[ncl-talk] explicit contour colors not working

Fri Mar 10 14:16:34 MST 2017

Hi Mira,

First, if you are truly using NCL V6.0.0, then I recommend upgrading
because this is pretty old. Also, the cnFillPalette resource was added in
NCL V6.1.0, so it doesn't surprise me if it's not working with NCL V6.0.0.

If you actually do have NCL V6.2.0 or later, then something is wrong,
because your script works for me with a few minor changes:

   - I don't have a SLP.mon.mean.nc file, but I have a similar one.

   - My pressure values are in mb, so I had to scale the contour levels
   accordingly.

   - I removed this line:

res at cnFillColors = (/ 23,30,36,41,45,-1,59,63,68,74/)  ; set the colors to
be used

Because you shouldn't need to do this since you are setting:

res at cnFillPalette = "BlWhRe"

NCL will automatically span the full color map, and you should get white in
the middle since you chose the contour levels correctly. See the attached
image.

If you want to upgrade your version of NCL, then I recommend downloading
NCL V6.4.0.  See our release notes and download page:

http://www.ncl.ucar.edu/current_release.shtml
http://www.ncl.ucar.edu/Download/

--Mary

On Fri, Mar 10, 2017 at 1:35 PM, MIRA BERDAHL <
mlosic at scarletmail.rutgers.edu> wrote:

> Hi All,
>
> I'm working with NCL v. 6.0.0.  I am trying to make a 3 panel plot, with
> filled contours.  However, when I try to set explicit colors for the third
> panel (I would like to do a Red-White-Blue theme, centered on a white
> zero), I cannot get the appropriate colors plotted.  I am using
> con_Lev_4.ncl as an example (http://www.ncl.ucar.edu/
> Applications/contourLev.shtml).
>
> I have also tried setting this to manual levels with a max, min and
> interval for the contours and using a prescribed color table, such as
> hotcold_18lev, but the colormap defaults to the same as the top two panels.
>
> I've copied my script here, and the output figure is attached.
> Does anyone have ideas on how to change this third panel so the colors are
> Red-White-Blue themed?
>
> Thanks,
> Mira
>
>
>
>
>
> 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/csm/shea_util.ncl"
> ;************************************************
> begin
> ;************************************************
> ; read in netCDF files
> ;************************************************
> a = addfile("SLP.mon.mean.nc","r") ; sea level pressure
>
> ;************************************************
> ; read in zonal [u] and meridional [v] moisture transport (water vapor)
> ;************************************************
>
> slp = a->PRMSL_GDS0_MSL_S123(1:648,:,:)
>
>
> ;***************************************************************
> ; geneerate a new longitude list that is monotonically increasing
> ;***************************************************************
> g0_lat_1 = a->g0_lat_1
> g0_lon_2 = a->g0_lon_2
> g0_lon_2 = where(g0_lon_2.gt.180, g0_lon_2-360, g0_lon_2); change it from
> 220to 30 to be -110 to 30
> g0_lon_2&g0_lon_2 = g0_lon_2
> printVarSummary(g0_lon_2)
>
> slp&g0_lon_2 = g0_lon_2 ; replace with 'correct' ordering
> slp&g0_lon_2 = g0_lon_2
>
> printVarSummary(slp)
>
>
> ; Calculate the seasonal averages.
> slpDJF = month_to_season(slp, "DJF")
>
> printVarSummary(slpDJF)
>
>
> ; this data starts at 1958 (this is index 0), so 1963=5, 1973=15 etc.
>
>
> slpDJF_lon_hi = slpDJF((/8,10,11,16,25,26,36,37,41,47/),:,:)
> slpDJF_lon_lo = slpDJF((/5,6,22,27,29,33,34,38,45,48/),:,:)
>
> slpAvgTime_hi = dim_avg_n_Wrap(slpDJF_lon_hi,0)
> slpAvgTime_lo = dim_avg_n_Wrap(slpDJF_lon_lo,0)
>
> printVarSummary(slpAvgTime_hi)
> printVarSummary(slpAvgTime_lo)
>
>
> ; sneaky way to copy metadata over first.
> diff_slp = slpAvgTime_hi;
> diff_slp = slpAvgTime_lo - slpAvgTime_hi
>
> printVarSummary(diff_slp)
>
>
> ;************************************************
> ; create plot
> ;************************************************
> wks = gsn_open_wks("ps","Panel_lon_SLP") ; open a ps file
> gsn_define_colormap(wks,"temp1")
>
> plot = new(3,graphic) ; create a plot array
>
> ;---- set common resources for all plots
> res = True
> res at gsnDraw = False ; dont draw
> res at gsnFrame = False ; dont advance frame
> res at cnInfoLabelOn = False ; trn off cn info label
> res at gsnAddCyclic = False ; has to do with wrapping the lonitude at 0/360
> res at cnFillPalette = "matlab_jet"
>
>
> ;;************************************************
> ;; Choose a subregion
> ;;************************************************
> res at mpMaxLatF = 90 ;maximum latitude
> res at mpMinLatF = 25 ;minimum latitude
> res at mpMaxLonF = 30 ; max lon
> res at mpMinLonF = -110 ; min lon
> res at mpOutlineBoundarySets = "National"
> res at mpOutlineOn = True ; turn map outline on
> res at mpOutlineDrawOrder = "PostDraw"
> res at mpFillOn = False ; turn map fill off
> res at cnFillOn = True ; turn on color fill
> res at cnLinesOn = False ; turn off contour lines
> res at lbOrientation = "Vertical" ; make labels vertical
> res at cnFillPalette = "BlWhRe"
> res at cnLevelSelectionMode = "ManualLevels" ; set manual contour levels
> res at cnMinLevelValF = 100000 ; set min contour level
> res at cnMaxLevelValF = 102400 ; set max countrou level
> res at cnLevelSpacingF = 400 ; set contour spacing
>
>
> plot(0) = gsn_csm_contour_map(wks,slpAvgTime_hi,res)
> plot(1) = gsn_csm_contour_map(wks,slpAvgTime_lo,res)
>
> delete(res at cnLevelSpacingF) ; delete resources before reseting
> res at cnLevelSelectionMode = "ExplicitLevels" ; set explicit contour levels
> res at cnLevels = (/ -900, -700., -500., -300., -100., 100., 300., 500.,
> 700., 900./) ; set levels
> res at cnFillColors = (/ 23,30,36,41,45,-1,59,63,68,74/)  ; set the colors
> to be used
>
> plot(2) = gsn_csm_contour_map(wks,diff_slp,res)
>
>
> ;************************************************
> ; create panel
> ;************************************************
> resP = False ; modify the panel plot
> resP at txString = "lon - SLP"
> gsn_panel(wks,(/plot/),(/3,1/),resP) ; now draw as one plot;
>
>
> end
>
>
>
>
>
>
>
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