Atmosphere forcing & coordinate convertion

[bibi951]

Hi everyone
I am preparing ROMS Atmosphere foring. And I quite confused about this:
1)Suppose I have interpolate data to the computing grid coordinate(xi,eta),and I have done the rotaion. But how about the scale factor during the coordinate transformation, I just see the rotation, lengh scale doesn't change ? DO I need to undef the CPP option CURVILINEAR to tell Roms what I have done during forcing preparation? If yes, how about the coordinate tranformation terms in the eq( xi ,eta)?
2) I don't do interpolation myself.I want to give the data and associated lon-lat, and let Roms do the work, so I need to give the data lon-lat information, what should lon-lat information look like in a CDL file?
Would someone please help me . Thanks

[kate]

I can answer question 2:

Code: Select all

netcdf uwind_4 {
dimensions:
        wind_time = UNLIMITED ; // (17540 currently)
        lat = 94 ;
        lon = 192 ;
variables:
        float Uwind(wind_time, lat, lon) ;
                Uwind:missing_value = -1.e+34f ;
                Uwind:_FillValue = -1.e+34f ;
                Uwind:long_name = "10m Uwind component" ;
                Uwind:units = "m/s" ;
                Uwind:coordinates = "lon lat" ;
        double lat(lat) ;
                lat:units = "degrees_north" ;
                lat:point_spacing = "uneven" ;
                lat:axis = "Y" ;
        double lon(lon) ;
                lon:units = "degrees_east" ;
                lon:modulo = 360. ;
                lon:point_spacing = "even" ;
                lon:axis = "X" ;
        double wind_time(wind_time) ;
                wind_time:units = "days since 1900-01-01 00:00:00" ;
                wind_time:axis = "T" ;
                wind_time:bounds = "TIME_bnds" ;
                wind_time:time_origin = "1-JAN-1958" ;
                wind_time:calendar = "LEAP" ;

// global attributes:

Actually, that time_origin is scary, but ROMS seems to be ignoring it.

[bibi951]

Hi,Kate
Thank you for your help.It is really kind of you.
I use it and I guess Roms does this work,and I don't have to worry about the Missing_Value problem?
The second question is about setting the initial condition.I think ROMS will take it as in the xi_eta_s coordinates.(ROMS will not do this work for me again, right?) So I have to do the 3D interpolation and rotation myself.I know that you take advantage of manu_toolbox.But it is really difficult for a new user.I notice that rnt_fill* will solve the filling_vallue problem,and rnt_oa* will do the interpolation(both using *mex.dll), I think they are the core codes for data preparation am I right? Is this what you exactly use? And what will Roms do if I have Fillvalue(1e37)?
Would you give me some guide to use this wonderful toolbox, just a clue would be appreciated?
Any advice would be appreciated!
Best regards!

[kate]

I use it and I guess Roms does this work,and I don't have to worry about the Missing_Value problem?

Do you have Missing_Values in your forcing fields? Mine are global.

The second question is about setting the initial condition.I think ROMS will take it as in the xi_eta_s coordinates.(ROMS will not do this work for me again, right?) So I have to do the 3D interpolation and rotation myself.I know that you take advantage of manu_toolbox.But it is really difficult for a new user.I notice that rnt_fill* will solve the filling_vallue problem,and rnt_oa* will do the interpolation(both using *mex.dll), I think they are the core codes for data preparation am I right? Is this what you exactly use? And what will Roms do if I have Fillvalue(1e37)?
Would you give me some guide to use this wonderful toolbox, just a clue would be appreciated?
Any advice would be appreciated!
Best regards!

We do use Manu's toolbox to create initial and boundary conditions. I have run those scripts, but not written them. Matlab has never been my favorite tool and I left Rutgers to avoid it (well, partly ). So my advice is to find someone who has used the same format of source file for your initial conditions and to bug them.

Manu has promised an updated toolbox but has been distracted by things like applying for tenure and having a second child. We are also hoping to come up with this functionality in Python.

