CESM2 Large Ensemble Community Project
We are pleased to announce the launch of the CESM2 Large Ensemble in partnership with the IBS Center for Climate Physics in South Korea. When completed, the CESM2 Large Ensemble will consist of 100 members at 1 degree spatial resolution covering the period 1850-2100 under CMIP6 historical and SSP370 future radiative forcing scenarios. The entire ensemble is expected to be completed by the end of February 2021, and the data sets should become available via the Climate Data Gateway by the beginning of May 2021. A reference paper describing the ensemble will be posted by mid-March 2021.
Unlike the CESM1 Large Ensemble, the CESM2 Large Ensemble will use a combination of different oceanic and atmospheric initial states to create ensemble spread as follows.
- Members 1-10: These will begin from years 1001, 1021, 1041, 1061, 1081, 1101, 1121, 1141, 1161, and 1181 of the 1400-year pre-industrial control simulation. This segment of the control simulation was chosen to minimize drift.
- Members 11-90: These begin from 4 pre-selected years of the pre-industrial control simulation based on the phase of the Atlantic Meridional Overturning Circulation (AMOC). For each of the 4 initial states, there will be 20 ensemble members created by randomly perturbing the atmospheric temperature field by order 10^-14K. The chosen start dates (model years 1231, 1251, 1281, and 1301) sample AMOC and Sea Surface Height (SSH) in the Labrador Sea at their maximum, minimum and transition states.
- Members 91-100: These will begin from years 1011, 1031, 1051, 1071, 1091, 1111, 1131, 1151, 1171, and 1191 of the 1400-year pre-industrial control simulation. This set will include the extensive "MOAR" output, which can be used to drive regional climate models.
The initialization design will allow assessment of oceanic (AMOC) and atmospheric contributions to ensemble spread, and the impact of AMOC initial-condition memory on the global earth system.