Open matthewhoffman opened 6 years ago
xylar
commented
6 years ago I fully support (and would happily contribute to) any effort to address this issue. The non-CF-compliant time issue has been a big headache in MPAS-Analysis, up there with not having a _FillValue attribute (#1380).
matthewhoffman
commented
6 years ago Discussion on 2/26/18: Consider making this a framework streams capability that automatically adds the CF-compliant time variable to output streams. However, it also appears possible to leave this up to each core, using existing Registry capabilities. Having a standard implementation in framework would seem more convenient, but it may preclude core-specific choices about the origin time and bounds.
The way MPAS handles time, is not CF compliant. The xtime string cannot easily be parsed by many tools.
A CF-compliant solution was summarized by @czender:
The solution is to use CF-compliant time coordinate much like CAM does. It's a numeric (not string) -valued coordinate with a UDUnits "time_elements since base_time" units attribute, and an optional "calendar" attribute, and an optional "bounds" variable (both highly recommended), e.g.,
zender@aerosol:~/data/ne30/raw$ ncks -v time ${DATA}/ne30/raw/famipc5_ne30_v0.3_00007.cam.h1.2001-01-01-00000.nc netcdf famipc5_ne30_v0.3_00007.cam.h1.2001-01-01-00000 { dimensions: nbnd = 2 ; time = UNLIMITED ; // (30 currently)
variables: double time(time) ; time:long_name = "time" ; time:units = "days since 2001-01-01 00:00:00" ; time:calendar = "noleap" ; time:bounds = "time_bnds" ;
double time_bnds(time,nbnd) ; time_bnds:long_name = "time interval endpoints" ;
data: time = 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 ;
time_bnds = 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 28, 28, 29 ;
} // group /
These can easily be converted to legible dates by, e.g.,
zender@aerosol:~/data/ne30/raw$ ncks --cal -v time ${DATA}/ne30/raw/famipc5_ne30_v0.3_00007.cam.h1.2001-01-01-00000.nc netcdf famipc5_ne30_v0.3_00007.cam.h1.2001-01-01-00000 { dimensions: nbnd = 2 ; time = UNLIMITED ; // (30 currently)
variables: double time(time) ; time:long_name = "time" ; time:units = "days since 2001-01-01 00:00:00" ; time:calendar = "noleap" ; time:bounds = "time_bnds" ;
double time_bnds(time,nbnd) ; time_bnds:long_name = "time interval endpoints" ;
data: time = "2001-01-01", "2001-01-02", "2001-01-03", "2001-01-04", "2001-01-05", "2001-01-06", "2001-01-07", "2001-01-08", "2001-01-09", "2001-01-10", "2001-01-11", "2001-01-12", "2001-01-13", "2001-01-14", "2001-01-15", "2001-01-16", "2001-01-17", "2001-01-18", "2001-01-19", "2001-01-20", "2001-01-21", "2001-01-22", "2001-01-23", "2001-01-24", "2001-01-25", "2001-01-26", "2001-01-27", "2001-01-28", "2001-01-29", "2001-01-30" ;
time_bnds = "2001-01-01", "2001-01-01", "2001-01-01", "2001-01-02", "2001-01-02", "2001-01-03", "2001-01-03", "2001-01-04", "2001-01-04", "2001-01-05", "2001-01-05", "2001-01-06", "2001-01-06", "2001-01-07", "2001-01-07", "2001-01-08", "2001-01-08", "2001-01-09", "2001-01-09", "2001-01-10", "2001-01-10", "2001-01-11", "2001-01-11", "2001-01-12", "2001-01-12", "2001-01-13", "2001-01-13", "2001-01-14", "2001-01-14", "2001-01-15", "2001-01-15", "2001-01-16", "2001-01-16", "2001-01-17", "2001-01-17", "2001-01-18", "2001-01-18", "2001-01-19", "2001-01-19", "2001-01-20", "2001-01-20", "2001-01-21", "2001-01-21", "2001-01-22", "2001-01-22", "2001-01-23", "2001-01-23", "2001-01-24", "2001-01-24", "2001-01-25", "2001-01-25", "2001-01-26", "2001-01-26", "2001-01-27", "2001-01-27", "2001-01-28", "2001-01-28", "2001-01-29", "2001-01-29", "2001-01-30" ;
} // group /