Re: [ferret_users] Overlaying location of minimum U wind

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi-
I don't know why the locations would be wrong. I wonder if it could be 
be the order of operations, y=@loc:`minval`, and the averaging in Z?  
SET MODE DIAGNOSTIC might  help sort that out. You could try defining a 
variable first,

let uwndave = uwnd[z=`zl`:`zu`@ave]

and operate on that to see what difference it makes.

The reason that /LINE has no effect is that each PLOT command is drawing 
a separate single-point line, and has no knowledge of the points that 
came before.  You could save each location after it's computed, and plot 
at each X a 2-point line using {xpos,xlast}, {ypos,ylast}.

Ansley

On 2/4/2011 3:23 AM, Samrat Rao wrote:
> Hi,
>
> I am trying to locate and plot the minimum U wind values on a lat-lon 
> figure. I am attaching the figure generated.
>
> After ploting the U wind contours i use the following:
>
>  repeat/range=0:120:2/name=xpos (  \
>    let minval =  uwnd[x=`xpos`e,y=@min,z=`zl`:`zu`@ave,l=7]; \
>    let ypos = uwnd[x=`xpos`e,y=@loc:`minval`,z=`zl`:`zu`@ave,l=7]; \
>    list ypos; \
>    
> plot/line=14/color=red/thickness=3/size=0.15/symbol=3/vs/nolabel/overlay 
> xpos,ypos  )
>
> As you can see the symbols are being plotted below the location of 
> minimum U wind. I have the following questions:
>
> 1) The reason for the incorrect location of the symbols. I am not 
> having this problem with NCEP reanalysis data.
>
> 2) I am unable to get the 'line' qualifier connect the different 
> symbols. How to do this?
>
> 3) At some locations there is a discontinuity (for example around 
> 55E). To me it looks artificial.
>
> 4) In case there is a missing value for 'ypos', then how do i ensure 
> that this does not cause an error and abort in the script execution?
>
> I hope you people will have patience to reduce some of my difficulties.
>
> Thanks,
> Samrat Rao.