Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

Answers to Frequently Asked Questions

SSTs: The idea is to probe the configurations used in the CMIP5 transients, so we request that groups either save the ACCMIP diagnostics directly during their CMIP5 simulations if possible, or if rerunning with fixed SSTs to run the ACCMIP simulations once the transient climate runs pass a particular time period and the SSTs become available.

Ozone climatology: Some chemistry/aerosol models will run with interactive stratospheric chemistry while others will prescribe ozone in the stratosphere and only run with detailed tropospheric chemistry. The first group of models is encouraged to provide the stratospheric diagnostics that are defined in the output tables, while the latter group of models is encouraged to specify ozone according to the AC&C/SPARC ozone database that will be made available on at PCMDI mid July 2009.A 4D ozone climatology has been prepared for models that do not simulate their own ozone (either everywhere or in the stratosphere). A dataset merging model results with stratospheric observations is available at: http://cmip-pcmdi.llnl.gov/cmip5/

Methane: Our recommendation is to use observed concentrations for the past, and then if you have a model of the methane cycle to switch to simulations based on emissions for the future. This of course requires a bit of effort to get a match at the changeover point, but gives the most realistic scenario in the past.

Natural emissions: Other than biomass burning, these are not specified in the emission inventories. Hence each group will use their own (in many models these cannot be easily separated out anyway). There is no attempt to match these across models. The ACCMIP_2 set of runs is designed to examine the impact of these differences via several short simulations.

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