[ncl-talk] impact of missing values

[Dennis Shea]

A simple illustration. No missing values; then one missing value.

%> ncl raster_test.ncl

Run the script twice:

(1) default; res at cnRasterSmoothingOn = False
(2) Turn on raster smoothing: res at cnRasterSmoothingOn = True

HTH
D

On Thu, Sep 27, 2018 at 10:46 AM Adam Phillips <asphilli at ucar.edu> wrote:

> Hi Laura,
> I don't believe you received an answer to your question. You asked whether
> setting cnFillMode = "RasterFill" will change the number of grid cells that
> are filled when there is missing data. The answer is yes. When you set
> cnFillMode = "RasterFill", every grid cell that is not set to _FillValue
> will be filled. When cnFillMode = "AreaFill" (the default), NCL will look
> at the values of the neighboring grid cells when shading the center grid
> cell. If not enough neighboring grid cells have data then NCL will not fill
> the center grid cell. Thus, if you want to color fill all valid grid cells
> you should set cnFillMode = "RasterFill".
> Adam
>
> On Thu, Sep 20, 2018 at 2:22 PM Laura Fowler <laura at ucar.edu> wrote:
>
>> Hello:
>>
>> I am trying to plot the index level of the cloud base of shallow
>> convection for one time step. In my netCDF file, there is no convection
>> when the index level is equal to 55 (which is the total number of layers in
>> my experiments).
>>
>> First, I plot the incidence of shallow convection defined as equal to 1.
>> when the cloud base is defined, and 0. otherwise (see kbcon_inc.pdf). Then,
>> I plot the actual value of the index level after defining the grid-point as
>> a missing value if the cloud base is equal to 55 (see kbcon.pdf). Missing
>> values are plotted in gray.
>>
>> When I compare the two plots, some grid-points are missing in kbcon.pdf
>> compared to kbcon_inc.pdf, as for instance over the tropical Pacific Ocean.
>> I know that the incidence filed is correct after comparing it against an
>> other diagnostics. I do not understand the differences between the 2 plots
>> and why some grid cell are missing. It it the impact of missing values. Is
>> it the impact of setting res at cnFillMode = "RasterFill"?
>>
>> If interested, the ncl script test.ncl is in
>>
>>
>> /gpfs/fs1/work/laura/MPASprojects2018/MPAS.cu_shallow.diagnostics/run3.40962.cu_gf/temp
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> --
>>
>> !-------------------------------------------------------------------------------------------------------------
>> Laura D. Fowler
>>
>> Mesoscale and Microscale Meteorology Division (MMM)
>> National Center for Atmospheric Research
>> P.O. Box 3000, Boulder CO 80307-3000
>>
>> e-mail: laura at ucar.edu
>> phone: 303-497-1628
>>
>>
>> !-------------------------------------------------------------------------------------------------------------
>> _______________________________________________
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>>
>
>
> --
> Adam Phillips
> Associate Scientist,  Climate and Global Dynamics Laboratory, NCAR
> www.cgd.ucar.edu/staff/asphilli/   303-497-1726
>
> <http://www.cgd.ucar.edu/staff/asphilli>
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