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Temperature Initialization of Spawned Nest in V4.0

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New member
I manage several operational systems that use FDDA observation nudging on d01 for the first 3 hours of simulation, then a 1-way d02 nest is spawned within it at the end of that period. With 4.0, the temperature grid is wonky in the initial d02 history output corresponding to the spawn time. The domain is spawed by interpolating from the main nest, and all the other variables seem OK. Basically the temperature is about 80C too cold (compared to the operational 3.9.1 run) at the top of the atmosphere. The cold bias decreases as you near the ground, with the lowest layers only being about 2-5K colder than the operational version. I have doubled checked the namelist.output from both the operational 3.9 and the test 4.0 run to make sure nothing else was changed or overlooked.

Anybody else running a configuration where a nest gets spawned like this?

Brent Shaw
This appears to be the []same issue addressed by Dave Gill[/url] to be in 4.0.2. I discovered that T (perturbation theta) is 0 in d02 at the initial time due to a registry error. Also explains why the model didn't blow up because it was purely an output issue, not something wrong with the T data itself. Note that I am running with use_theta_m=0, so the bug is independent of that setting. Just involves one minor change to Registry.EM_COMMON.
Hi Brent,
Thank you for letting us know that you figured this out. I'm glad it was an easy resolution!