Re: [ferret_users] coversion of model sigma coordinates

[Xavier Couvelard <xavier.couvelard@xxxxxxxxxxxxx>]

HI,
I think your problem is that zz must be a 3D var containing the depth 
(m) of each sigma layer at each horizontal grid point.

You can easily obtain those depth using zlevs.m in the Roms toolsbox, or 
you may managed to build it with ferret.

for me it work this is my script:

use zcoord.nc; !depth of sigma levels obtained with matlab
use roms_avg.nc; !roms avg file

def axis/z=0:4800:1/depth z100
let znew = z[gz=z100]

let zz=sigma_depth[d=1]*-1; !zlevs.m retrun negative depth

let temp_depth = ZAXREPLACE(temp,zz,znew)

fill temp_depth[i=150]

it Works!

Xavier
PHD student
IRD Noumea
New Caledonia


Steve Hankin a écrit :

> golla nageswararao wrote:
>
> > [...snip...]
> >   
>
>
> > I had used the following ferret script to convert the
> > sigma coordinates to depth coordinates.
> >
> > let bb= h + 0*temp[l=1]
> > let zz=(z+.03)*bb
> > def axis/z=0:4800:1/depth z100
> > let znew = z[gz=z100]
> > let temp_depth = ZAXREPLACE(temp,zz,znew)
> >
> >   I am getting correct vertical profile but the
> > problem is vertical resolution of my model is
> > irregular that is it uses more levels in upper ocean
> > than deep ocean.This makes me problem.   
>
> Hasty response here ... and assuming that I have understood your 
> problem correctly ...
>
> Your variable zz above can contain any list of Z coordinates.  For 
> example
>
> define axis/depth z100 = {0,100,200,500,1000,2000,4000}
>
> You can use "SHOW AXIS z100" to confirm your definition,
> and use DEFINE AXIS/EDGES if you want more precise control over the 
> boundaries between vertical grid cells.
>
>    - Steve
>
> >   I am enclosing the vertical profile plot with sigma
> > coordiantes and depth coordinates.
> >   U will notice that the curve is very much stretched
> > upto some 800m. or so due to more no. of levels in the
> > upper ocean.So what can I do with that to get correct
> > depth coordinates in the plot ? Please suggest me how
> > can I rectify my problem.
> > Any help is appreciated.
> > Thanks in advance.
> >
> > With regards,
> > G.NageswaraRao.
> >
> > From,
> >     G.Nageswara Rao,
> >   Research Scholar,
> >   INCOIS,
> >   Jeeidmetla,
> >   Hyderabad.
> >  
> >
> > Send free SMS to your Friends on Mobile from your Yahoo! Messenger. 
> > Download Now! http://messenger.yahoo.com/download.php
> >
> >