This icon is a plotting specification for cross section plots from a suitable GRIB data source . It can also take the output from a Cross Section Data icon as an input. In this case, a consistency check is performed between the parameters that are common to both icons.
In addition to the parameters required for the cross section computation, this icon specifies the axis details as well as the plot positioning in the plot frame of the display window / paper sheet and the overlay of different data units in the same plot.
To access the computed output values use the Cross Section Data icon.
If an orography is plotted it can be customised by applying a Graph Plotting visual definition icon.
Further details on the role and usage of View icons in the visualisation process, please see Views.
The macro language equivalent is mxsectview().
The Cross Section View Editor
Bottom Level
Specifies the lower limit of the cross section, as a pressure level (hPa) or model level (η levels).
Top Level
Specifies the upper limit of the cross section, as a pressure level (hPa) or model level (η levels).
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 Logarithmic.
Horizontal Axis
Specifies the plotting attributes of the horizontal axis. An Axis Plotting icon can be dropped here.
Vertical Axis
Specifies the plotting attributes of the vertical axis. An Axis Plotting icon can be dropped here.
Specifies the X offset of the plot from the left side of the plot frame (any subdivision of the display area). This is expressed as a percentage of the X-dimension of the plot frame. Specifies the Y offset of the plot from the bottom side of the plot frame (any subdivision of the display area). This is expressed as a percentage of the Y-dimension of the plot frame. Specifies the X length of the plot. This is expressed as a percentage of the X-dimension of the plot frame. Hence the sum of this X length plus the X offset cannot exceed 100 (it is advised that it does not exceed 95 since you need some margin on the right for things like axis or map grid labels). As above but for the Y length of the plot. Toggles the plotting of a border line around the plot frame On /Off . Comprising Page Frame Colour, Page Frame Line Style and Page Frame Thickness, these parameters specify the characteristics of the plot frame border line. Only available when Page Frame is On . Toggles the plotting of plot identification line On /Off . Specifies user text to be added to the plot identification line. Only available when Page Id Line is On . Toggles the plotting of a border line around the plot itself On /Off . In most cases you will want this to be left On . When Off the sides of the plot not equipped with axis will not be plotted. Comprising Subpage Frame Colour, Subpage Frame Line Style and Subpage Frame Thickness, these parameters specify the characteristics of the plot frame border line. Only available when Subpage Frame is On . Specifies the colour of the background of the plot (i.e. not affected by visual definitions like contour shadings or lines). Subpage X Position
Subpage Y Position
Subpage X Length
Subpage Y Length
Page Frame
Page Frame Parameters
Page Id Line
Page Id Line User Text
Subpage Frame
Subpage Frame Parameters
Subpage Background Colour