Ocean Modeling Discussion

ROMS/TOMS

Search for:
It is currently Sun Aug 20, 2017 5:50 am




Post new topic Reply to topic  [ 2 posts ] 

All times are UTC

Author Message
PostPosted: Tue Nov 11, 2003 5:09 pm 
Offline

Joined: Fri Apr 25, 2003 9:22 pm
Posts: 119
Location: USGS
To create a better initialization field from our Adriatic CTD data, I was thinking about taking the OA'd field, and running the model forward for a couple of days with the observed (weak) wind forcing but strongly nudging back to the initial field along the sections of initial CTD data.

The reason is that while we had dense CTD coverage in the Northern Adriatic, we only cut through the mid and south adriatic pits with one detailed section each (sort of a "feature oriented") approach to sampling. So I though if we assimilate hard to these sections, the density structure from these sections will be advected by the geostrophic flow around the basins and come up with something more reasonable than that obtained by simply using OA.

But to assimilate strongest at the data sections seems to require setting the nudging coefs with short time scales at the CTD locations, and large time scales elsewhere. I thought I could set this in a NetCDF file, but it looks like right now it's only possible to do analytically in set_nudgcof.F.

Should I hack reading some file into set_nudgcof.F, or is there a better way?

Thanks, Rich

Richard P. Signell
signell@saclantc.nato.int


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Tue Nov 11, 2003 5:15 pm 
Offline
Site Admin
User avatar

Joined: Wed Feb 26, 2003 4:41 pm
Posts: 1008
Location: IMCS, Rutgers University
Actually, you can assimilate almost anything. It just depends on what assimilation scheme you use. By the way, we have been working for the last 5 weeks on the 4DVAR scheme for ROMS. Everything is code and seems to be working. We still need to make sure that the descent algorithm is correct. This was a very tricky thing to code. We are very happy with our progress. Now, we are working on the twin experiments.

You don't need to do nothing in "set_nudgcof.F". I'll use the OA error which is normalized by the field variance. This error then is nondimensional and a function of your data coverage and choice of spatial and temporal decorrelation scales. This error field is read in ROMS (see get_data.F) and converted to nudging time scales for assimilation via nudging. For instance, if you select a nudging scale of half a day, this scale will be associated with (1-error). That is, very strong nudging where there is data and no nudging where there is no data (when there is a large OA error).

Do this makes sense?

Good luck, H

Hernan G. Arango
arango@imcs.rutgers.edu


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group