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Re: [ferret_users]plotting transect along the deepest depth (i.e thalweg)



Hi Murat,
          Two questions :
 
   1. What exactly is your problem? (Or what was the error message or
         difficulty that you have faced?)  

   2. While finding kzero, what the "I=1:`temperature,RETURN=iend`@max"
         stands for? If you intend to do the a similar operation on X 
         axis, you have to repeat all the steps for X-axis too. 

The example given in the webpage you have mentioned is working fine for
me. The procedure is explained step by step below :

  --->  let kvals = k[g=temp] + temp * 0

   This step will create a new variable "kvals", with following features 

       - XYZT grid will be EXACTLY same as that of "temp"
       - at each and every grid point, the value of kvals will be the
            level number (K-index) corresponding to the grid point
       - Missing values will be EXACTLY as in "temp"
   
   Example :   yes? use levitus_climatology
               yes? let kvals = k[g=temp] + temp * 0
               yes? list/x=80/y=10 temp, kvals

  ---> let kzero = kvals - kvals[k=1:`temp,return=kend`@MAX]

   This step will create a new variable kzero with following features
     
      - XYZT grid same as that of temp or kvals
      - will have zero value along Z-axis, ONLY at the deepest depth

   Example : After the lines in above above example, issue :

              yes? kzero = kvals - kvals[k=1:`temp,return=kend`@MAX]
              yes? list/x=80/y=10 temp, kvals, kzero

  ---> let integrand = temp * kzero[k=@WEQ:0]

    kzero[k=@WEQ:0] will return 1 if it finds a zero value exactly on
        a point along Z-axis, else it will return the "weights" to get
        zero, with missing values in all other Z-points. See User
        Manual, Ch3 Sec2.4.27.  @WEQ for details.

    Example : list/x=80/y=10 temp, kvals, kzero, kzero[k=@WEQ:0]

    When you multiply temp with kzero[k=@WEQ:0], the resulting variable
    will have valid data ONLY on those points where kzero[k=@WEQ:0] 
    have "non-misssing" values. Now it can be directly SUMMED to get
    the desired variable 

    Example :  yes? let integrand = temp * kzero[k=@WEQ:0]
               yes? plot integrand[k=@SUM,x=150]

Hope this helps,

Regards,

Jaison
          

On Tue, 19 Jun 2007, Murat Gunduz wrote:

> 
> Dear Ferret Users,
> 
> I would like to make a transect plot of temperature (from south to north)
> following the deepest depth from my 3D netcdf file.
> 
> I have searched the e-mail list, but I could not find any clue.
> I tried to modify the one of the script in FAQ, but without success
> http://ferret.wrc.noaa.gov/Ferret/FAQ/analysis/deepest_depth.html
> 
> 
> my simple script is below,
> 
> use temperature_3z.nc
> LET kvals = k[G=temperature] + 0*temperature
> let kzero = kvals - 
> kvals[K=1:`temperature,RETURN=kend`@MAX,I=1:`temperature,RETURN=iend`@max]
> LET integrand = TEMPERATURE* kzero[k=@WEQ:0]
> 
> 
> 
> Could you please help, how can I generate 2D transect along the thalweg?
> Thank you very much in advance.
> 
> Murat Gunduz
> 
> 
> 
> 
> 
> 
> 
> 
> 

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