[ncl-talk] diagonal cross section with wrf_user_intrp3d

[Alexander Schaefer]

Hi Matt,

I haven't been able to get the diagonal slicing with wrf_user_intrp3d to
work right but I have been able to get diagonal cross-sections, though it
was not pretty.  Essentially created some arrays of the points that were in
the cross-section and then used wrf_interp_1d to interpolate the data at
each point in the list to higher resolution in the vertical. Works best
with points on the 45 deg angle to reduce horizontal space between points
but I suppose that any array of points should work.  I played with the
"2-point" example for multiple days before going other routes.  This way
does however let you control the horizontal extent like you were looking to
do.


I'll search for the script and pass it along if you would like to give it a
whirl.

-Alex

On Mon, Mar 23, 2015 at 11:40 AM, Matthew Fearon <Matthew.Fearon at dri.edu>
wrote:

>  Hi Evelyn,
> Thank you for your help. I was able to get a diagonal slice using the
> single pivot point (and angle) example. Still no luck with the two point
> example. The latter would be better as I could limit the horizontal extent
> more easily. I'll try again later.
> thanks again,
> Matt
>
>  ------------------------------
> *From:* Evelyn Grell - NOAA Affiliate [evelyn.grell at noaa.gov]
> *Sent:* Monday, March 23, 2015 8:12 AM
> *To:* Matthew Fearon
> *Cc:* wrf-help at ucar.edu; ncl-talk at ucar.edu
> *Subject:* Re: [ncl-talk] diagonal cross section with wrf_user_intrp3d
>
>         Matthew,
>
>  Regarding your second question (the easier one), I got confused by this
> too.  I believe the order of the variables got changed between versions:
>  In v6.1.2, the order to specify 2 points for a cross section has to be
> x1,x2,y1,y2.
> In v6.2.1, the order to specify 2 points has to be x1,y1,x2,y2.
> (maybe wrfhelp could add a note in the example.)
>
>  You can check by looking at the code in your
>  $NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl
>
>  Another thing that I ran into is that it assumes you are defining your
> points in "WRF" space (ie arrays start with 1) rather than in "NCL" space
> (ie arrays start with 0) so it subtracts 1 for you...
>
>  In wrf_user_interp3d:
>
> ; set vertical cross section
>      if (opts) then
>        xy = wrf_user_set_xy( z, loc_param(0)-1, loc_param(2)-1, \    ; the -1 is for NCL dimensions
>                                 loc_param(1)-1, loc_param(3)-1, \
>                                 angle, opts )
>
> (loc_param is the variable containing your XS endpoints).
>
>  About your first question, maybe you are missing the 2d interpolation
> that defines the x-axis?
>
>            something like:
>      if (xang.gt.20. .and. xang.lt.340) then
>        X_plane = wrf_user_intrp2d(lon,xspts,0.,True)
>      else
>        X_plane = wrf_user_intrp2d(lat,xspts,0.,True)
>      end if
>      dimsX = dimsizes(X_plane)
>      xspan = dimsX(0)-1
>
>       res at tmXBValues              = fspan(0,xspan,2)
>
>  Hope that helps,
> Evelyn Grell
>
>
> On Mon, Mar 23, 2015 at 12:21 AM, Matthew Fearon <Matthew.Fearon at dri.edu>
> wrote:
>
>>  Dear WRF-help and NCL users,
>>
>> Has anyone successfully plotted a cross section with wrf data
>> along a diagonal, say southeast to northwest or vice versa, using
>> wrf_user_intrp3d? North/south or east/west works fine, but from the
>> documentation, a diagonal seemed possible using the example below
>> *, *although I can't get it working
>>
>> *? *Also, the plane is defined (/xstart,xend , ystart,yend/) for sure
>> rather than (/xstart,ystart , xend,yend/) instead?
>>
>> thanks,
>> Matt
>>
>>
>>
>>
>> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
>>   load "$NCARG_ROOT/lib/ncarg/nclscripts/wrf/WRFUserARW.ncl"*
>>
>>   a = addfile <https://www.ncl.ucar.edu/Document/Functions/Built-in/addfile.shtml>*("wrfout_d01_2000-01-24_12:00:00.nc","r")
>>
>>   time = 1
>>   tc = *wrf_user_getvar* <https://www.ncl.ucar.edu/Document/Functions/WRF_arw/wrf_user_getvar.shtml>(a,"tc",time)   ; T [C]
>>   z  = *wrf_user_getvar* <https://www.ncl.ucar.edu/Document/Functions/WRF_arw/wrf_user_getvar.shtml>(a,"z",time)    ; z on mass points
>>
>>   plane = (/  40,81 , 259,81  /) ; approx. START x;y and END x;y point
>>
>>   ; Extract cross section from point A to point B, as defined in "plane"
>>   ; And vertically interpolate to height coordinates ("z")
>>   tc_plane = *wrf_user_intrp3d*(tc,z,"v",plane,0.,True)
>>
>>
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