Is the definition of the frequency range the same in both models (coarse and fine)?

What is the depth, in the coarse grid, along the boundary where you are extracting the spectra for the nested grid? and What is the depth at the boundaries in the nested grid?

Can be that the depth in the coarse grid along the boundaries, where the spectra is extracted, is deeper that in the nested grid in the same locations, and if the depth along the boundaries in the fine grid is shallow then most of the energy in the low frequencies is cut it.

What is the depth where the measurements were taken and what is the depth at that location according to the model?

"The energy spectrum seems to be shifted toward higher resolution when comparing to field measurements" . Do you mean toward higher frequencies?

Hi Thomas,

What is the directional resolution you use in your SWAN discretization for swell?

If you scroll down to the last three paragraphs on directional space:

http://swanmodel.sourceforge.net/online_doc/swanuse/node11.html

You will see that for swell, a directional resolution of 2 degrees or less may be required, for swell with a directional spreading of less than 10 degrees.

Heng

http://swanmodel.sourceforge.net/online_doc/swanuse/node11.html

I apologize for the delayed responses.

@Roberto Padilla-Hernandez: The depth is in fact shallower in the coarse grid at the spectra output location when comparing to the same exact output location of the nested grid. The offset is only about 20 cm. The average depth from the nested resolution is 95 cm and the output depth from the coarse grid is 75 cm.

I think the error has something to do with the BOUNDNEST1 command defining the input spectra for the nested run from the coarse grid results.

@Chai Heng Lim The directional resolution I use  for both coarse and nested runs is 10° or an [mdc] value equal to 36. Should I lower this number to get a resolution of 2°? For both nested and coarse runs? 

Thank you all so much for the input.

Thomas,

So have you tried with the 2° directional resolution? Are you able to capture the swell energy? 

Heng

Hi Tomas, indeed the resolution in direction is important and 10 is a very coarse directional resolution (you has need to increase the resolution on the nested grid) but, if you are dealing with depths of less than 1m we should not expect swell at those depths. Firstly, what is the periods (peak or mean) for the swell in the coarse grid? secondly, what is the direction of that swell? Is the direction of the swell coming into the estuary along the main axis of the estuary?

The setup of NESTout and BOUNDnest1 is very straight forward, unless you made a very bad mistake, swan would have indicated the error. 

@Chai Heng Lim Yes, that was a very good suggestion that I had not previously considered.  Unfortunately, the swell was still not picked up in that trial run.

@Roberto Padilla-Hernandez: I agree the swell energy will be minimal in that shallow of depths. However, the wave gauges we deployed at the study site are showing that there are instances in the time period that swell energy is present and sometimes even dominating the energy spectrum.

The swell at the offshore boundary condition containing the swell energy comes from the USACE Wave Information Studies. Offshore, the period ranges from 4 -11 s with an average of 6-7 sec. The direction is primarily 0° +/- 45°. Inside the bay, the swell is reduced to 5 sec. The swell energy does enter along the main axis as it refracts around the barrier islands.