Overview of the Norwegian Earth System Model (NorESM2) and key climate response of CMIP6 DECK, historical, and scenario simulations
Overview of the Norwegian Earth System Model (NorESM2) and key climate response of CMIP6 DECK, historical, and scenario simulations
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DOI：
10.5194/gmd-13-6165-2020
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发表时间：
2020-12-04
影响因子：
5.1
通讯作者：
Schulz, Michael
中科院分区：
文献类型：
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作者：
Seland, Oyvind;Bentsen, Mats;Schulz, Michael
提出并评价了挪威耦合地球系统模型(NorESM2)的第二个版本。NorESM2基于共同体地球系统模型(CESM2)的第二版，并与CESM2共享计算机代码基础设施和许多地球系统模型组件。然而，NorESM2采用了完全不同的海洋和海洋生物地球化学模型。NorESM2的大气部分(CAM-NOR)包括一个不同的气溶胶物理和化学模块，包括与云和辐射的相互作用；此外，CAM-NOR还包括在局地干湿能量守恒公式、局地和全球角动量守恒以及深层对流和海气通量计算中的改进。NorESM2的地表成分在反照率计算以及陆地和海冰模式中有微小的变化。我们给出了耦合模式比对项目(CMIP6)第六阶段用NorESM2进行的模拟结果。模型使用了两个版本：一个具有较低(类似于2度)的大气-陆地分辨率，另一个具有中等(类似于1度)的大气-陆地分辨率。评估了前工业气候的稳定性和模式对二氧化碳突然和逐渐翻两番的敏感性，以及模式模拟CMIP6强迫下的历史气候的能力。与观测和再分析相比，NorESM2在大多数方面都比以前的NorESM版本有所改进。NorESM2对温室气体强迫的敏感性似乎低于它的前身，在150年的时间框架内，两种分辨率下的平衡气候敏感性估计为2.5K；然而，这一估计值随着时间窗口的增加而增加，平衡时的气候敏感性要高得多。我们还考虑了根据CMIP6定义的情景模型比较项目中选定的共享社会经济路径(SSP)所定义的对未来情景的模型反应。在四种情景(SSP1-2.6、SSP2-4.5、SSP3-7.0和SSP5-8.5)下，与1850-1879年相比，2090-2099年期间的增温在NorESM2-LM达到1.3、2.2、3.0和3.9K，在NorESM-MM达到1.3、2.1、3.1和3.9K，在两个分辨率上都非常相似。NorESM2-LM显示了一个比较令人满意的现代海冰区域演变。在NorESM2-LM中，只有在SSP1-2.6情景中才能避免无冰的北冰洋。
The second version of the coupled Norwegian Earth System Model (NorESM2) is presented and evaluated. NorESM2 is based on the second version of the Community Earth System Model (CESM2) and shares with CESM2 the computer code infrastructure and many Earth system model components. However, NorESM2 employs entirely different ocean and ocean biogeochemistry models. The atmosphere component of NorESM2 (CAM-Nor) includes a different module for aerosol physics and chemistry, including interactions with cloud and radiation; additionally, CAM-Nor includes improvements in the formulation of local dry and moist energy conservation, in local and global angular momentum conservation, and in the computations for deep convection and air-sea fluxes. The surface components of NorESM2 have minor changes in the albedo calculations and to land and sea-ice models.We present results from simulations with NorESM2 that were carried out for the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Two versions of the model are used: one with lower (similar to 2 degrees) atmosphere-land resolution and one with medium (similar to 1 degrees) atmosphere-land resolution. The stability of the pre-industrial climate and the sen- sitivity of the model to abrupt and gradual quadrupling of CO2 are assessed, along with the ability of the model to simulate the historical climate under the CMIP6 forcings. Compared to observations and reanalyses, NorESM2 represents an improvement over previous versions of NorESM in most aspects. NorESM2 appears less sensitive to greenhouse gas forcing than its predecessors, with an estimated equilibrium climate sensitivity of 2.5 K in both resolutions on a 150-year time frame; however, this estimate increases with the time window and the climate sensitivity at equilibration is much higher. We also consider the model response to future scenarios as defined by selected Shared Socioeconomic Pathways (SSPs) from the Scenario Model Intercomparison Project defined under CMIP6. Under the four scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5), the warming in the period 2090-2099 compared to 1850-1879 reaches 1.3, 2.2, 3.0, and 3.9 K in NorESM2-LM, and 1.3, 2.1, 3.1, and 3.9 K in NorESM-MM, robustly similar in both resolutions. NorESM2-LM shows a rather satisfactory evolution of recent sea-ice area. In NorESM2-LM, an ice-free Arctic Ocean is only avoided in the SSP1-2.6 scenario.