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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, The following vertical coordinates are supported:
- pressure levels
- model levels (hybrid levels used by the IFS). In this case you must include
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- parameter LNSP (logarithm of surface pressure) should you want the orography and the vertical axis of the plot in pressure levels rather than model levels when visualising the output.
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- general
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- coordinates (defined by parameter Vertical 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.
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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. in lat1/lon1/lat2/lon2 format.
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.
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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 ecCodes paramId 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.LNSP data. The default value is 152 (as used by ECMWF).
U Wind Param
Specifies the parameter number ecCodes paramId 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.. The default value is 131 (as used by ECMWF).
V Wind Param
Specifies the parameter number ecCodes paramId 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.. The default value is 132 (as used by ECMWF).
W Wind Param
Specifies the parameter number ecCodes paramId of the W vertical 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.. The default value is 135 i.e. pressure velocity (as used by ECMWF).
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 andUser.
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 level) where the values of the grid points represent the heights of their locations. Valid values are Default andUser.The default value is Default.
Vertical Coordinate Param
Specifies the parameter number ecCodes paramId of the general height-based coordinates if Vertical Coordinates is set to User.
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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.