Windstress discontinuities between inner and outer nest bdry

Discuss the nesting capability within the model itself and any problems you might have run into.

Windstress discontinuities between inner and outer nest bdry

Postby lmp4 » Fri May 25, 2018 11:58 am

I was wondering if have noticed slight wind stress discontinuities between inner (moving) and outer (static) WRF domains?

I'm actually using COAWST (coupled WRF/ROMS system) and this discontinuity is causing major issues near shallow areas of the coastline in ROMS. To be specific I'm running a coupled WRF/ROMS typhoon model system and have blow-ups consistently near the coast in ROMS as soon as the inner domain hits the coastline (vortex following). The very slight discontinuity is causing havoc for the ROMS zeta field :(

I know groups have done hurricane modelling with COAWST before (and likely to have inner and outer domains with vortex following) but I've found no information on the forums on how to possibly deal with the situation. I think this may be more of a WRF issue than a COAWST issue but usually people doing WRF only runs wouldn't care so much about these discontinuities since there are no feedback effects! So I think the issue is highly specific to the coupled nested environment.

Is there anything that can be done via the WRF side to smooth this inner/outer domain boundary? :?

As a test/fix we decided to create a 2km WRF/ 4km ROMS (single domain) coupled system (i.e. without any nesting) and ROMS runs smoothly without any issue in zeta or resulting blow-ups :)
However, I'm not sure how good of a fix this is for our long term goals since this drives up the cost of running the model significantly. Furthermore, I'm not too sure of the effect of downscaling the WRF bdy conditions from GFS (25km) to a 2km model domain! (very extreme downscaling...usually 1/3 is recommend but I'm actually not sure why...)

Any suggestions / thoughts would be greatly appreciated!
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