I have 365 daily netCDF files for the year 1980. These files are located in a folder that has data from multiple years (1979-2013).
When I open the 1980 files using,
files = glob.glob("/mnt/nfs/home/solomon/Data/CFSR/NetCDFs_1979-2013/Subset/data_1980*")
ds = xarray.open_mfdataset(files, engine="netcdf4")
The time stamp seems to be incorrect. When I print out the time, I get the following:
ds.time.sortby("time")
Out[28]:
<xarray.DataArray 'time' (time: 3286)>
array(['1979-01-07T00:00:00.000000000', '1979-01-07T03:00:00.000000000',
'1979-01-07T06:00:00.000000000', ..., '2013-12-23T18:00:00.000000000',
'2013-12-23T21:00:00.000000000', '2013-12-24T00:00:00.000000000'], dtype='datetime64[ns]')
Coordinates:
* time (time) datetime64[ns] 1979-01-07 1979-01-07T03:00:00 ...
Attributes:
standard_name: time
axis: T
To check if the other files in the folder are being read, I changed the contents of the folder (i.e. I removed the 2012 files), but I still get the same time series as before. I am not sure what is wrong!
Out[29]:
<xarray.DataArray 'time' (time: 3286)>
array(['1979-01-07T00:00:00.000000000', '1979-01-07T03:00:00.000000000',
'1979-01-07T06:00:00.000000000', ..., '2013-12-23T18:00:00.000000000',
'2013-12-23T21:00:00.000000000', '2013-12-24T00:00:00.000000000'], dtype='datetime64[ns]')
Coordinates:
* time (time) datetime64[ns] 1979-01-07 1979-01-07T03:00:00 ...
Attributes:
standard_name: time
axis: T
The NetCDF data has the metadata as follows (using ncdump -h):
svimal@lettenmaierlab06:/mnt/nfs/home/solomon/Data/CFSR/NetCDFs_1979-2013/Subset$ ncdump -h data_19800530.nc
netcdf data_19800530 {
dimensions:
lon = 503 ;
lat = 170 ;
time = UNLIMITED ; // (1 currently)
variables:
double lon(lon) ;
lon:standard_name = "longitude" ;
lon:long_name = "longitude" ;
lon:units = "degrees_east" ;
lon:axis = "X" ;
double lat(lat) ;
lat:standard_name = "latitude" ;
lat:long_name = "latitude" ;
lat:units = "degrees_north" ;
lat:axis = "Y" ;
double time(time) ;
time:standard_name = "time" ;
time:units = "hours since 1999-5-16 00:00:00" ;
time:calendar = "standard" ;
time:axis = "T" ;
float air_temp(time, lat, lon) ;
air_temp:long_name = "air temperuature (C)" ;
air_temp:_FillValue = -9.99e+08f ;
air_temp:missing_value = -9.99e+08f ;
float vp(time, lat, lon) ;
vp:long_name = "vapor pressure (kPa)" ;
vp:_FillValue = -9.99e+08f ;
vp:missing_value = -9.99e+08f ;
float pressure(time, lat, lon) ;
pressure:long_name = "pressure (kPa)" ;
pressure:_FillValue = -9.99e+08f ;
pressure:missing_value = -9.99e+08f ;
float windspd(time, lat, lon) ;
windspd:long_name = "wind (m/s)" ;
windspd:_FillValue = -9.99e+08f ;
windspd:missing_value = -9.99e+08f ;
float shortwave(time, lat, lon) ;
shortwave:long_name = "downward shortwave (W/m^2)" ;
shortwave:_FillValue = -9.99e+08f ;
shortwave:missing_value = -9.99e+08f ;
float longwave(time, lat, lon) ;
longwave:long_name = "downward longwave (W/m^2)" ;
longwave:_FillValue = -9.99e+08f ;
longwave:missing_value = -9.99e+08f ;
float precip(time, lat, lon) ;
precip:long_name = "precipitation (mm/hr)" ;
precip:_FillValue = -9.99e+08f ;
precip:missing_value = -9.99e+08f ;
// global attributes:
:CDI = "Climate Data Interface version ?? (http://mpimet.mpg.de/cdi)" ;
:Conventions = "CF-1.4" ;
:history = "Tue Mar 20 14:36:48 2018: ncea -d lat,41.375,83.625 -d lon,181.375,306.875 /mnt/nfs/home/solomon/Data/CFSR/NetCDFs_1979-2013/data_19800530.nc /mnt/nfs/home/solomon/Data/CFSR/NetCDFs_1979-2013/Subset/data_19800530.nc\n",
"Tue Mar 20 14:36:44 2018: cdo -f nc import_binary /mnt/nfs/home/solomon/Data/CFSR/CFSR-LAND_Global_0.25deg_data_changed.ctl /mnt/nfs/home/solomon/Data/CFSR/NetCDFs_1979-2013/data_19800530.nc" ;
:CDO = "Climate Data Operators version 1.7.0 (http://mpimet.mpg.de/cdo)" ;
:NCO = "\"4.5.4\"" ;
:nco_openmp_thread_number = 1 ;
}
The time attribute says
time = UNLIMITED ; // (1 currently)
I am not sure what this means, could this be the issue?
Are you sure that your use of glob.glob() is only returning netCDF files with times in 1980?
I would suggest a spot-check with an explicit loop (skipping open_mfdataset):
files = glob.glob("/mnt/nfs/home/solomon/Data/CFSR/NetCDFs_1979-2013/Subset/data_1980*")
for path in files:
ds = xarray.open_dataset(path, engine="netcdf4")
print(path, ds.time.values)
Side note: it's best to pass the glob string directly into open_mfdataset() rather than explicitly calling glob.glob(). It is a little more succinct, and xarray also calls sorted() on glob strings that it parses, rather than relying on the platform specific order of the list returned by glob.glob().