中国科学院 | 大气所 | LASG主页 | 加入收藏
 
中文版 | English
 
 
 
CMIP5 news

Dear all,

Here are some items that should be of interest to those of you participating in CMIP5.  Please pass on this information, especially to those who are responsible for preparing the model output for the CMIP5 archive.

1. 
For those of you doing the emissions-driven simulations:  Unless it's too late, it is recommended that the recently produced gridded fossil fuel emissions data from Andres (hosted by IPSL)  and the the land use data from Houghton (hosted at MPI) should be used for the historical simulations.  More information should appear soon on the CMIP5 website. 

These fossil fuel emissions data can be retrieved from:
http://dods.ipsl.jussieu.fr/cpipsl/ANDRES/
File name is : CMIP5_gridcar_CO2_emissions_fossil_fuel_Andres_1751-2007_monthly_SC_mask11.nc
It is a monthly dataset, units are gC/m2/s
Also provided is an ascii file that contains the globally integrated emissions for every month.
CMIP5_gridcar_CO2_emissions_fossil_fuel_Andres_1751-2007_monthly_SC_grid1x1.txt

The land use file can be found at MPI:
http://www.mpimet.mpg.de/en/wissenschaft/land-im-erdsystem/wechselwirkung-klima-biogeosphaere/landcover-change-emission-data.html
File name is:  carbon_emissions_landuse_20person.nc
It is an annual dataset, units are also gC/m2/s

2. 
Again for those of you with coupled carbon climate models (ESM's):  The CMIP5 expts. 5.4 and 5.5 are designed to isolate the climate change effects on carbon uptake from the uptake due to CO2 concentration increases (in the absence of climate change). Originally there were two options proposed for these experiments: analyze 1%/yr CO2 increase runs or analyze historical+RCP4.5 runs. At the WGCM meeting last month and in subsequent discussion, it was decided that for groups who have not yet performed these experiments, it would be better if they would base these runs on the idealized 1%/yr CO2 increase (rather than the historical+RCP4.5 simulations). There will, of course, also be interest in the historical+RCP4.5 runs, so groups who have already done these runs, should contribute them to the archive.

3.  We recently posted a revised document describing the model output requirements for CMIP5 (see http://cmip-pcmdi.llnl.gov/cmip5/output_req.html?submenuheader=2#metadata ).  (Those of you who have chosen *not* to use CMOR2 to rewrite your model output should study this document carefully; those of you using CMOR may refer to the CMOR documentation for most of the information you need to know. The CMOR documentation has also been recently revised with expanded descriptions of what you must supply.)  At the beginning of the output requirements document there is a link directing the user to the bottom of the document where a list of the changes that were made can be found.  Nearly all the changes were simply to improve clarity.  Please note, however, that a new global attribute is now required for most simulations (parent_experiment_rip), which identifies which ensemble member the child experiments was spawned from.  This information will be essential for many CMIP5 studies.

4.  The so-called "data reference syntax" document has also been revised.  Again, many of the changes should simply make it easier to understand.  Data providers will be especially interested in the official "short names" of the CMIP5 experiments, since these names are used in constructing filenames. This document can be obtained through the following link:  http://cmip-pcmdi.llnl.gov/cmip5/output_req.html?submenuheader=2#req_format

5.  The latest version of CMOR2 was just released on 12 November 2010.  The changes made were summarized on an announcement made to those of you on the cmor email list.  It also includes the latest "requested variables" CMOR tables (also posted at http://cmip-pcmdi.llnl.gov/cmip5/output_req.html?submenuheader=2#req_list ), which includes a number of  formerly missing "standard names", and also some corrections. Please download the latest version of CMOR, the CMOR tables and the documentation before continuing to process your data.

6.  At the WGCM meeting there was agreement that it would be useful for model evaluation and detection/attribution studies to extend the CMIP5 historical runs to near-present (as we have for AMIP), rather than ending them in 2005.  In fact since the CMIP5 project is ongoing, it would be useful to have simulations extended to at least the end of 2012 using some estimate of recent and future forcing.  There is, however, no community-wide accepted observationally-based concentration/emissions past 2005.  Groups are therefore free to use whatever concentrations, solar forcing, SO2 emissions etc. they want to use in extending these runs.  It is also o.k. for detection/attribution studies to simply splice one of the RCP runs to the end of the historical simulations.  No matter what forcing is chosen it is important to consider the following:

a) The groups should take care that there are no substantial discontinuities in the forcing in passing from the "past" to the "future", defined to be the end of 2005. 

b) It is recommended that if an ensemble of "all-forcings" historical simulations have been run, then *each* member of the ensemble should be carried to the end of 2012.  Thus, a full ensemble of  runs (through year 2012) would be available for analysis.

c)  It is recommended that all historical runs with only a subset of forcing (e.g., GHG only, natural forcing only) should also be extended through the year 2012.

d) If one of the RCP forcings is used to extend the historical run, it may not matter too much which RCP is chosen, and CMIP5 makes no strong recommendation. If a modeling group has no preference, they might choose the RCP8.5 expt., as at least one group (the Hadley Centre) has made this choice already.

e) For all-forcing (anthro + natural) historical runs, the extended portions of these runs should be treated as a new runs spawned from the parent historical runs at the end of year 2005.  If this run is forced by an RCP that extends at least to the end of the 21st century, then nothing special needs to be done.  If, however, some other forcing is used or if the run is an RCP run that is truncated after a few years (say ending in 2012), then the run should be considered a "historical extension" experiment with its output placed in a directory named historicalExt.  The "forcing" attribute (a netCDF global attribute) should describe what forcing is used to extend the run, and this information will also need to be recorded when entering information about the run in the METAFOR questionnaire.   Placing the extended portion of the historical runs in a separate place will help guard against users assuming that these runs are necessarily based on historically-measured concentrations, land-use changes, solar forcing, etc.  For these historicalExt experiments, the ensemble member (designated by the "rip" value appearing in the filename and recorded as netCDF global attributes) will be identical to the historical run it extends. Also for the runs, the identifying netCDF global attributes should be defined as follows: experiment="historical extension" and experiment_id="historicalExt". The "Data Reference Syntax" document and the CMOR tables will be revised shortly to include these "new" experiments. 

f) If one chooses to do historical runs with only a subset of forcing (e.g., GHG only, natural forcing only, single-forcing experiments, etc.), then all the data for the complete historical period and in the extended portion (from 2006-2012) would be kept together, no matter what forcing was used (in the historicalNat, historicalGHG, or historicalMisc directories).  (In these clearly "unrealistic" cases, naive users will be less likely to access the output and possibly misuse it.)

7.  For your information, We've posted (see http://cmip-pcmdi.llnl.gov/cmip5/terms.html?submenuheader=3 ) the latest (and final) version of the the two different terms of use governing the CMIP5 model output.  It looks like about half the groups plan to release their data for "unrestricted" use and half for "non-commercial educational and research purposes" only. 

Carry on!

Best regards,
your faithful CMIP5 comrades (Karl's lame attempt to try to develop a little esprit de corps here),
Karl and Ron

 
通信地址:北京9804信箱LASG  邮政编码:100029   E-mail:lasg@lasg.iap.ac.cn  
京ICP备06004370号