CESM2 Large Ensemble

The CESM2 Large Ensemble consists of 100 members at 1 degree spatial resolution covering the period 1850-2100 under CMIP6 historical and SSP370 future radiative forcing scenarios. Two separate sets of biomass burning emissions forcing files were used within the ensemble. Members 1-50 were forced with CMIP6 protocols identical to those used in Danabasoglu et al. (2020) in the paper for CESM2. For members 51-100, the most relevant species for biomass burning fluxes from the CMIP6 protocols were smoothed with an 11-year running mean filter, impacting the fluxes over the years 1990-2020.The CESM2 Large Ensemble uses a combination of different oceanic and atmospheric initial states to create ensemble spread as follows: Members 1-10: These 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 are 20 ensemble members created by randomly perturbing the atmospheric temperature field on the order of -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 begin from years 1011, 1031, 1051, 1071, 1091, 1111, 1131, 1151, 1171, and 1191 of the 1400-year pre-industrial control simulation. This set includes the extensive "MOAR" output, which can be used to drive regional climate models.The initialization design allows assessment of oceanic (AMOC) and atmospheric contributions to ensemble spread, and the impact of AMOC initial-condition memory on the global earth system.

CESM2大集合（CESM2 Large Ensemble）数据集包含100个集合成员，空间分辨率为1度，时间覆盖1850年至2100年，采用耦合模式比较计划第六阶段（Coupled Model Intercomparison Project Phase 6, CMIP6）的历史情景与SSP370未来辐射强迫情景。本集合使用了两套独立的生物质燃烧排放强迫文件。其中成员1至50的强迫方案与Danabasoglu等人2020年发表论文中针对CESM2所采用的CMIP6协议完全一致。对于成员51至100，CMIP6协议中与生物质燃烧通量最相关的物种采用11年滑动平均滤波器进行平滑处理，该操作对1990年至2020年期间的通量产生影响。

CESM2大集合通过组合不同的海洋与大气初始状态以生成集合离散度，具体设计如下：
成员1至10：初始时刻取自1400年预工业控制模拟的1001、1021、1041、1061、1081、1101、1121、1141、1161及1181年。选取该段控制模拟是为了最小化模拟漂移。
成员11至90：基于大西洋经向翻转环流（Atlantic Meridional Overturning Circulation, AMOC）的相位，从预工业控制模拟中选取4个预定义年份作为初始时刻。针对这4个初始状态，各通过对大气温度场施加约-14K量级的随机扰动，生成20个集合成员。所选起始年份（模型年份1231、1251、1281及1301）分别采样了拉布拉多海区域AMOC与海表高度（Sea Surface Height, SSH）的极大值、极小值及过渡状态。
成员91至100：初始时刻取自1400年预工业控制模拟的1011、1031、1051、1071、1091、1111、1131、1151、1171及1191年。该集合子集包含了丰富的"MOAR"输出结果，可用于驱动区域气候模式。

该初始化设计可用于评估海洋（AMOC）与大气因素对集合离散度的贡献，以及AMOC初始条件记忆性对全球地球系统的影响。