[ncl-talk] Missing data in ERA5?

[Dennis Shea]

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
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