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A Product Definition Template Number of 8 means "deterministic and interval-based". And 11 means an interval-based ensemble member.
In the latter case the GRIB message will have the key "perturbationNumber" but not in the former case because it is not part of an ensemble.
For examples of instantaneous parameters see: Mean sea level pressure and 2 metre temperature. For an interval-based parameter see: Maximum temperature at 2 metres in the last 24 hours.
Now there are other kinds of product groups which follow this pattern. Let's look at the atmospheric chemical constituents:
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