[ncl-talk] Trough Axis

[Dennis Shea]

There is no NCL function "to find out the position of the trough." This is
complicated. See:
   *Objective Identification of Trough Lines Using Gridded Wind Field Data*
<https://www.mdpi.com/2073-4433/8/7/121>
====
*http://www.ncl.ucar.edu/Applications/polyg.shtml*
<http://www.ncl.ucar.edu/Applications/polyg.shtml>

If **you** know the lat/lon locations

 res           = True                    ; plot mods desired
 res at gsnDraw   = False                   ; don't draw yet
 res at gsnFrame  = False                   ; don't advance yet

 res@ ... other resources

;---Resources for the polyline
 plres                  = True           ; polyline mods desired
 plres at gsLineThicknessF = 2.0            ; line thickness
 plres at gsLineColor      = "blue"         ; color of line

;************************************************
; create points for trough line
;************************************************
 lat_trough = (/ ...... /)  ; multiple points
 lon_trough = (/ ...... /)

 plot = gsn_csm_contour_map(wks,...,res)     ; create the create the
 trough_line = gsn_add_polyline(wks,plot, lon_trough ,lat_trough ,plres)
 draw(plot)
 frame(wks)


On Thu, Jan 9, 2020 at 10:40 PM Babitha George via ncl-talk <
ncl-talk at ucar.edu> wrote:

> Hai,
>
> I was trying to plot the axis of a trough or to find out the position of
> the trough in NCL. Can anyone direct me on this?
>
> Thanks in advance.
> Regards
> --
> Babitha George
> Research Scholar
> IIST, Valiamala
> Thiruvananthapuram
> +91 9656661855
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