- Created by Paul Dando, last modified on Feb 02, 2019
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Solution to grib_dump practical
1. To view the keys available for GRIB1 and GRIB2 have a look at the parameter database at http://apps.ecmwf.int/codes/grib/
2. To use grib_dump to inspect the contents of file1.grib1:
% grib_dump file1.grib1
By using grib_dump on its own and with the various options, (-O, -a, etc), you should find:
• the message is encoded using GRIB edition 1 (editionNumber=1);
• it contains the 2 metre temperature field (shortName=2t, marsParam=167.128);
• the dataDate= 20110225, the dataTime=12 and the forecast step=12;
• the data is on a reduced Gaussian grid (typeOfGrid=reduced_gg) with N=128 (Nj=256);
Alternatively, with grib_dump inspect some templates in the “GRIB_SAMPLES_PATH” directory.
3. For the file file2.grib2
% grib_dump file1.grib2
By using grib_dump on its own and with various options, (-O, -a etc), you should find:
• the message is encoded using GRIB edition 2 - grib_edition=2;
• it contains the temperature field on a specified height of 2 m above ground (shortName=2t, paramId = 167, discipline = 0, parameterCategory = 0, parameterNumber = 0, typeOfFirstFixedSurface = 103);
• the dataDate=20110225, the dataTime=12 and the forecast step=12;
• the data is on a reduced Gaussian grid (typeOfGrid=reduced_gg) with N=128 (Nj=256);
4. To quickly find the maximum, minimum and average values of the field, look for the computed keys max, min, and average.
For both files you should find:
• maximum = 314.204
• minimum = 222.44
• average = 285.261
Solution to grib_ls practical
1. To list the GRIB messages in msl.grib1
% grib_ls msl.grib1edition centre typeOfLevel level dataDate stepRange dataType shortName packingType gridType1 ecmf surface 0 20110225 0 cf msl grid_simple regular_gg1 ecmf surface 0 20110225 6 cf msl grid_simple regular_gg1 ecmf surface 0 20110225 12 cf msl grid_simple regular_gg1 ecmf surface 0 20110225 18 cf msl grid_simple regular_gg1 ecmf surface 0 20110225 24 cf msl grid_simple regular_gg5 of 5 grib messages in msl.grib1
The file contains mean sea-level pressure (shortName=msl) from the ECMWF EPS control forecast (dataType=cf) for 6-hourly steps from 0 to 24 hours for dataDate=20110225. The messages are encoded in GRIB edition 1.
2. To list the GRIB messages in msl.grib2% grib_ls msl.grib2edition centre date dataType gridType stepRange typeOfLevel level shortName packingType2 ecmf 20110225 cf regular_gg 0 meanSea 0 msl grid_simple2 ecmf 20110225 cf regular_gg 6 meanSea 0 msl grid_simple2 ecmf 20110225 cf regular_gg 12 meanSea 0 msl grid_simple2 ecmf 20110225 cf regular_gg 18 meanSea 0 msl grid_simple2 ecmf 20110225 cf regular_gg 24 meanSea 0 msl grid_simple5 of 5 grib messages in msl.grib2
The file also contains mean sea-level pressure (shortName=msl) from the ECMWF EPS control forecast (dataType=cf) for 6-hourly steps from 0 to 24 hours for dataDate=20110225. In this file the messages are encoded in GRIB edition 2.
The lists show the default keys printed by grib_ls for GRIB 1 and GRIB 2.
3. To print the mars keys, use grib_ls -m:% grib_ls -m msl.grib1
msl.grib1
domain levtype date time step param class type stream expver _leg_number
g sfc 20110225 0000 0 151.128 od cf enfo 0001 1
g sfc 20110225 0000 6 151.128 od cf enfo 0001 1
g sfc 20110225 0000 12 151.128 od cf enfo 0001 1
g sfc 20110225 0000 18 151.128 od cf enfo 0001 1
g sfc 20110225 0000 24 151.128 od cf enfo 0001 1
5 of 5 messages in msl.grib1
5 of 5 total messages in 1 files
% grib_ls -m msl.grib2
msl.grib2
domain date time expver class type stream _leg_number step levtype param
g 20110225 0000 0001 od cf enfo 1 0 sfc 151 g 20110225 0000 0001 od cf enfo 1 6 sfc 151 g 20110225 0000 0001 od cf enfo 1 12 sfc 151 g 20110225 0000 0001 od cf enfo 1 18 sfc 151 g 20110225 0000 0001 od cf enfo 1 24 sfc 151
5 of 5 messages in msl.grib2
5 of 5 total messages in 1 files
4. Output can be printed in descending step order using grib_ls with the -B option. Note it is necessary to use “step:i” here as step has a default type of ‘string’. % grib_ls -B "step:i desc" msl.grib1 edition centre typeOfLevel level dataDate stepRange dataType shortName packingType gridType 1 ecmf surface 0 20110225 24 cf msl grid_simple regular_gg 1 ecmf surface 0 20110225 18 cf msl grid_simple regular_gg 1 ecmf surface 0 20110225 12 cf msl grid_simple regular_gg 1 ecmf surface 0 20110225 6 cf msl grid_simple regular_gg 1 ecmf surface 0 20110225 0 cf msl grid_simple regular_gg % grib_ls -B "step:i desc" msl.grib2 edition centre date dataType gridType stepRange typeOfLevel level shortName packingType 2 ecmf 20110225 cf regular_gg 24 meanSea 0 msl grid_simple 2 ecmf 20110225 cf regular_gg 18 meanSea 0 msl grid_simple 2 ecmf 20110225 cf regular_gg 12 meanSea 0 msl grid_simple 2 ecmf 20110225 cf regular_gg 6 meanSea 0 msl grid_simple 2 ecmf 20110225 cf regular_gg 0 meanSea 0 msl grid_simple
