ModE-Sim - A medium size AGCM ensemble to study climate variability during the modern era (1420 to 2009)

ModE-Sim (short for Modern Era Simulations) is a medium-size ensemble of model simulations using the ECHAM6 atmosphere general circulation model (model version 6.3.5p2, doi:10.17617/2.1810480). Its setup is based on the PMIP4 experiments, but uses a forced AGCM rather than a fully coupled model.

ModE-Sim was originally designed to form the a-priori state for a climate reconstruction (Modern Era Reanalysis, ModE-RA, to be found as separate experiment within this WDC project) that uses an offline data assimilation technique to combine the output of ModE-Sim with historical climate information. However, beyond its original purpose ModE-Sim on its own can be used as a tool to study climate variability, providing a high number of posible climate states that are physically plausible under the given forcings and boundary conditions. This might include, e.g. the separation of internal variability from the response to externally forced signals, understanding of teleconnection patterns, or the study of extreme events.

The ensemble uses observed/reconstructed forcings and boundary conditions, while accounting in uncertainties in these. For 1420 to 1850 we provide a 60 member ensemble grouped in three subsets using SST and sea ice reconstructions as boundary conditions. Two of these subsets use PMIP4 radiative forcings, while a third one uses a 20-member ensemble of perturbed volcanic forcings from the easy volcanic aerosol (EVA) model to account for uncertainties in the strength and the timing of volcanic eruptions. For 1850 to 2009 ModE-Sim offers 36 members grouped in two subsets, all using PMIP4 radiative forcings. As ocean boundary conditions 20 of the simulations use different realizations of HadISST2, while the remaining 16 members use linear combinations of the latter.

Reference for ModE-Sim:
Hand, Ralf; Samakinwa, Eric; Lipfert, Laura; Brönnimann, Stefan. (2023). ModE-Sim – a medium-sized atmospheric general circulation model (AGCM) ensemble to study climate variability during the modern era (1420 to 2009). doi:10.5194/gmd-16-4853-2023

ModE-Sim（简称现代时期模拟）是一个中等规模的模型模拟集合，采用ECHAM6大气环流模型（版本6.3.5p2，doi:10.17617/2.1810480）。其配置基于PMIP4实验，但使用强制大气环流模型而非完全耦合模型。

ModE-Sim最初旨在构成气候重建（现代时期再分析，ModE-RA，可在本项目中的独立实验中找到）的先验状态，该重建使用离线数据同化技术结合ModE-Sim的输出与历史气候信息。然而，超出了其原始用途，ModE-Sim本身可作为研究气候变率的工具，提供了在给定强迫和边界条件下物理上可能的众多气候状态。这可能包括，例如，将内部变率与对外部强迫信号的响应分离，理解遥相关模式，或研究极端事件。

该集合使用观测/重建的强迫和边界条件，同时考虑这些条件的不确定性。对于1420至1850年，我们提供了60个成员的集合，分为三个子集，使用SST和海冰重建作为边界条件。其中两个子集使用PMIP4辐射强迫，而第三个子集使用来自易火山气溶胶（EVA）模型的20个成员的扰动火山强迫集合，以考虑火山爆发强度和时机的的不确定性。对于1850至2009年，ModE-Sim提供36个成员的集合，分为两个子集，所有子集均使用PMIP4辐射强迫。在海洋边界条件下，20个模拟使用不同的HadISST2实现，而剩余的16个成员使用后者的线性组合。

ModE-Sim的参考文献：
Hand, Ralf; Samakinwa, Eric; Lipfert, Laura; Brönnimann, Stefan. (2023). ModE-Sim – 一个中等规模的大气环流模型（AGCM）集合，用于研究现代时期（1420至2009年）的气候变率。doi:10.5194/gmd-16-4853-2023