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Linear wave patterns in the radiation fields

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Hi all,

I'm running a WRF v4.1.3 configuration using ndown and finding some unusual wave-like patterns in the radiation fields. The current configuration is set up to produce domains at 25, 5, and 1 km horizontal resolution. The wave-like patterns are shown in the attached .png file for the 1 km horizontal resolution domains, particularly the eastern half of the second plot. The waves are not present in the 5 km horizontal resolution domain.

I've noticed these waves in several other ndown runs I've recently produced, too. In some cases, they are prevalent in ~50% of the outputted time-steps, and certainly seem unrealistic. What could be causing WRF to produce these patterns?

I've also attached the namelists.


EDIT: Turns out these wave patterns are also very noticeable in the wind fields.


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Hi Ty,

First, take a look at this post. The situation seems similar, though not exactly the same. It could be similar behavior you're seeing, though. A couple of questions:
1) are the stripes resolved before the end of the simulation?
2) Have you tried using diff_6th_opt = 2?
Hi Kwerner,

Indeed, I've run a few extra tests with diff_6th_opt=2 and a handful of different dynamics settings with no luck. The waves resolve before the end of the simulations, and in some cases are highly unrealistic. Some days the flow field begins to evolve in a realistic manner before developing into distinctive, linearly-spaced, boundary-parallel positive-negative strips.

Out of interest, I ran an exact simulation using a standard configuration of 25, 5, 1 km resolution but just turning feedback off (instead of using ndown for the 1 km domain) and it did not product the waves.

Could be an issue with ndown?

Hmm, that's interesting that it didn't have the issue when not using ndown. Out of curiosity, is it necessary for you to use ndown, as opposed to just turning off feedback? I know it is in many cases, but just making sure it wouldn't be easier (at least to get rid of this issue for you for now) to not use ndown.