[bibi951]

Hi,everyone
I took data from Ncep (2.5*2.5) and oaflux(1*1),And I wrote cdl file as Kate adviced.However I encounter this error
NLM: GET_STATE - Read state initial conditions, t = 0 00:00:00
(File: initial_lJ.nc, Rec=0001, Index=1)
..........................
GET_2DFLD - surface u-wind component, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_1.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 1.00000000E+35 Max = -1.00000000E+35)
GET_2DFLD - surface v-wind component, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_1.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 1.00000000E+35 Max = -1.00000000E+35)
GET_2DFLD - solar shortwave radiation flux, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_1.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 1.00000000E+35 Max = -1.00000000E+35)
GET_2DFLD - net longwave radiation flux, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_1.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 1.00000000E+35 Max = -1.00000000E+35)
GET_2DFLD - surface air pressure, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_1.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 1.00000000E+35 Max = -1.00000000E+35)
GET_2DFLD - surface air temperature, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_2.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = -5.33855130E+00 Max = 2.86994297E+01)
GET_2DFLD - surface air specific humidity, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_2.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 0.00000000E+00 Max = 2.06493227E+01)
GET_2DFLD - rain fall rate, t = 0 00:00:00
(Rec=0001, Index=1, File: frc_1.nc)
(Tmin= 0.0000 Tmax= 729.0000)
(Min = 1.00000000E+35 Max = -1.00000000E+35)

I have checked my netcdf file , they all have reasonable values? But why I get this here? (Min = 1.00000000E+35 Max = -1.00000000E+35)
See something wrong?
Besides,I use mpirun,how to set to idb?

I would very aprrecitate your suggestions.
Thanks .

[wilkin]

I have checked my netcdf file , they all have reasonable values? But why I get this here? (Min = 1.00000000E+35 Max = -1.00000000E+35)
See something wrong?

This is odd. At first glance I would have thought this indicated that you have some "missing" values (maybe over land?) in your netcdf file and on input to ROMS they have been assigned the value 1+35 because this is the netcdf file "_FillValue" or "missing_value" attribute.

However, notice that the MIN is 1+35 while the MAX is -1+35, i.e. MIN is > MAX. This suggests ROMS has not read any data to reset the default min/max values it starts with in the range check. I don't know whether this means all the data are missing values or that there is something else amiss.

It is likely that whatever tool you used to check your netcdf file automatically makes conversion from the fillvalue to a NaN and hence you think the values are all reasonable but they are not. You can usually disable this so you can see precisely the values stored.

You might want to check more carefully that your forcing files are indeed OK. For some variables you get sensible ranges, but for others you do not, so you have some inconsistency in what you're doing. Beware of scale_factor and add_offset attributes, and type inconsistencies (int,float,double) in the netcdf file.

[bibi951]

Thank you for your kind reply, wilkin.
I checked my netcdf,finally I found that my latitude orientation is wrong.
Now Roms reads the right data.
Thanks

[subbareddy]

hi sir,
can you tell, how to prepare initial condition and forcing file for the roms.
can you explain elobaratively ?
please help me
thank you

[stone]

Hi, all
I wonder whether I can just provide the atm forcing in a small domain(not global and not my grid), which just covers my grid domain, using this "lon:modulo = 360. ;" property just like a global forcing?
I did so (feeding with qnet,uvstess,eminusp), and ran ROMS, but find that the surface tempreture goes crazy warming. I use OAflux to provide qnet and checked the data,it looks good (like the origional data)
I doubt i have misused the "lon:modulo = 360. ;" property ,have I?
Thanks

[kate]

The lon:modulo = 360 is for global domains. What happens if you don't use the modulo attribute? You can take it away with NCO.

[stone]

Thanks for your advice, Kate
I remove the "modulo",tempreture is the same as it was.
I output the "shflux" (-150 ~ 150 W*m-2) and "ssflux"(-6e-6 ~ 2e-6) or swflux is -3 ~ 1 cm/day. It seems OK.
Then, I increase the horizontal(TNU2 1e2) and vertical background(AKT_BAK 1e-5) trace diffusion,not much change of the result.
Maybe this is now not in this topic ,Sorry for that.

[tasha]

(Min = 1.00000000E+35 Max = -1.00000000E+35)

I had the same problem with one of my netcdf forcing files from NCEP and (thanks to your post) I similarly fixed it by flipping my latitude values - and my data to match.

[tony1230]

hi kate
It's the first time i have seen 'modulo'. i have absolutely no
idea about the 'lon:modulo = 360'.would you explain to me what's
the equation mean or how to operate it!
Best regards!

tony

[kate]

Modulo would be useful for domains that span the globe, though I don't think ROMS now looks for it. For instance, an Arctic grid will have all longitudes from 0 to 360. Say your winds are every two degrees, starting at 1, going to 359. How do you interpolate those points at 359.8? You need to wrap that value from 1 degree over to seem like it's at 361.