Emissions in WACCM

[duderstadtk@gmail_com]

We are running F_SD_WACCM for 2000-2002 and are interested in using the emissions (POET-REAS-GFED2) referenced by: Lamarque, J. F., et al. (2012). CAM-chem: description and evaluation ofinteractive atmospheric chemistry in the Community Earth System Model, Geosci. Model Dev., 5,  369-411, doi: 10.5194.The default emissions in building the F_SD_WACCM case are ".../2000-2100_RCP45/IPCC_emissions_RCP45*.nc"  for aircraft_NO2, CH2O, CO, NOx, and SO2.  Are these default emissions the same as the POET-REAS_GFED2 inventory...only projected into the future with RCP scenarios?  Or should we specify a new emissions path in our user_nl_cam file?  [i.e.,  ".../poet_reas_gfed2_ex/emissions*.nc"]    [e.g., on Yellowstone.../glade/p/cesm/cseg/inputdata/atm/cam/chem/emis/poet_reas_gfed2_ex]Is there anywhere in the CESM documentation that details the differences in emissions files?    Thanks!    

 

[tilmes]

The RCP4.5 emissions are descirbed for example in the following paper and are very different from the emissions that are described in Lamarque et al. (2012):
Lamarque, J.-F., G. P. Kyle, M. Meinshausen. K. Riahi, S. J. Smith, D. P. van Vuuren, A. Conley, F. Vitt. Global and regional evolution of short-lived radiatively-active gases and aerosols in the Representative Concentration Pathways. Climatic Change, doi:10.1007/s10584-011-0155-0, 2011.
You can find a summary of available emission datasets and information about their location on the Yellowstone glade disk on the Chemistry-Climate working group website http://www.cesm.ucar.edu/working_groups/Chemistry/ under:
User Support

• Introduction on how to run CESM with Chemistry:
• On Yellowstone CESM1.1 (new): Roadmap

The emission datasets are described towards the end of the 'roadmap' document.
I would agree that it makes sense to revise the F_SD_WACCM compset to point to those emissions rather than to the RCP4.5 emissions.

 

[mmills]

The specified dynamics compsets were set up to allow users to run across many time periods, increasing as more meteorological analyses became available. This is why we use the RCP4.5 emissions files, which span dates from 1850 to 2100. These are based on observations only for dates before 2006, but the interannual variability will not be important for most users.

You may chose to customize your run to use the newer emissions files you have listed. These only cover the dates from January 1, 1997 to January 1, 2011, so would the model would break at dates before or after that time period. If a newer emissions dataset becomes available that combines recent observations with future projections, such as for the upcoming CCMI project, we may revise the SD compsets to use these in future releases.

 

[duderstadtk@gmail_com]

Thanks! The explanation, links, and paper are very helpful.
The link to the latest emissions on yellowstone: /glade/p/cesm/cseg/inputdata/atm/cam/chem/emis/1992-2010 provides the surface emissions that our simulations need.
I do have a question about the external forcing namelist variable "ext_frc_specifier" -- which currently has a default setting in F_SD_WACCM of:
ext_frc_specifier = 'NO2 -> /glade/p/cesm/cseg/inputdata/atm/cam/chem/2000-2100_RCP45/IPCC_emissions_RCP45_aircraft_NO2_2000-2100_1.9x2.5.nc'
(I am assuming these are aircraft NO2 emissions.) Is there a more recent file we should be using?

Thanks again for the thorough response.