IPCC output requirements adaptation to PMIP 2

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IPCC output requirements adaptation to PMIP 2

You will find on this page how the IPCC output requirements have been adapted to the PMIP 2 project.

The differences are listed for each IPCC output document (as defined in the PMIP 2 and the IPCC Requirements page), in approximatively the order in which they appear in the document.

Requirements for IPCC Standard Output

Data format, data structure, and file composition requirements
- The files submitted for the PMIP 2 experiments have to be supplied on regular grids, unless they are supposed to be used in the lagrangian analysis subproject.
- Oceanic fields can be supplied on model levels (i.e. depths different from the standard Levitus levels.
- Unlike IPCC, PMIP 2 won't have ensemble simulations, and it is therefore enough to store the variables in a model/experiment/frequency hierarchy.
- Eventhough the metadata stored in each file makes the file unique, we also want to have unique file names. Please use the following file name template:
  
      varname_table_experiment_modelorlab[_time_range].nc
  
  experiment being one of: pmip2_0k_oa, pmip2_0k_oav, pmip2_6k_oa, pmip2_6k_oav, pmip2_21k_oa, pmip2_21k_oav
  
  If a data file has to be split into several sub-files along the time axis, use either
      _yyyy_YYYY
  if the file covers the whole years yyyy to YYYY, or
      yyyymmdd_YYYYMMDD

Requirements for output variables

The variable names (in the NetCDF files, and in the file names), as well as the standard_names and units attributes must be the names, standard_names and units specified in the PMIP 2 Variables' section (A, O, S, I).

The value of the cell_methods attribute depends on the PMIP 2 frequency used to save the variable.

Frequency	cell_methods
DA	`time: mean` ???
SE	`time: mean` ???
MO	`time: mean` ???
AN	`time: mean` ???

The value of the Description column in the PMIP 2 Variables' section (A, O, S, I).

Requirements for coordinate variables
- It does not really mean anything to use absolute times for the paleoclimate simulations of the PMIP 2 project. The units of the time axis should therefore be the time since the beginning of the experiment (not including spin-up). More precisely, the units attribute should be set to
      "days since 0001-1-1"
  and the numerical value of the first time step should be 0. (zero): the first saved time step of a variable is January 1st of year 1. It is the file name and the value of the experiment_id global attribute of the file that will indicate to what experiment a file is related, not the values of the time axis...
  
  The same convention applies for the control experiment!
  
  The calendar attribute of the time axis has to be set to either "360_day" or "365_day", depending on the model.
  
  Note: the CF convention makes it possible to use something like
      time:calendar = "126 kyr B.P." ;
      time:month_lengths = 34, 31, 32, 30, 29, 27, 28, 28, 28, 32, 32, 34 ;
  for a paleoclimate time axis, but for now, it seems safer to use the more standard approach listed above (this will hopefully ensure that more CF-aware software can deal with our data).

Requirements for global attributes

The value of project_id must be PMIP 2.
The value of realization must be 1 (integer value one).

The value of experiment_id must be the short name and the long experiment name one of the PMIP 2 experiments:

e.g. experiment_id = "PMIP2_0K_OA Pre-industrial Ocean-Atmosphere PMIP2 experiment"

Short name	Long experiment name
PMIP2_0K_OA	Pre-industrial Ocean-Atmosphere PMIP2 experiment
PMIP2_0K_OAV	Pre-industrial Ocean-Atmosphere-Vegetation PMIP2 experiment
PMIP2_6K_OA	Mid-Holocene 6k Ocean-Atmosphere PMIP2 experiment
PMIP2_6K_OAV	Mid-Holocene 6k Ocean-Atmosphere-Vegetation PMIP2 experiment
PMIP2_21K_OA	Last Glacial Maximum Ocean-Atmosphere PMIP2 experiment
PMIP2_21K_OAV	Last Glacial Maximum Ocean-Atmosphere-Vegetation PMIP2 experiment

The value of [experiment_id] in the title attribute must be the same as the experiment_id attribute described above.

IPCC Standard Output

CMOR IPCC configuration tables

The PMIP 2 CMOR configuration files have the following name template :
PMIP2_table_[vartype]_[subtype]
where vartype is the type of variable (Atmosphere, Ocean, land-Surface and vegetation, Ice), and subtype is a two character (more characters later, if the need arises) string specifying the output frequency.

The structure of the tables is as close as possible to what is required by IPCC, but the frequency subtypes have been chosen to be easier to remember:

Mean type	IPCC subtype	PMIP2 subtype
Time independent (fixed)	1	FX
Seasonal cycle (SE)	n/r	SE
Yearly (AN)	n/r	AN
Monthly	1	MO
Daily	2	DA
3-hourly	3	n/r
Extreme indices	4	n/r
Radiative forcing (monthly)	5	n/r
Xtra-high frequencies requested by some sub-projects (but not stored in the database)
Daily resolution (variables not requested in DA)	n/r	X1
12-hourly resolution	n/r	X2
6-hourly resolution	n/r	X4

n/r = not requested

Note: make sure you always use the latest version of the tables! The version number is the date of the most recently modified table. You can grab the latest version of each file in the table below, or (better) get the tar file with all the tables.

The current version is (year_month_day) : 05_03_14.

CMOR configuration tables

History of changes

Tables in a tar file

PMIP2_table_A_FX

PMIP2_table_A_SE

PMIP2_table_A_MO

PMIP2_table_A_DA

PMIP2_table_O_SE

PMIP2_table_O_AN

PMIP2_table_O_MO

PMIP2_table_S_SE

PMIP2_table_S_AN