Re: Error in Stream Function script - How to Overlay ?

Helen,

I think what you want is close to example 1 at:

    http://www.ncl.ucar.edu/Applications/conOncon.shtml

The data file (mxclim.nc) for this example can be found at:

    http://www.ncl.ucar.edu/Applications/Data/

In order for "overlay" to work correctly, both datasets that you are
plotting must be in the same (or close to the same) coordinate space.

That is, since we know that one of your datasets is in lat/lev space,
then the dataset that you overlay must also be in lat/lev space.

On Thu, 9 Jul 2009, Helen Parish wrote:

> Mary,
>
> After printing out values from the Fortran stream function routine I realised
> that the pressures are defined in the opposite sense in the NCL script and
> the Fortran routine. Now I have reversed them for the Fortran routine the
> plots appear more realistic. I had to (I believe correctly) reverse the
> direction of the pressure levels which are output from the Fortran routine
> before plotting the results (so that the surface pressure is at the bottom of
> the plot). What I want to do now is to:
>
> 1. Turn the stream function plots from colour contours to black and white
> contour lines with numbers on them, and
>
> 2. Overlay these black and white stream function contour lines on top of
> colour contour plots of, for example, "U" the zonal wind.
>
> I still want the overlaid plots to be a function of pressure/height and
> latitude, so I assume I will need to continue to use "gsn_csm_pres_hgt" ?. Do
> you know how I can do this ?. I enclose my current NCL script below.
>
> Thanks,
> Helen.
>
> Here is my current NCL script:
>
> external HELEN "./venus_mpsitest.so"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/contributed.ncl"
> begin
> ; input file
> diri = "./"
> fili = "zeusrand09125.cam2.h0.0172-01-05-00000.nc"
> fi = addfile (diri+fili, "r")
> ; output file
> diro = "./"
> filo = "helen.nc"
> system ("/bin/rm -f "+diro+filo) ; remove any pre-exist file
> fo = addfile (diro+filo, "c")
> ; add any file attributes
> fo_at_title = fi_at_title + ": Selected Variables at pressure levels"
> fo_at_history = systemfunc ("date")
> fo_at_source = fi_at_source
> fo_at_case = fi_at_case
> fo_at_Conventions = fi_at_Conventions
>
> Var = (/ "T" , "Q", "U", "V"/) ; select variable to be interpolated.
> nVar = dimsizes (Var)
> ; desired output levels
> lev_p = (/ 91500., 90000., 87500., 80000., 67500., 50000., 30000., 20000.,
> 10000., 5000., 3000., 1500., 750., 390., 200., 100., 50.,25., 14., 7., 3.5,
> 1.9, 0.95, 0.4, 0.1, 0.03 /)
> lev_p!0 = "lev_p" ; variable and dimension name the same
> lev_p&lev_p = lev_p ; create coordinate variable
> lev_p_at_long_name = "pressure" ; attach some attributes
> lev_p_at_units = "hPa"
> lev_p_at_positive = "down"
>
> hyam = fi->hyam ; read hybrid info
> hybm = fi->hybm
> PS = fi->PS
> P0mb = 0.01*fi->P0
>
> do n=0,nVar-1 ; loop over the variables
> X = fi->$Var(n)$
> Xp = vinth2p (X, hyam, hybm, lev_p ,PS, 1, P0mb, 2, True)
> copy_VarAtts(X, Xp)
> fo->$Var(n)$ = Xp ; write to netCDF file
> print (Var(n)+": interpolated and written to netCDF")
> end do
>
> end
> ;***********************
> ; zonal.ncl
> ;***********************
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
> load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
> ;***********************
> begin
> f = addfile ("helen.nc","r")
> print(f)
> v = f->V
> lat = f->lat
> printVarSummary( v )
>
> dimu = dimsizes( v )
> ntim = dimu(0)
> klvl = dimu(1)
> nlat = dimu(2)
> mlon = dimu(3)
>
> vavg = dim_avg_Wrap(v)
> vavgdouble = flt2dble(vavg)
>
> levpreverse = lev_p(25:0)
>
> vdouble = flt2dble(v)
> levpdouble = 100.0*flt2dble(levpreverse)
> psdouble = 100.0*flt2dble(PS)
>
> meridstream = new ( (/ntim,klvl,nlat/) , double)
> meridstream!0 = "time"
> meridstream!1 = "lev"
> meridstream!2 = "lat"
> meridstream&time = v&time
> meridstream&lev = levpreverse
> meridstream&lat = v&lat
>
> HELEN::VENUSDRV
> (mlon,nlat,klvl,ntim,vdouble,lat,levpdouble,psdouble,vavg@_FillValue,mer
> idstream)
>
> meridstream_reorder = meridstream(lev | :, lat | :, time | :) ;
> (lev,lat,time)
>
> ;***********************
> ; Create Plot
> ;***********************
> wks = gsn_open_wks ("pdf", "zeusrand.172.stream" ) ; open
> workstation
> gsn_define_colormap(wks,"rainbow") ; choose colormap
>
> res = True
> res_at_cnFillOn = True
> res_at_lbLabelAutoStride = True
> res_at_gsnMaximize = True ; if [ps, eps, pdf] make large
> res_at_gsnSpreadColors = True ; span color map
>
> nt = 0
>
> res_at_gsnCenterString = "zeusrand.172.stream"
> plot = gsn_csm_pres_hgt(wks, meridstream_reorder(:,:,nt), res ) ;
> (lev,lat,time)
>
> res_at_trYReverse = True
>
> end
>
>
>
>
>
>
> On Jul 8, 2009, at 8:38 AM, Mary Haley wrote:
>
>>
>> Helen,
>>
>> I think your new script looks okay. It doesn't make sense that
>> you have to attach the coordinate arrays before calling the Fortran
>> routine, but it also shouldn't hurt anything.
>>
>> If the plot is not making sense, maybe you have a missing value
>> set incorrectly?
>>
>> Make sure that the _FillValue attribute is set if there are
>> potential missing values in your data.
>>
>> --Mary
>>
>
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Received on Thu Jul 09 2009 - 13:37:17 MDT