Improving simple climate models through a traceable and process-based analysis of ocean heat uptake in AOGCMs and observations

通过对 AOGCM 和观测中的海洋吸热进行可追溯和基于过程的分析，改进简单的气候模型

• 批准号: NE/K016083/1
• 负责人: Remi Tailleux
• 金额: $ 46.89万
• 依托单位: University of Reading
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK016083%2F1
• 关键词: Improving; simple; climate; models; through

Future climate change predictions provide essential guidance for the global efforts to curb the global warming trend caused by human emissions of greenhouse gases. The main tool to provide these projections are coupled atmosphere-ocean general circulation models (AOGCMs). However, these models are computationally still very expensive to run. Therefore, simple climate models (SCMs) have been developed, which are able to mimic the climate response seen in the AOGCMs, but at a much reduced computational cost. SCMs are being used for several purposes, e.g. simulating how the projections depend on key climate parameters, or for the interpretation of the AOGCM projections. SCMs are often used for policy advice.To ascertain the usefulness and accuracy of SCMs, it is essential to establish their traceability to comprehensive AOGCMs and ultimately to reality. The link and hence the traceability between SCMs, AOGCMs and observations is established through the process of calibration, which is the key step whereby the values of the control parameters of a given model are set up. There appear to be two main kinds of calibration: physical and behavioural, which operate very differently. A physical calibration is one that specifies the control parameters of a given model by invoking physical arguments or observational constraints on the physical processes involved. In contrast, a behavioural calibration is one that specifies the same control parameters so that the model reproduces various emergent properties of the actual or simulated climate system, under past, present or future conditions. Because climate change is primarily controlled by ocean heat uptake (OHU), the accuracy of climate change projections depends on the validity of the representation of the physical processes controlling OHU in SCMs and AOGCMs. How these processes are represented varies widely across SCMs, and ranges from explicit to entirely implicit representations. In this project, three specific SCMs are considered. In MAGICC, ocean heat uptake is explicitly represented through two vertical advection/diffusion equations for each hemisphere. In Gregory (2000)'s two-layer model, it is represented via two simple ordinary differential equations with two-time scales. In Good et al. (2011,2012)'s step-response approach, ocean heat uptake is entirely implicit. In this proposal, our first objective will be to assess the degree of generality of each SCM by testing their relative performances on the same range of climate change scenarios, in order to identify which simplified representation of OHU performs better. Our second objective will be to investigate the link between physical and behavioural calibration, by implementing a physical calibration of MAGICC, and testing whether it improves or deteriorates its performances and why. This will provide key new insights on which aspects of ocean heat uptake are robust, and which are in need of further study, which will enhance the credibility of SCMs. The first and second objectives address Goal 2 of the Call. Our third objective will be to develop a versatile and flexible approach to constraining ocean heat uptake processes by using NEMO and its adjoint NEMOTAM, allowing for the optimal calibration of mixing parameters from both physical and behavioural constraints. This will endow the UK with a key capability for systematically re-calibrating ocean models by incorporating observational and theoretical advances on ocean mixing processes, and testing the implications for climate change projections. Moreover, the optimisation set-up for NEMO is potentially useful for many other types of studies in the future. This addresses Goal 1 of the Call. This will make a key contribution to the joint NERC-Met Office strategy for the development of UKESM1.

