Based on various questions from NWP users, here are some answers to FAQ regarding the Aeolus L2B BUFR format and its use:
- Why are there extra unexpanded descriptors in the BUFR compared to the WMO BUFR template?
These changes are indeed some modifications to the original published template. We found that the WMO approved template cannot store the satellite range for Aeolus because the decision was taken to go for a lower orbit (this happened after we designed the template). The 20xxxx descriptors modify the number of bits and the scaling so the numbers fit again. The only thing you need to do is allow the changed number of unexpanded descriptors in your code (63 in stead of 51). Actually, after expansion, the number of descriptors will be identical to the original template, i.e. it will be reduced to 51. You should not need any changed BUFR tables at all, since this is part of the official BUFR file format itself.
You should also know that we plan 2 more updates with the same method in our upcoming software version (to be released at roughly 3-4 months after launch, at the end of the Commissioning Phase). In that copy we will also modify the derivatives (dhlos_dT and dhlos_dp) for the Rayleigh channel (so adding another 8 20xxxx descriptors).
Since getting formal registration by WMO is a very lengthy process, and we may need other modifications that we do not yet foresee, we decided to not request any changes with WMO for the time being.