[ncl-talk] hovmoller diagrams for vectors

[David Brown]

Hi Qi,
I am guessing you need to set vcMapDirection to False. This needs to be set
when you plot vectors with axes with coordinates that are not geographic.
 -dave


On Thu, Jul 23, 2015 at 4:01 AM, LI Qi <liqi123sh at qq.com> wrote:

> Hi Adam,
>
> Thank you very much! The example is very helpful! I use the function
> "overlay" to superimpose vectors over contours.
>
> However, the vectors seem different with the one I plot using GrADS (see
> below), and I don't know why. Could you help me look at my script? One more
> question is, how to reverse the X-Y coordinates?
> Attached is the data if it is needed.
>
> Much appreciated and best regards,
> Qi
>
> ncl plot:
>
> my script:
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/contrib/time_axis_labels.ncl"
> ;************************************************
> begin
> ;************************************************
> ; variable and file handling
> ;************************************************
>   in  = addfile("erai-qvint-zonmean.nc","r")
>   qu  = in->quz(:,:,0)
>   qv  = in->qvz(:,:,0)
>   qdiv  = in->qflxdiv(:,:,0)
>   time  = in->time
>   lat = in->lat
>
> ;************************************************
> ; plotting
> ;************************************************
>   wks  = gsn_open_wks("eps","eri-qhov")                ; Opens a eps file
>   ;gsn_define_colormap(wks,"WhiteBlueGreenYellowRed")             ; choose
> colormap
>
>   res           = True
>   res at gsnDraw   = False
>   res at gsnFrame  = False
> ;
> ; Set up some contour resources.
> ;
> ; Turn on contour fill, and turn other things off.
> ;
>   res at cnFillOn             = True
>   res at cnLinesOn            = False
>   res at cnInfoLabelOn        = False
>
> ;
> ; Define contour levels and their colors.
> ;
>   ;cnres at cnLevelSelectionMode = "ManualLevels"
>   ;cnres at cnMinLevelValF       = 980.0
>   ;cnres at cnMaxLevelValF       = 1040.0
>   ;cnres at cnLevelSpacingF      = 5.0
>   ;cnres at cnFillPalette        = "StepSeq25"   ; assign color map to
> contours
>
>
>   res at trYReverse           = True ; time from top to bottom, small to big
> ; Set special resources for the time axis
>   resTick                = True
>   resTick at ttmFormat      = "%d %c" ; form like "1 Jun", %d means day, %c
> means calendar
>   resTick at ttmAxis        = "YL" ; Y axis, Left
>
> ; Set resources necessary to customize Y axis labels
>   time_axis_labels( time,  res, resTick )
>
>   vecres                  = True            ; vector only resources
>   vecres at gsnDraw   = False
>   vecres at gsnFrame  = False
>   vecres at vcRefMagnitudeF  = 600000              ; define vector ref mag
>   vecres at vcRefAnnoOrthogonalPosF = -.535    ; move ref vector into plot
>
>   cnid = gsn_csm_contour(wks,qdiv,res)
>   vcid = gsn_csm_vector(wks,qu,qv,vecres)
>   overlay(cnid,vcid)
>   maximize_output(wks,True)
> end
>
>
> ------------------ Original ------------------
> *From: * "Adam Phillips";<asphilli at ucar.edu>;
> *Date: * Tue, Jul 21, 2015 04:02 AM
> *To: * "LI Qi"<liqi123sh at qq.com>;
> *Cc: * "ncl-talk"<ncl-talk at ucar.edu>;
> *Subject: * Re: [ncl-talk] hovmoller diagrams for vectors
>
> Hi Qi,
> I believe you will want to use the gsn_csm_vector_scalar plotting
> function. For an example showing how this function is used see example #6
> here:
> http://www.ncl.ucar.edu/Applications/overlay.shtml#ex6
> (see the overlay_6_new.ncl script)
>
> This example does not show a latitude/time plot but gsn_csm_vector_scalar
> should still work for your needs.
>
> Hope that helps. If not or if you have further questions please respond to
> ncl-talk.
> Adam
>
>
> On Sat, Jul 18, 2015 at 7:29 PM, LI Qi <liqi123sh at qq.com> wrote:
>
>> Dear NCL community,
>>
>> I would like to create latitude vs. time plot for moisture flux in
>> vectors.
>> But the function gsn_csm_lat_time seems to be used for scalar fieids.
>>
>> The data I have contains (qu,qv) over a limited area.
>> Below is a figure I plotted using GrADS for reference. How could I plot
>> it using NCL?
>>
>> Any suggestion would be much appreciated!
>>
>> Best,
>> Qi
>>
>>
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>
>
> --
> Adam Phillips
> Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
> www.cgd.ucar.edu/staff/asphilli/   303-497-1726
>
> <http://www.cgd.ucar.edu/staff/asphilli>
>
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