5. To specify a set of keys to print, use the -p option: % grib_ls -p centre,dataDate,stepRange,typeOfLevel,shortName msl.grib1centre dataDate stepRange typeOfLevel shortNameecmf 20110225 0 surface mslecmf 20110225 6 surface mslecmf 20110225 12 surface mslecmf 20110225 18 surface mslecmf 20110225 24 surface msl5 of 5 grib messages in msl.grib1
Using the "key:i" for centre and levelType prints these keys as their integer values rather than strings: % grib_ls -p centre:i,dataDate,stepRange,levelType:i,shortName,paramId msl.grib1centre dataDate stepRange levelType shortName paramId98 20110225 0 1 msl 15198 20110225 6 1 msl 15198 20110225 12 1 msl 15198 20110225 18 1 msl 15198 20110225 24 1 msl 1515 of 5 grib messages in msl.grib1
Similarly for msl.grib2: % grib_ls -p centre:i,dataDate,stepRange,levelType:i,shortName,paramId msl.grib2centre dataDate stepRange levelType shortName paramId98 20110225 0 101 msl 15198 20110225 6 101 msl 15198 20110225 12 101 msl 15198 20110225 18 101 msl 15198 20110225 24 101 msl 1515 of 5 grib messages in msl.grib2
Solution to grib_ls -l practical
1. To list the nearest points to ECMWF (Lat 51.42 N, Lon 0.95 W) use % grib_ls -l 51.42,-0.95 msl.grib1 … 5 of 5 total grib messages in 1 files Input Point: latitude=51.42 longitude=-0.95 Grid Point chosen #3 index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) Other grid Points - 1 - index=17599 latitude=50.72 longitude=359.10 distance=77.54 (Km) - 2 - index=17598 latitude=50.72 longitude=358.20 distance=97.59 (Km) - 3 - index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) - 4 - index=17198 latitude=51.62 longitude=358.20 distance=62.87 (Km)
Note we specify the longitude of 0.95 W with -0.95 !
The nearest grid point is at latitude=51.62 longitude=359.10 (=0.9 W) and is 22.57 km from ECMWF.
2. To output only the forecast step and MSLP value at the nearest grid point use:% grib_ls -l 51.42,-0.95,1 -p stepRange msl.grib1 stepRange value 0 102527 6 102365 12 102456 18 102289 24 101862 5 of 5 grib messages in msl.grib1 Input Point: latitude=51.42 longitude=-0.95 Grid Point chosen #3 index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) Other grid Points - 1 - index=17599 latitude=50.72 longitude=359.10 distance=77.54 (Km) - 2 - index=17598 latitude=50.72 longitude=358.20 distance=97.59 (Km) - 3 - index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) - 4 - index=17198 latitude=51.62 longitude=358.20 distance=62.87 (Km)
Note it is necessary to specify MODE=1 in order to print the value of the nearest grid point only.
To output the values at the four grid points nearest to ECMWF, use MODE=4 which is the default:% grib_ls -l 51.42,-0.95 -p stepRange msl.grib1 stepRange value1 value2 value3 value4 0 102674 102663 102527 102501 6 102532 102516 102365 102333 12 102633 102585 102456 102426 18 102444 102390 102289 102259 24 102057 101959 101862 101760 5 of 5 grib messages in msl.grib1 Input Point: latitude=51.42 longitude=-0.95 Grid Point chosen #3 index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) Other grid Points - 1 - index=17599 latitude=50.72 longitude=359.10 distance=77.54 (Km) - 2 - index=17598 latitude=50.72 longitude=358.20 distance=97.59 (Km) - 3 - index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) - 4 - index=17198 latitude=51.62 longitude=358.20 distance=62.87 (Km)
3. To specify the land-sea mask, use:% grib_ls -l 51.42,-0.95,1,lsm.grib1 -p stepRange msl.grib1stepRange value0 1025276 10236512 10245618 10228924 1018625 of 5 grib messages in msl.grib1Input Point: latitude=51.42 longitude=-0.95Grid Point chosen #3 index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km)Mask values:- 1 - index=17599 latitude=50.72 longitude=359.10 distance=77.54 (Km) value=0.00- 2 - index=17598 latitude=50.72 longitude=358.20 distance=97.59 (Km) value=1.00- 3 - index=17199 latitude=51.62 longitude=359.10 distance=22.57 (Km) value=1.00- 4 - index=17198 latitude=51.62 longitude=358.20 distance=62.87 (Km) value=1.00
Here the mask value at the end of the line showing the four nearest grid points indicates which are land points: Land points have mask ≥ 0.5; sea points have mask<0.5.
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