Bulk forcing of ROMS

ROMS-ites,

I have a question with regard to applying surface forcing to ROMS, which I hope one of you can help me with. I want to run an Indian Ocean domain forced with the GFDL-CORE 2 data set. I would rather not explicitly prescribe the SST and SSS in my model, so I intend to use this data set to apply bulk forcing across the domain (which CORE in its native state appears to accommodate well). However, I would like to weakly relax/nudge the derived SST and SSS values back to Levitus so I can restrict my tracer evolution somewhat. As yet, I don't seem to be able to find a way to do this. It seems that if I explicitly define the surface forcing through the make_forcing algorithm then I can activate the QCORRECTION and SFLX_CORR keys. However, defining bulk forcing negates this option.

Can anyone help me with this? Are there other, possibly better, alternate approaches?

Thanks

Ben

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Where to get high res bathymetry data for SA

Hi Schmodellers,

For those of you who might be interested in obtaining high resolution bathymetric data, I highly recommend you approach the Council of Geosciences; they are extremely helpful and resourceful. From what I have learned they are very keen on getting more involved with the universities and students.

The bathymetric data I received for False Bay was primarily fair chart derived so the density of the data varied throughout the domain, high data density was located in the bay and low density further offshore. The data needed to be gridded. In my case, as a result of the coarser resolution of the bathymetry further offshore, I had to grid the data into 100m cell sizes. See below, for a ‘zoomed in’ section of the end product compared with the GEBCO 1’ dataset.

The GEBCO 1’ dataset (Left) and the Council of Geosciences bathymetric data (right) gridded into 100m cells, both are overlaid with the 5m isobaths contours from 0-200m.

In particular you will notice that the GEBCO dataset excludes the features located at the mouth of the bay, namely Rocky Bank and Rough Bottom. From the ROMS simulations that I have run, first with a flat bottom and then with the high resolution bathymetry, the results have shown that these features significantly influence the circulation and thermal structure in the bay. They reduce the inflow of remotely forced circulation and furthermore act as a barrier reducing the amount of cold bottom water that enters the Bay. The results highlight the importance of using high resolution bathymetric data in this study.

If you are interested in getting bathymetric data or want to know more contact Michael Machutchon michael@geoscience.org.za from the Council of Geosciences. If you would like to see my code for gridding the data please don't hesitate to ask.

Welcome to the UCT ocean modelling blog!

This space has been created for modellers to, not only share their successes so that they can help and inspire others, but also to vent their frustrations so that they can let off steam (!) and, with a bit of luck, be helped by someone else. It is also a place where modellers can keep abreast of what the local community is up to...without leaving the comfort of their own office chair! I'm not trying to encourage social delinquency, but an online forum provides a more accessible way of sharing modelling activities with colleagues who may not be based in your immediate vicinity (like, in your office).

In the next few months a UCT ocean server protocol will be developed. This is becoming important as the number of people using Bart, Lisa, Marge and, in the near future, Maggie, increases. We are trying to develop a system that will help to make the administration and the upkeep of these machines more efficient. At the next Monday modellers meet (to be announced soon), we will talk about how we plan to use google applications to make our lives easier...and we look forward to your input on that.

As the first post, I thought some eye-candy would be nice...it's a ROMS model simulation of depth averaged currents, between 0-100 m depth for the Benguela system. The colourbar is the speed and the arrows show the direction: black for northward, white for southward. Sorry, the arrows are small and very difficult to see and if you maximize the animation, it is very blurry.