This icon extracts values from complex BUFR messages where coordinate descriptors are required to locate particular data. Briefly, when a BUFR element descriptor described as F'XX'YYY has an F of 0 and an XX of less than 10, it is a 'coordinate descriptor', which means that it retains its current value until redefined. In this way, a set of observations 'inherit' the same value for such a descriptor without it appearing explicitly for each observation. The purpose of this icon is to extract data that can only be described by using coordinate descriptors; for more complete BUFR data extraction, it can be used with BUFR output from the Observation Filter icon. The output is a geopoints file.
The macro language equivalent is bufr_picker().
The Bufr Picker 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
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 BUFRDC Home) - 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.
Missing Data Value
Available only for Missing Data set to Include. Any missing observations will be output as this value (default 0). It is wise, therefore, to ensure that this value is outwith the range of possible values for the requested parameter(s)
Coordinate Descriptors
A list of coordinate descriptors separated by forward slashes, e.g. 5043/5042. The order in which the descriptors are specified is important – coordinates in a BUFR message are nested, and they must be listed from the outermost to the innermost. This parameter must be used in conjunction with the Coordinate Values parameter.
Coordinate Values
Provides a list of values corresponding to the Coordinate Descriptors list. For example, given the sample Coordinate Descriptors above, a list of values set to 3/14 would mean "extract the chosen parameter where the field of view number (5043) is 3 and channel number (5042) is 14". If the last (or only) value is ALL, then all values related to the innermost coordinate will be extracted.
Fail On Error
If set to Yes, then any error encountered when trying to decode the input data will result in the module failing (turn red and abort any dependent processes); if run inside a macro, the macro will also fail. If set to No, then any such errors will not be fatal, and an empty data file will be returned.