Re: masking of land data

["Yogesh K. Tiwari" <ktiwari@xxxxxxxxxxxxxxx>]

Hello Mick,

Thanks for the suggation, great !

It works.

But how to save the file if land data masked or 
ocean data masked.

Or I am thinking wrong ?

Actually I want to mask the data then save the 
files and then add all jan to dec files and then
make the time series of land or ocean mask.

But I am not sure I am thinking positive.

Can you help me to resolve this.

The script which worked for mask, looks like :-

use airs_jan.nc
!sh dat
use etopo20
shade/o/pal=grey if(rose ge 0) then 1
fill CO2[d=1];go land 7
shade/o/pal=grey if(rose ge 0) then 1
def grid/x=xlon/y=ylat grd
def grid/like=CO2[d=1] grd
let myrose=rose[d=2,g=grd]
shade/o/pal=black if(myrose ge 0)then 1
let land=if(myrose ge 0)then 1 else 0
let vland=if(land eq 1)then CO2[d=1]
fill vland

Many thsnks,

Regards,
Yogesh



Mick.Spillane@noaa.gov wrote:
> On Wed, 2 Mar 2005, Yogesh K. Tiwari wrote:
>
>
> > How to mask the land  data to see the monthly
> > variation(time series) at only ocean and vice versa.
>
> Hi Yogesh,
> 	What you need to do is to access one of the bathymetry files
> and use it to define a land/sea mask ON THE SAME GRID as your dataset.
> Try the following ... good luck,
> Mick
>
>
> !-------- demo of land/sea mask generation -----------
>
> ! FERRET SESSION 1 - make a fake dataset in a lat-lon region
> def axis/x=100e:160e:1/units=longitude xax
> def axis/y=50s:10s:1/units=latitude yax
> def grid/x=xax/y=yax grd
> let v=randu(x[g=grd]+y[g=grd])
> save/file=mydata.nc v
> quit                      ! end the ferret session
>
> ! FERRET SESSION 2
> ! 1) read in the datafile (with no mask of its own) ...
> use mydata.nc
> shade v
>
> ! 2) pick a bathymetry file (a bit finer than your data grid)
> use etopo20
>
> ! 3) see how it looks ...
> shade/o/pal=grey if(rose ge 0)then 1
>
> ! 4) give a name to the grid of the variable you want to examine
> def grid/like=v[d=1] grd
>
> ! 5) regrid "rose" to the grid of your variable and check it out
> let myrose=rose[d=2,g=grd]
> shade/o/pal=black if(myrose ge 0)then 1
>
> ! 6) define the mask and use it to define vland ...
> let land=if(myrose ge 0)then 1 else 0
> let vland=if(land eq 1)then v[d=1]
> shade vland
>
> ! 7) ... and vsea
> let vsea=if(land eq 0)then v[d=1]
> shade vsea

--

===========================================
Yogesh K. Tiwari,
Max-Planck Institute for Biogeochemistry,
Beutenberg Campus, Hans-Knoell-Strasse 10,
D-07745 Jena,
Germany

Office   : 0049 3641 576 376
Home     : 0049 3641 223 163
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e-mail   : yogesh.tiwari@bgc-jena.mpg.de
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