[ncl-talk] Missing data in ERA5?

[Anne Seidenglanz]

The data has been closely examined. The problem was related to downloading
ERA5 data, for some reason a dimension "expver" (presumably experiment
version?) appeared in the variable. This dimension did not appear after a
fresh download of the data (minor changes in the script but the exact
reason remains obscure to me).
In any case, if someone happens to have problems plotting ERA5 data, pls
check if the dimension "expver" appears, and if necessary re-download the
data to end up with e.g. z(time, lev, lat, lon).

On Mon, Feb 8, 2021 at 8:38 PM Dennis Shea <shea at ucar.edu> wrote:

> The 'golden rule' of data processing is to look at the data.
>
> netcdf geop_500_975_89_20 {
> dimensions:
>         longitude = 1440 ;
>         latitude = 721 ;                * ; has pole points*
>         level = 2 ;
>         expver = 2 ;                      *; not sure what this is BUT,
> possibly, two different physics packages*
>                                                  *; OR, possibly, an
> ensemble of size two  OR, ???*
>         time = 160 ;
> variables:
>         float longitude(longitude) ;
>                 longitude:units = "degrees_east" ;
>                 longitude:long_name = "longitude" ;
>         float latitude(latitude) ;
>                 latitude:units = "degrees_north" ;
>                 latitude:long_name = "latitude" ;
>         int level(level) ;
>                 level:units = "millibars" ;
>                 level:long_name = "pressure_level" ;
>         int expver(expver) ;
>                 expver:long_name = "expver" ;
>         int time(time) ;
>                 time:units = "hours since 1900-01-01 00:00:00.0" ;
>                 time:long_name = "time" ;
>                 time:calendar = "gregorian" ;
>         *short z(time, expver, level, latitude, longitude)* ;     <======
> rank 5
>
> *                z:scale_factor = 0.898208868468462          ; netCDF CF
> [and COARDS] conventions*                *z:add_offset = 28656.6907881439
> *;             *; scale_factor and add_offet must be present*
>                 *z:_FillValue = -32767s ;
> ; CF                    *
>                 z:missing_value = -32767s ;                          ;
> COARDS
>                 z:units = "m**2 s**-2" ;
> ; COARDS and CF conventions
>                 z:long_name = "Geopotential" ;                     ;
> COARDS convention
>                 z:standard_name = "geopotential" ;              ; CF
> convention
>
> ======================================================
>
> dir="/Users/nuovoaccount/Documents/PYTHON/"
> fil ="geop_500_975_89_20.nc"
> f  = addfile(dir+fil,"r")
> z = *short2flt*
> <http://www.ncl.ucar.edu/Document/Functions/Contributed/short2flt.shtml>
> (f->z)
> printVarSummary(z)    ;  *(time, expver, level, latitude, longitude)*
> printMinMax(z,0)
>
> ---
> or,
>     [a] noting that NCL* eliminates degenerate dimensions* [size 1]
>     [b] no information is lost, since NCL will add variable attributes for
> the degenerate dimensions: *expver, level*
>
> z = *short2flt*
> <http://www.ncl.ucar.edu/Document/Functions/Contributed/short2flt.shtml>(
> f->z(:,1,1,:,:) )    ; second ensemble member and second level
> printVarSummary(z)    ; *(time, latitude, longitude) *with attributes *level
> *and* expver*
> printMinMax(z,0)
>
> HTH
>
>
> On Mon, Feb 8, 2021 at 8:46 AM Anne Seidenglanz via ncl-talk <
> ncl-talk at mailman.ucar.edu> wrote:
>
>> Hi,
>>
>> I am not new to NCL but encounter a rather new problem when dealing with
>> ERA5 data (in .nc format, see script attached). I am trying to produce a
>> simple test plot for geopotential height, and somehow all my data seems to
>> be missing? The error message appears:
>> warning:ContourPlotInitialize: no valid values in scalar field;
>> ContourPlot not possible:[errno=1101]
>> When I printed a subset of the dataset, all the values seemed to be
>> missing values.
>>
>> I have:
>> - tested that not all data is missing in Z with "print("Is Z all missing
>> ? " + all(ismissing(Z)))". It gave me False.
>> - I have tried both, reading in the data using "short2flt" to account for
>> scale factor and offset value, and without short2flt. In both cases appears
>> the missing value problem and the same error message.
>>
>> Where have I gone wrong?
>>
>> Thx for any help
>> Anne
>> _______________________________________________
>> ncl-talk mailing list
>> ncl-talk at mailman.ucar.edu
>> List instructions, subscriber options, unsubscribe:
>> https://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.ucar.edu/pipermail/ncl-talk/attachments/20210209/43cd2493/attachment.html>