection Type is set to Count.

Vertical Scaling

Specifies the type of vertical axis - Linear or Log. Only available if Level Selection Type is set to Count.

Bottom Level

Specifies the lower limit of the cross section, i.e. the bottom pressure level (hPa). Only available if Level Selection Type is set to Count.

Top Level

Specifies the upper limit of the cross section, i.e. the top pressure level (hPa). Only available if Level Selection Type is set to Count.

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