3B2-GRIB API filter习题解答.pdf

Slide 1 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 1 Practicals 1 Change the date to 20090210 and the step to step 48 in the file tigge grib only for the data produced by ECMWF 2 Set the values of the first message in the file tigge grib to 1 2 3 4 5 6 3 7 and step to 72 Write only this message to the file practical2 grib Check the values coded with grib get data or grib dump 3 Append to practical2 grib all the messages containing the same parameter of the other centres encoded using a grid different than a reduced gaussian grid setting the step to 72 You can check if your filter is correct by comparing your output grib file with the sample in sample outputs grib filter your filter o out grib tigge grib grib compare out grib sample outputs practical1 out Slide 2 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 2 Practicals Extra 4 Split tigge grib into several files one for each centre containing only surface parameters and parameters that are in level 10 of height above ground For the surface parameters set changeDecimalPrecision to 2 and for the height above ground parameters set it to 3 Print information messages for each case such as Centre ammc parameter v not written Centre ammc parameter 10u written to practical4 ammc out 5 Merge the messages from the previously splitted grib files into a single file Write only messages encoded in a regular lat long grid and exclude messages for parameters 10u and 10v Slide 3 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 3 Solutions Find the solutions here ls l solutions total 20 rw r r x 1 trx ectrain 179 2013 02 25 16 18 practical1 filter rw r r x 1 trx ectrain 179 2013 02 25 16 18 practical2 filter rw r r x 1 trx ectrain 205 2013 02 25 16 18 practical3 filter rw r r x 1 trx ectrain 607 2013 02 25 16 18 practical4 filter rw r r x 1 trx ectrain 193 2013 02 25 16 18 practical5 filter Slide 4 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 4 Solutions Practical 1 solution grib filter practical1 filter tigge grib if centre is ecmf set dataDate 20090210 set step step 48 write practical1 out Slide 5 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 5 Solutions Practical 2 solution grib filter practical2 filter tigge grib if count 1 set step 72 set values 1 2 3 4 5 6 3 7 write practical2 out Slide 6 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 6 Solutions Practical 3 solution grib filter practical3 filter tigge grib if count 1 append practical2 out Slide 7 grib filter COM GRIB API ECMWF 26 Feb 01 Mar 2013 ECMWF Slide 7 Solutions Practical 4 solution grib filter practical4 filter tigge grib if typeOfLevel is surface typeOfLevel is heightAboveGround case heightAboveGround set changeDecimalPrecision 3 default print Unknown level type print Centre centre parameter shortName written to practical4 centre out write practical4 centre out else print Centre centre parameter shortName not written Slide 8 grib filt