[ncl-talk] Wrong with overlaying wind vectors on contour plots (X-axis is Longtitude and Y-axis is Pressue(Height))

Zhu CE lovingzhuce at 163.com
Tue Jul 11 21:09:03 MDT 2017

Yes, I meant  to plot UGRD and WGRD in gsn_csm_vector call.

The reason why I multiplied the return value of omega_to_w by 10 is the W is so small and I wanted to make W equaled to U so the wind vectors looked normally.

However, when I try to set res at vcMapDirection = False, everthing seems OK.  

Are there any mistakes I had done in those attemps? Please tell me, thanks a lot.

At 2017-07-10 21:05:51, "Mary Haley" <haley at ucar.edu> wrote:

Did you mean to plot UGRD and WGRD in your gsn_csm_vector call? If so, the issue may be either with your data or "omega_to_w".

Why are you multiplying the return value of omega_to_w by 10?

    WGRD = omega_to_w(VVEL_P0,pres,TMP_P0(10:30,:,:))*10

Please read the documentation for omega_to_w closely to make sure you are inputting the correct parameters with the correct expected units:


If you look the code for "omega_to_w", which is in $NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl, the calculation is simply:

   RGAS = 287.058            ; J/(kg-K) => m2/(s2 K)                    GRAV = 9.80665            ; m/s2                                    rho  = p/(RGAS*t)         ; density => kg/m3                        w    = -omega/(rho*GRAV)  ; array operation  

If you continue to have problems, please back to ncl-talk.

Thank you,


On Fri, Jul 7, 2017 at 11:16 PM, Zhu CE <lovingzhuce at 163.com> wrote:

Hi everyone,

I am trying to draw plots which overlay wind vectors on contour plots.

Here, the X-axis is Longtitude and Y-axis is Pressue(Height).

When I used wplot1 = gsn_csm_vector(wks,UGRD(:,232,:),WGRD(:,232,:),resV) and overlay(plot1,wplot1) to draw plot, a wrong figure I have gotten, only U-wind was drawn and no W-wind was drawn.

What did I do wrong? Could you help me? Thanks a lot.

P.S. Attachments are NCL script and the wrong figure.



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