Versions Compared

Old Version 2

changes.mady.by.user Iain Russell

Saved on

compared with

New Version 3

changes.mady.by.user Fernando Ii

Saved on

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.
Section
Column
width76px

Column

This icon derives (and returns) a vertical cross section data unit of upper air fields along a specified arbitrary transect line. For each upper air field, point values are interpolated along the transect line, with a spacing consistent with the resolution of the input GRIB data.

The cross section data can be plotted or saved as a NetCDF data file.

A related icon, Cross Section View is used to provide cross section plotting specifications. You can use it to visualise a cross-section without explicitly deriving the cross-section data - see The View Concept in Visualisation.

The macro language equivalent is mcross_sect().

The Cross Section Data Editor

Data

Drop any icon containing or returning BUFR data. This may be, for example, a MARS Retrieval (of observations) icon, a BUFR file icon or an Observation Filter icon (provided it outputs BUFR, not geopoints).

Output

Specifies the output format you want. Specify one of the geopoints formats (Geographical Points, Geographical Polar Vectors or Geographical X Y Vectors).

Parameter

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 vertical axis of the plot in pressure levels rather than model levels when visualising the output.

Interpolate Values

Specifies whether to interpolate vertically the cross-section values into a regular set of interpolated vertical levels. Choosing not to interpolate returns a cross section data matrix with values at the original levels.

Note - if you need to use the cross section data in calculations further down the stream you should not interpolate.

Line

 To specify a parameter enter its unique BUFR descriptor value (a numerical code). Geographical Polar Vectors and Geographical X Y Vectors require two descriptors, separated by a slash (/). The descriptor value is of the form XXYYY, where XX defines the class (e.g. 12 = Temperature class) and YYY the parameter within that class (e.g. 12004 = Dry bulb Temperature at 2m). These descriptor values are different from the ones of the GRIB format. If you do not know the descriptor value, click-left on the assist button to obtain a check list of parameters and associated descriptors. This list only contains the most common parameters. If the one you need is not on the list you can use the BUFR Examiner (right-click, Examine the BUFR file) to see what is there, or up its descriptor value in the "BUFR Reference Manual" (available from http://www.ecmwf.int/products/data/software/bufr.html#description) - see "BUFR Table B", pages 6-19. The significance of code and flag values for non-quantitative parameters are given in the same manual, in "BUFR code table", pages 22-70.

Missing Data

If set to Ignore, missing data is not included in the output file; this is the default behaviour. If set to Include, missing data will be output to the geopoints file, its value being set to that specified by Missing Data Value. Note that when the output format is one of the two geopoints vector formats, the observation is considered missing if one or both of the parameters are missing.

...