Re: [ferret_users] masking area

[Jaison Kurian <jaison@xxxxxxxxxxxxxxxxxx>]

Hi,
    If the mask variable "bv" is not having "any" time points, there
should not be any problem while multiplying "bv" with "rain". In this
case the show data command for "bv" should show empty Z and T axes as
follows:

 name   title                     I         J     K       L
 BV     Basin Mask              1:180     1:90   ...     ...

Suppose you have one time point for the variable bv, for L=1, there
will be a warning message as follows :

  "*** NOTE: Ambiguous coordinates on T axis: RAIN[D=1]*BV[D=2]"

This can be ignored. But from the second time point onwards the 
"rain*bw" will start complining as :

 **ERROR: illegal limits: BV is not in the range L=2
          Axis extremes are L=1

In this case you have to specify L=1 while multipling with rain
..like

   let rain_basin = rain[d=1] * bv[d=2,l=1]
  
This will fix the problem.

If these tips doesnot help you, please send me the output of 
"show data" command for those two datasets along with the error
messages (& multiplication line from the Ferret script).

Regards,

Jaison 


On Tue, 22 Aug 2006, DELCLAUX Francois wrote:

> Hi Ferret users,
> I would like to compute  spatial and temporal average rainfall on a 
> watershed.
> The watershed is  a  (x,y) netcdf file (variable bv) (0 outside the 
> basin, 1 inside the basin)
> Rainfall field is a (x,y,t) netcdf file, (variable rain) with same 
> spatial resolution as watershed.
> So I have supposed that mutiplying rain by bv, I would get a rainfall 
> field inside the wathershed.
> But Ferret does not accept to multiply a (x,y) variable by a (x,y,t) 
> variable.
> 
> In ferret documentation, masking  areas are defined from 3d fields, so 
> multiplication
> are possible. But not in my case.
> 
> How can I do this quite simple operation ?
> 
> Thanks in advance.
>