How to make forcing?

[safoora.seddigh]

Hello all,
I have preparied the grid file for my region succesfully.
Now I want to make my forcing file but I don not know what should I do exactly?
I know that I have to use some scripts in matlab but I could you let me know how I can get started?
Thanks,
Safoora

[kate]

This topic is coming up a lot lately. You start by finding some forcing fields that you want to use with ROMS. Do you want to apply wind stress or do you want to have ROMS compute wind stress from winds (and other fields)? How much resolution in time and space do you need from your winds? What's available? I'm using a global atmospheric product and letting ROMS do the interpolation to the ROMS grid. Is that good enough for your needs? Maybe you can start there anyway and look for better winds while doing some exploratory runs.

[safoora.seddigh]

Hello Kate,



Sorry, it took me a while to know what I want. I am going to use data with Spatial Coverage of 2.5 degree latitude x 2.5 degree longitude global grid, and temporal coverage of 4-times daily for like 2 years(http://www.esrl.noaa.gov/psd/data/gridd ... rface.html).
I assume that ROMS should be used to calculate the wind stress.
However, I think your global atmospheric product could also help me to get started and to become more familiar with these kinds of data. So would you please let me know more about this product? Finally, could you give me more instructions on the next steps of making forcing files? Thank you.

[mathieudever]

Hello,

I also have a question relating to this topic. What if you have no forcing at all? My idealized model do not have winds, of heat fluxes or anything other forcings. What do I put as the input file then? because ROMS do not run if I do not include a forcing file:

Code: Select all

 READ_PHYPAR - could not find input file:  ocean_frc.nc

 Elapsed CPU time (seconds):


 ROMS/TOMS - Output NetCDF summary for Grid 01:

 ROMS/TOMS - I/O error ............... exit_flag:   4


 ERROR: I/O related problem.

Thank you or the help,
Mat

[kate]

Mat's question is easier - if you have no surface stress, you have to set it explicitly to zero, usually with ANA_SMFLUX. If it still complains, look to globaldefs.h to see if you can figure out which field it's missing.

For Safoora, download the netcdf files for surface air temperature, pressure, humidity, winds and rain. The product I use also has incoming shortwave and longwave radiations. You need to find out what height these things are at - is it 10 m above the surface or something else? Those numbers get set in ocean.in:

Code: Select all

! Height (m) of atmospheric measurements for Bulk fluxes parameterization.

      BLK_ZQ == 2.0d0                     ! air humidity
      BLK_ZT == 2.0d0                     ! air temperature
      BLK_ZW == 2.0d0                     ! winds

Next, use "ncdump -h" on one of those files and compare that to what's in the Data/ROMS/CDL//frc_bulk.cdl file. If necessary, you can use ncrename from the nco package to make things match. Then look at the times and make them match your calendar. Maybe someone here already has some scripts to do this?

[safoora.seddigh]

Dear Kate,
Thanks for your reply and help, but I am a little confused about the methods of making forcing file.
Would you please tell me about the differences between matlab scripts in matlab folder in ROMS and python scripting method in PYROMS in general and in particular case of forcing file?
Best regards,
Safoora

[kate]

I guess I was intentionally vague because you need to build up some tools for manipulating netcdf files that you are comfortable with. I used to use some horrible fortran codes, I then switched to primarily NCL and NCO for these things. I am slowly learning to use Python. Others use Ferret. These are all just means to an end and the endpoint is clear from the CDL files.