issues: 146908323

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
146908323 MDU6SXNzdWUxNDY5MDgzMjM= 821 datetime units interpretation wrong in special cases 206773 closed 0     3 2016-04-08T11:55:44Z 2016-04-09T16:55:10Z 2016-04-09T16:54:10Z NONE      

Hi there,

I have a datetime issue with a certain type of (CF-compliant!) netCDF files orginating from the ESA CCI Sea Surface Temperature project. With other climate data, everthings seems fine.

When I open such a netCDF file, the datetime value(s) of the time dimension seem to be wrong. If I do

ds = xr.open_dataset(nc_path) ds.analysed_sst

I get

<xarray.DataArray 'analysed_sst' (time: 1, lat: 3600, lon: 7200)> [25920000 values with dtype=float64] Coordinates: * time (time) datetime64[ns] 1947-05-12T09:58:14 * lat (lat) float32 -89.975 -89.925 -89.875 -89.825 -89.775 -89.725 ... * lon (lon) float32 -179.975 -179.925 -179.875 -179.825 -179.775 ... Attributes: units: kelvin ...

The time dimension is

int time(time=1); :units = "seconds since 1981-01-01 00:00:00"; :standard_name = "time"; :axis = "T"; :calendar = "gregorian"; :bounds = "time_bnds"; :comment = ""; :long_name = "reference time of sst file"; :_ChunkSizes = 1; // int

and the time value is 915192000. Therefore the correctly interpreted time value must be 2010-01-01T12:00:00 which is 1981-01-01 00:00:00 plus 915192000 seconds.

Here is the link to the data: ftp://anon-ftp.ceda.ac.uk/neodc/esacci/sst/data/lt/Analysis/L4/v01.1/2010/01/01/20100101120000-ESACCI-L4_GHRSST-SSTdepth-OSTIA-GLOB_LT-v02.0-fv01.1.nc

I'm not sure whether this is actually a CF-specific issue with which xarray doesn't want to deal with. If so, could you please give some advice to get arround this. I'm sure other xarray lovers will face this issue sooner or later.

Thanks! -- Norman

 
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