未来气候变化预测为全球遏制人类排放温室气体导致的全球变暖趋势提供重要指导。提供这些预测的主要工具是大气-海洋大气环流耦合模型（AOGCM）。然而，这些模型的运行计算成本仍然非常昂贵。因此，人们开发了简单的气候模型（SCM），它能够模拟 AOGCM 中的气候响应，但计算成本大大降低。 SCM 有多种用途，例如模拟预测如何依赖于关键气候参数，或解释 AOGCM 预测。 SCM 通常用于政策建议。为了确定 SCM 的有用性和准确性，必须建立其对综合 AOGCM 并最终对现实的可追溯性。 SCM、AOGCM 和观测之间的联系以及由此产生的可追溯性是通过校准过程建立的，这是建立给定模型的控制参数值的关键步骤。校准似乎有两种主要类型：物理校准和行为校准，它们的运作方式截然不同。物理校准是通过调用物理参数或对所涉及的物理过程的观察约束来指定给定模型的控制参数的校准。相比之下，行为校准是指定相同控制参数的校准，以便模型在过去、现在或未来条件下再现实际或模拟气候系统的各种突发特性。由于气候变化主要受海洋吸热 (OHU) 控制，因此气候变化预测的准确性取决于 SCM 和 AOGCM 中控制 OHU 的物理过程表示的有效性。这些过程的表示方式在不同的 SCM 中差异很大，范围从显式表示到完全隐式表示。在此项目中，考虑了三个特定的 SCM。在 MAGICC 中，海洋热量吸收通过每个半球的两个垂直平流/扩散方程明确表示。在Gregory (2000)的两层模型中，它通过两个具有两个时间尺度的简单常微分方程来表示。在古德等人。 （2011，2012）的阶跃响应方法，海洋吸热完全是隐式的。在本提案中，我们的第一个目标是通过测试每个 SCM 在相同范围的气候变化情景下的相对性能来评估每个 SCM 的通用程度，以确定 OHU 的哪种简化表示表现更好。我们的第二个目标是通过实施 MAGICC 的物理校准来研究物理校准和行为校准之间的联系，并测试它是否改善或恶化了其性能以及原因。这将为海洋吸热的哪些方面是稳健的以及哪些方面需要进一步研究提供重要的新见解，从而提高 SCM 的可信度。第一个和第二个目标涉及呼吁的目标 2。我们的第三个目标是开发一种通用且灵活的方法，通过使用 NEMO 及其附属的 NEMOTAM 来约束海洋吸热过程，从而可以根据物理和行为约束对混合参数进行最佳校准。这将使英国具备通过结合海洋混合过程的观测和理论进展来系统地重新校准海洋模型的关键能力，并测试对气候变化预测的影响。此外，NEMO 的优化设置可能对未来许多其他类型的研究有用。这解决了本次呼吁的目标 1。这将为 NERC-Met Office 制定 UKESM1 的联合战略做出重要贡献。

项目成果

A new process-based vertical advection/diffusion theoretical model of ocean heat uptake

一种新的基于过程的海洋吸热垂直平流/扩散理论模型

• DOI: http://dx.10.48550/arxiv.1708.02085
• 发表时间: 2017
• 作者: Tailleux R

Observational and energetics constraints on the non-conservation of potential/Conservative Temperature and implications for ocean modelling

对潜在/保守温度不守恒的观测和能量学限制及其对海洋建模的影响

• DOI: http://dx.10.1016/j.ocemod.2015.02.001
• 发表时间: 2015
• 期刊: Ocean Modelling
• 影响因子: 3.2
• 作者: Tailleux R

A traceable physical calibration of the vertical advection-diffusion equation for modeling ocean heat uptake

用于模拟海洋吸热的垂直平流扩散方程的可追踪物理校准

• DOI: http://dx.10.1002/2015gl063383
• 发表时间: 2015
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Huber M

Generalized Patched Potential Density and Thermodynamic Neutral Density: Two New Physically Based Quasi-Neutral Density Variables for Ocean Water Masses Analyses and Circulation Studies

广义补丁势密度和热力学中性密度：用于海水质量分析和循环研究的两个新的基于物理的准中性密度变量

• DOI: http://dx.10.1175/jpo-d-16-0072.1
• 发表时间: 2016
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Tailleux R

Isoneutral control of effective diapycnal mixing in numerical ocean models with neutral rotated diffusion tensors

具有中性旋转扩散张量的数值海洋模型中有效二重混合的等中性控制

• DOI: http://dx.10.5194/os-15-21-2019
• 发表时间: 2019
• 期刊: Ocean Science
• 影响因子: 3.2
• 作者: Hochet A