Community Earth System Model (CESM) for CMIP6 Office of Science

Target CESM2 and CMIP6 versions: ocean at 1o AOGCM physical climate (1o, low-top) + biogeochemistry (1o, CO2 emission and/or concentration driven, low-top) + atmospheric chemistry + biogeochemistry (1o, CO2 emission driven, high-top; WACCM) AOGCM physical climate (1/4o atm, low-top) (a few simulations with AOGCM 1/4o atm, 1/10o ocean) Low-top: 32 levels up to 40 km High-top: 70 levels up to 150 km

2015-2016 Timeline for CESM2 development now Spring 2015 June 2015 Oct 1 2015 Spring 2016 June 2016 Decision on CAM5.5 CAM5.5 to developers Coupled simulations Coupled simulations CESM2 FV-1o Interim versions of CLM5 POP2 CICE5 BGC Chemistry WACCM Others Begin CMIP6 simulations ~fall, 2016 All components for FV-1o frozen by Oct. 15 2015 FY 2016 CAM6 development (SE dycore) Coupled simulations CESM2 SE-1/4o All WG meetings Feb 8-11 2016 Code delivery Potential code delivery Potential code development Assembling and optimizing coupled model

CESM participation to MIPs Diagnostic MIPs *Interested in participating but worried about data requirements **Participation to HighResMIP limited to AMIP simulation

CMIP6 DECK + Tier 1 Requirements 1o versions CAM5: ≈12,800 years CAM5-BGC: ≈10,500 WACCM-BGC: ≈ 7,300 Total cost: ≈150M core-hours 1/4o version CAM5: ≈ 2,200 years Total cost: ≈350M core-hours 1) This is only for DECK+Tier 1 while a lot of interesting science resides in Tier 2/3 experiments 2) A large factor is #years performed at high-resolution. Mention overlap period and Rich’s talk Yellowstone core-hours; 1 year ≈ 700M core-hours

Improved throughput of WACCM on Yellowstone Figure courtesy of S. Santos and F. Vitt, with help from J. Dennis and many others FV 1-degree 135 advected tracers: Target 8-10 simulated years per day

NCAR CMIP6 Planning CMIP6 Simulation CMIP6 Simulations NWSC-2 CMIP6 Analysis and Papers (will take advantage of CMIP analysis platform) CMIP6 Data to ESGF Ramp-up Late-2016--2017 Production 2018 Production CMIP6 Post-Processing Ramp-down CMIP6 Simulation CMIP6 Simulations CESM-2 Validation NWSC-2 Yellowstone The thing to mention here is the nnew CMIP analysis platform for which we got funding and which will start soon, first with cmip5 data. We will also be able to take advantage of the overlap in computing power January 2016 January 2017 January 2018 January 2019 January 2020 CESM2 Release DOE (NERSC, Argonne); Univ. Illinois (Blue Waters)

Staging simulations for PI control Ocean spin-up from Levitus (will need a few iterations) Atmospheric chemistry simulations (with WACCM) must be performed first to generate fields necessary for all other configurations Levitus Land initialization CAM w/ old forcings CAM Stabilized climate Stabil. Land initialization Ocean BGC initialization WACCM This will make an unprecedented use of WACCM (with full tropospheric and stratospheric chemistry, including tropospheric and volcanic aerosols) to generate all chemical fields needed by the other versions of CESM. This has required tremendous optimization of WACCM to get a throughput of approx. 10 years per day (a joint effort by CISL/CGD/ACOM software engineer) (next slide) Stabil. Land initialization Ocean BGC initialization CAM

Exploring representing volcanic emission and evolution in CESM for CMIP Volcanic emissions of sulfur are explicitly represented in CAM/WACCM through a source of sulfur dioxide (SO2). Then the model computes the chemical and microphysical evolution of the plume (here Pinatubo and later). The cimparison shows the amazing quality of the simulation of the aerosol optical depth (WACCM, black line) and the observations (green and gre, see bottom panel for 1992). This shows both the short term and long-term evolution of the volcanic plume. This has considerably improved the simulation of the climate impact of Pinatubo. It also enable to do simulations of any volcano in the past 55ºN Mills et al., 2015