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lateral sponge needed with open BCs

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New member

I have been using lateral open boundaries in version 3 of WRF.

I solved a problem related to reflection of gravity waves propagating horizontally. The waves reflect off the lateral open boundaries. (The "gravity-wave radiating" condition does not prevent this, even when I adjust the prescribed wave-speed to match that for the stability.)

The fix I found was to impose a sponge on the five grid-points nearest the open boundary (in pbl driver) with relaxation of potential temperature towards its average over the 25% of the domain along the boundary.

The spurious lines of cloud caused by standing waves now disappear. The fix works well.

I can contribute code if you are interested.

Would you please provide more information about this issue?
(1) Which version of WRF are you running?
(2) Which ideal case did you test that shows problems related to gravity wave reflection?
(3) Can you upload a few plots to illustrate the simulations with and without your fix?

Ming Chen