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Difference between revisions of "NetCDF time coordinate"

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imported>Lang Guenther
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imported>Lang Guenther
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[[de:NetCDF Zeitkoordinate]]
 
[[de:NetCDF Zeitkoordinate]]
For further information please follow link "in other languages" (Deutsch).
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=Introduction=
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Date, time and calendar plus (optional) use of time intervals.
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=Time information in a netCDF file=
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==Dimensions==
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dimensions:   
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: time = ''number of time steps'' or ''UNLIMITED''; 
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: bnd  = 2 ;
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Comment: In case the number of time steps is known before-hand, '''Bert Jagers''' (Deltares) recommends to use a fixed length instead of an UNLIMITED dimension due to performace reasons. But this only works for variables not exceeding 4 GiB.
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==Variables== 
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===Coordinate ''time''===
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double time(time) ;   
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: time:standard_name = "'''time'''" ;   
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: time:long_name = "time" ;   
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: time:units = "''time units'' since YYYY-MM-DD hh:mm:ss ''zone''" ;
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: time:axis = "T"
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: time:calendar = "gregorian"
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: time:bounds = "timebnd"
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Comment:
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* For ''time units'' the following units are common:
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*# ''seconds'',
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*# ''minutes'',
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*# ''hours'', and
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*# ''days''.
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* Specification of ''zone'' is optional (default is UTC). Some examples for other time zones:
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*# ''zone'' = +1:00 for CET (Central European Time), or
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*# ''zone'' = +2:00 for CEST (Central European Summer Time).
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* Attribute ''bounds'' must be specified, in case (some) data are e.g. mean or integral (sum) values with respect to time. Examples: Daily mean temperature, daily rainfall. These data must possess attribute ''cell_methods'' with e.g. "time: mean" or "time: sum". See also [http://cfconventions.org/cf-conventions/v1.6.0/cf-conventions.html#cell-methods CF Conventions "cell_methods"].
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===Time intervals===
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double timebnd(time,bnd) ;   
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Comment:
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* timebnd(n,1) is equivalent to the ''lower'' bound for the n-th time step.
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* timebnd(n,2) is equivalent to the ''upper'' bound for the n-th time step.
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* Subsequent intervals may not be continous.
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* For continuous intervals timebnd(n,2) == timebnd(n+1,1) holds.
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=Remarks=
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* A double precision variable should be used for ''time'' to guarantee sufficient accuracy..
 
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back to [[NetCDF]]
 
back to [[NetCDF]]
 
----
 
----
 
[[Overview]]
 
[[Overview]]

Latest revision as of 13:56, 18 April 2016


Introduction

Date, time and calendar plus (optional) use of time intervals.

Time information in a netCDF file

Dimensions

dimensions:

time = number of time steps or UNLIMITED;
bnd = 2 ;

Comment: In case the number of time steps is known before-hand, Bert Jagers (Deltares) recommends to use a fixed length instead of an UNLIMITED dimension due to performace reasons. But this only works for variables not exceeding 4 GiB.

Variables

Coordinate time

double time(time) ;

time:standard_name = "time" ;
time:long_name = "time" ;
time:units = "time units since YYYY-MM-DD hh:mm:ss zone" ;
time:axis = "T"
time:calendar = "gregorian"
time:bounds = "timebnd"

Comment:

  • For time units the following units are common:
    1. seconds,
    2. minutes,
    3. hours, and
    4. days.
  • Specification of zone is optional (default is UTC). Some examples for other time zones:
    1. zone = +1:00 for CET (Central European Time), or
    2. zone = +2:00 for CEST (Central European Summer Time).
  • Attribute bounds must be specified, in case (some) data are e.g. mean or integral (sum) values with respect to time. Examples: Daily mean temperature, daily rainfall. These data must possess attribute cell_methods with e.g. "time: mean" or "time: sum". See also CF Conventions "cell_methods".

Time intervals

double timebnd(time,bnd) ;

Comment:

  • timebnd(n,1) is equivalent to the lower bound for the n-th time step.
  • timebnd(n,2) is equivalent to the upper bound for the n-th time step.
  • Subsequent intervals may not be continous.
  • For continuous intervals timebnd(n,2) == timebnd(n+1,1) holds.

Remarks

  • A double precision variable should be used for time to guarantee sufficient accuracy..

back to NetCDF


Overview