[ncl-talk] hovmoller diagrams for vectors

[LI Qi]

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
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