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Interpretation of RMOL from WRF

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New member

I am doing some analysis related to atmospheric stability. And I understand WRF outputs RMOL, which represents atmospheric stability, with revision of Registry or Run-Time IO.
However, I can not understand the unit of RMOL from WRF. According to a description in Registry.EM_COMMON, it is a non-dimensional variable, although theoretically, it should be "m-1".

So, please kindly let me know which is a correct unit, and also how to convert from the non-dimensional RMOL into MOL.
Looking forward to hearing from you!


You are correct that the units are m-1. I agree that the description in the registry file is confusing.
Hi, kwerner.

Thank you for your reply. Well understood.
Based on my analysis, 1/RMOL multiplied by observation height, which is 10m in my case, seems more realistic than simple 1/RMOL, when compared to one calculated from a sonic observation by Eddy Covariance Method.
That is the reason why I checked the registry file and unit of RMOL. Then, I posted this topic here.

However, as you mentioned, if the registry is incorrect and unit of RMOL is truly inverse of [m], I need to find another cause of the difference...

Anyway, your answer is appreciated.

Hi, kwerner

I am still considering the possibility that the unit of RMOL from the WRF model is [-] rather than [m-1],
since a comparison with observation implies there is a big gap between the two.

Can you make sure that the hypothesis is not true?
Looking forward to hearing from you again.

Hi Shogo,
I apologize for the delay. I wanted to check with our physics expert, who said he's pretty sure it should be 1/L (we also have ZOL which is za/L where za is the lowest level).
Hi, kwerner,

Thank you for your support during your busy time. Well understood.
To ensure his comment, I will dig into the source code and find how those variables work shortly.
And then will get back to you.

Hi, kwerner

After a discussion with my colleagues, we found out that the inverse of MOL calculated from Ri has a good agreement with RMOL.
So, the unit should be [m-1].
Anyway, thank you for your support!