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The first DECK simulation is the piControl simulation which requires a minimum of 500 years. Other experiments will all be initialized by branching of from piControl at various stages. A possible scenario is provided in the figure below. Historical_H1, 1pctCO2, and abrupt-4xCO2 would start from year 101 of piControl, amip from year 1870 of historical_H1, historical_H2 from year 151 of piControl and all remaining historical members would be spaced 50 years apart (201, 251, 301).

piControl

Initialization

Due to time constraints, piControl year 1 (0001-01-01) initial conditions are taken from a pre-existing simulation rather than starting a new spin-up from scratch. The initial conditions are 0331-01-01 of 20171228.beta3rc13_1850.ne30_oECv3_ICG.edison.

Final tuning

At the time piControl needed to start, we were still in the process of fine tuning the control simulation to reduce its long term drift in surface air temperature as much as possible. 20171228.beta3rc13_1850.ne30_oECv3_ICG.edison was the configuration with the smallest drift at the time. However, due to its limited duration (80 years), we couldn't conclusively determine whether the drift was as small as it could be. As a result, we decided to start two piControl simulations with the goal of running both of them for 50-100 years and then selecting one:

• 20180129.DECKv1a_piControl.ne30_oEC.edison : identical tuning as in beta3rc13, but with a slightly updated version of the code base.
• 20180129.DECKv1b_piControl.ne30_oEC.edison : same, except for a minor retuning of clubb_c14: 1.08 → 1.06. This is expected to only change net TOA fluxes by a few hundreds of a W/m2, but may help further reduce long-term drift (without hopefully changing its sign).