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Note for this parameter, the key "indicatorOfTypeOfLevel" is 112 i.e., which means "Layer between two depths below land surface" (See https://apps.ecmwf.int/codes/grib/format/grib1/level/3/) Code Table 3).
In this case, we allocate octet 11 for the "topLevel" key and octet 12 for the "bottomLevel" key.
However since the bottomLevel key is only one octet it cannot accommodate a value larger than 255! Therefore it is not possible to encode levels larger than that value in GRIB1 so we simply set all the bits to 1 (which means MISSING).
Here is a snippet from grib_dump:
| Code Block |
|---|
... ====================== SECTION_1 ( length=52, padding=0 ) ====================== 1-3 section1Length = 52 4 table2Version = 128 5 centre = 98 [European Centre for Medium-Range Weather Forecasts (common/c-1.table) ] 6 generatingProcessIdentifier = 152 7 gridDefinition = 255 8 section1Flags = 128 [10000000 (grib1/1.table) ] 9 indicatorOfParameter = 236 [Soil temperature level 4 (K) (grib1/2.98.128.table) ] 10 indicatorOfTypeOfLevel = 112 [Layer between two depths below land surface - depth of upper surface, depth of lower surface (cm) (grib1/local/ecmf/3.table , grib1/3.table) ] 11 topLevel = 100 12 bottomLevel = MISSING ... |
GRIB edition 2 addresses this shortcoming.
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