[ncl-talk] contour map not showing colors

[Tabish Ansari]

Hi

I have a cropped dataset over northern China from the CAMS Reanalyses
product which contains 3-hourly PM2.5 concentrations for the year 2019.

Here's the variable metadata:
        short pm2p5(time, latitude, longitude) ;
                pm2p5:scale_factor = 7.76424835780384e-11 ;
                pm2p5:add_offset = 2.54403361691801e-06 ;
                pm2p5:_FillValue = -32767s ;
                pm2p5:missing_value = -32767s ;
                pm2p5:units = "kg m**-3" ;
                pm2p5:long_name = "Particulate matter d < 2.5 um" ;
                pm2p5:standard_name =
"mass_concentration_of_pm2p5_ambient_aerosol_particles_in_air" ;


I've written a fairly straightforward NCL script just to plot the annual
average PM2.5 concentration. It shows the map with contour lines and an
appropriately ranged labelbar but with no colors within the map.
Here's my script:
==============================================================================
begin

;SOURCING FILES
DIR = "/worknb/users/tans/Capstone-Maya/"
a   = addfile(DIR+"CAMSconc_3hourly_NCP2019.nc","r")


;READING DATA
pm25NCP = short2flt(a->pm2p5)
pm25NCP = pm25NCP * 10^9
pm25NCP = pm25NCP(:,::-1,:) ; flipping latitudes to correct the inverted
data


;PREPARING TIME-AVERAGED DATA
pm25NCPavg = dim_avg_n_Wrap(pm25NCP,0)
printVarSummary(pm25NCPavg)
printMinMax(pm25NCPavg,True)


;START THE GRAPHICS
wks = gsn_open_wks("x11","NCPavgconc")
res                     = True
res at gsnMaximize         = True           ; Maximize plot in frame
res at cnFillOn            = True           ; turn on color
;res at cnFillPalette       = "MPL_Reds"     ; set color map
res at cnLinesOn           = True           ; turn contour lines on/off
res at gsnAddCyclic        = False
res at mpFillOn            = True

;SELECT NCP REGION FROM THE GLOBE
res at mpProjection           = "Mercator"
res at mpLambertParallel1F    = 30.
res at mpLambertParallel2F    = 40.
res at mpLambertMeridianF     = 115.

res at mpLimitMode            = "Corners"          ; choose region of map
res at mpLeftCornerLatF       = 20.
res at mpLeftCornerLonF       = 100.
res at mpRightCornerLatF      = 50.
res at mpRightCornerLonF      = 130.

plot = gsn_csm_contour_map(wks, pm25NCPavg, res)

end
===================================================================


The output of the script is as follows:
 Copyright (C) 1995-2019 - All Rights Reserved
 University Corporation for Atmospheric Research
 NCAR Command Language Version 6.6.2
 The use of this software is governed by a License Agreement.
 See http://www.ncl.ucar.edu/ for more details.

Variable: pm25NCPavg
Type: float
Total Size: 6724 bytes
            1681 values
Number of Dimensions: 2
Dimensions and sizes:   [latitude | 41] x [longitude | 41]
Coordinates:
            latitude: [20..50]
            longitude: [100..130]
Number Of Attributes: 8
  _FillValue :  -32767
  units :       kg m**-3
  long_name :   Particulate matter d < 2.5 um
  standard_name :
mass_concentration_of_pm2p5_ambient_aerosol_particles_in_air
  _FillValue_original : -32767
  missing_value_original :      -32767
  missing_value :       -32767
  average_op_ncl :      dim_avg_n over dimension(s): time
(0)
(0)     Particulate matter d < 2.5 um (kg m**-3) : min=3.35468   max=205.552



And I have attached the resulting map as a png file.

I'd really appreciate it if someone can point out what is needed for the
plot to show the contour colors.

Thanks a lot.

best regards,

Tabish

--------------------------------------------------------------------------------------
Dr Tabish Ansari
Research Associate
Air Quality Modelling Group
Research Institute for Sustainability (RIFS) - Helmholtz Centre Potsdam
Potsdam, Germany
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