[ncl-talk] unexpected white contours in color filled plot

[Mark Branson]

Hello.

I'm running ncl v6.2.1 and here is what I'm doing in the attached script:

1) read in a long time series of zonal wind and surface pressure data from CAM output.
2) interpolate them to constant pressure levels using vinth2p.
3) compute long-term monthly means with clmMonTLLL.
4) compute the annual mean of the monthly means.
5) subtract off the annual mean from the monthly means.
6) select one latitude (the equator), and then take the mean of all longitudes.
6) make a color-filled height versus time cross section plot.

I get the plot (see attached), but some of the contours near the top are white.  I thought maybe it was because there were some missing or bogus values, so I inserted a check for those with the ismissing and isnan_ieee functions and it seems the data is fine.

Any ideas?

Thanks,
Mark Branson


begin
 a = addfile("/pool/mark/spcam_nlev51/spcam_nlev51.cam.h0.0003-01.nc","r")
 hyam = a->hyam
 hybm = a->hybm

 b = addfile("/pool/mark/spcam_nlev51/uandps.nc","r")
 u = b->U         ;u = [time | 338] x [lev | 53] x [lat | 96] x [lon | 144]
 ps = b->PS       ;ps = [time | 338] x [lat | 96] x [lon | 144]
 u at _FillValue = default_fillvalue("float")

 if (any(ismissing(u))) then
   print("### original u array contains some missing data ###")
 end if

; interpolation variables
 plvlM = (/ 30.,50.,70.,100.,150.,200.,250.,300.,350.,400.,450.,500.,550., \
           600.,650.,700.,750.,800.,850./)
 plvlM at units = "mb"
 nplvlM = dimsizes(plvlM)

 p0     = 1000.     ; mb required by vinth2p
 interp = 2         ; log interpolation
 extrap = False     ; no extrapolation past psfc.

 tmp = vinth2p(u,hyam,hybm,plvlM,ps,interp,p0,1,extrap)
 if (typeof(tmp).eq."double") then
   uwind1 = dble2flt(tmp)
 else
   uwind1 = tmp
 end if

; compute long-term monthly means
 uclm = clmMonTLLL(uwind1)       ;uclm = [month | 12] x [lev_p | 33] x [lat | 96] x [lon | 144]

; annual mean of monthly means
 uann = dim_avg_n_Wrap(uclm,0)   ;uann = [lev_p | 33] x [lat | 96] x [lon | 144]

; subtract off annual mean from monthly means
 do i = 0,11
   uclm(i,:,:,:) = (/ uclm(i,:,:,:) - uann(:,:,:) /)
 end do

 uwind2 = uclm(:,:,47,:)              ; select the equator for the latitude
 uwind3 = dim_avg_Wrap(uwind2)        ; mean of all longitudes
 uwind = uwind3(lev_p|:,month|:)      ; swap the array dimensions:  month,level --> level,month

 printMinMax(uwind,False)

 if (any(ismissing(uwind))) then
   print("### uwind array contains some missing data ###")
 end if
 if (any(isnan_ieee(uwind))) then
   print("### uwind array contains some NaNs ###")
 end if

 uwind at long_name = "SP-CAM, 51 levels, Monthly Means"

 wks   = gsn_open_wks ("eps", "test1")           ; send graphics to EPS file
 gsn_define_colormap(wks,"BlRe")

 res                      = True                  
 res at cnFillOn             = True                 
 res at cnLinesOn            = True                
 res at lbLabelBarOn         = True              
 res at cnInfoLabelOn        = False

; change labels for monthly mean plot
 res at tmXBMode = "Explicit"
 res at tmXBLabelFontHeightF = 0.015
 res at tmXBLabels=(/"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep", \
                  "Oct","Nov","Dec","Jan"/)
 res at tmXBValues = ispan(0,12,1)

 plot = gsn_csm_pres_hgt (wks,uwind,res) 
end

** OUTPUT FROM THE SCRIPT **

/Users/mark/mmf/SPCAM5/stratosphere_gwdrag/spcam_nlev51> ncl hvstime.ncl
Copyright (C) 1995-2014 - All Rights Reserved
University Corporation for Atmospheric Research
NCAR Command Language Version 6.2.1
The use of this software is governed by a License Agreement.
See http://www.ncl.ucar.edu/ <http://www.ncl.ucar.edu/> for more details.
(0)	min=-9.835   max=6.77056

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