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spec_bdy_width question

This post was from a previous version of the WRF&MPAS-A Support Forum. New replies have been disabled and if you have follow up questions related to this post, then please start a new thread from the forum home page.


I am trying to dampen boundary artifacts in my inner nest that are originating due to the fact that my one-way nest's southern boundary intersects with complex orographic features (it cannot be helped).

As such, I changed my spec_bdy_width from 5 to 10 points, increasing my relax zone from 4 to 7 and my spec_zone from 1 to 3. This helped a lot in reducing boundary artifacts that were quite intrusive to the nest's interior.

To understand what is happening, I ran an additional test in which spec_bdy_width = 10, but now spec_zone and relax_zone = 1 and 9 respectively. I got the exact same result as the previous experiment (relax_zone = 7, spec_zone = 3). This should not be the case with linear damping of the LBCs following Davies and Turner (1977), as the weights should be changed between the experiments. I am using wrfinput* files in ndown, which uses spec_bdy_width = 5, relax_zone = 4, and spec_zone = 1, but this shouldn't matter.


I would expect different results when the relax_zone and spec_zone are different in different experiments. I have no answer to your question at present. I will talk to ur expert and get back to you soon. Thanks for your patience.
HI Stefan,
It turns out that WRF ignores the relax and spec widths, and simply takes the total. It says total-1 = spec width, and the rest is relax. This explains the behavior.