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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).
Grib Definition Mode
Output
Specifies the output format you want. Specify one of the geopoints formats (Geographical Points, Geographical Polar Vectors or Geographical X Y Vectors).
Parameter
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
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If set to User, the output grid will be a regular lat/lon matrix defined by the parameters Area and Grid; if set to Grib, an example GRIB file should be specified by the parameter Template Grib.
Area
Specifies a geographical area over which to carry out the interpolation, the default being for the whole globe. Enter coordinates (lat/lon) of an area separated by a "/" (top left lat and lon, bottom right lat and lon); alternatively, use the assist button to define the area graphically. Only available if Grib Definition Mode is User.
Grid
Specifies a resolution in degrees, thus together with Area, determining the limits and density of the regular grid for interpolation of the point data values. Enter the longitude and latitude resolution as numbers separated by a "/". Only available if Grib Definition Mode is User.
Template Grib Definition
Specifies a GRIB file on which to base the output GRIB. The resulting GRIB field will be a copy of the template, with the values and parameter identifier modified.
Tolerance
Specifies a neighbourhood in degrees around each grid point. All geopoints data within this neighbourhood are used to interpolate the value at the central grid point. E.g. if Tolerance is 2 then all geopoints within a +/-2 degrees square around the grid point are used.
If your geopoints data has high spatial density then you can afford to specify a short neighbourhood, if the density is sparse you should use a wide neighbourhood. Remember that the wider the neighbourhood the smoother the resulting interpolated field (and the slower the computation).
Interpolation Method
Specifies how the values of the geopoints with in the window around a resulting grid point will be combined to produce the resulting value. The available algorithms are:
- Reciprocal: the values are weighted by the inverse of their distance from the target point. If one of the geopoints lies exactly on the target point then its value is used.
- Exponential mean:
- Exponential sum: