Effects of rapid Arctic climate change on jet streams and extreme weather (Ref 4606)

北极气候快速变化对急流和极端天气的影响（参考文献 4606）

• 批准号: 2859553
• 金额: --
• 依托单位: UNIVERSITY OF EXETER
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2859553
• 关键词: Effects; rapid; Arctic; climate; change

Project BackgroundThe lower atmospheric warming as a result of manmade CO2 emissions is several times larger in the Arctic than in other parts of the world (see figure 1), a phenomenon known as Arctic Amplification. The importance of this amplified warming could extend well beyond the Arctic, however. The midlatitude jet streams (figure 2), and their associated storm tracks, are effectively powered by the temperature difference between the warmer low latitudes and the colder high latitudes. Arctic amplification decreases this temperature gradient in the lowermost atmosphere, potentially impacting the jet stream and storms. Such changes could lead to an increase in extreme weather, which is a particular concern for the lives and livelihoods of the billions of people who live under the path of the jet stream [e.g., Cohen et al., 2014]. Arctic amplification is a robust phenomenon that appears clearly in state-of-the art climate models, and is relatively well understood. However, the response of the jet stream to Arctic amplification is far more uncertain, and varies substantially between different climate model experiments (Screen et al., 2018; Screen and Blackport, 2019). Until we better understand the ways that the jet stream is affected by Arctic amplification, we cannot skilfully predict future changes in extreme weather, which is a significant problem. This lack of a robust jet stream response across models may reflect differences in how they simulate the present-day climate. For example, the average location of the jet stream is further north in some models than others, which might affect how strongly the jet stream is affected by Arctic amplification in a one model compared to another (Smith et al., 2017). In addition, Arctic amplification occurs alongside other robust features of climate change, including the tropical upper-tropospheric warming that will also influence the behaviour of the midlatitude jet. Understanding how these processes interact, and what their combined effect is on the jet stream is of significant interest. By understanding what causes models to differ, we seek to reduce uncertainty in future projections of midlatitude climate and extreme weather.Project Aims and MethodsWe will conduct experiments using a new, relatively simple but highly configurable global climate model known as Isca, developed by Dr Thomson and others at Exeter (execlim.github.io/IscaWebsite/). Isca has the ability, unlike most climate models, to be able to turn relevant processes on and off, and to 'nudge' the atmosphere to different background states. By using these features, we can investigate how jet stream responds to Arctic amplification in a controlled manner, and ascertain which processes are the most important. We will also make use of output of new experiments already run using sophisticated climate models as part of the Polar Amplification Model Intercomparison Project (PAMIP; Smith et al., 2019) lead by Dr Smith and Prof Screen. We will combine the data from PAMIP and results from more traditional all-forcing experiments from CMIP6, as well as results from Isca to understand better how biases in present day climate can influence predictions of jet stream properties, and the impacts on extreme weather.

项目背景在北极的人造二氧化碳排放导致的下部大气变暖比世界其他地区大几倍（见图1），这是一种称为北极扩增的现象。但是，这种放大变暖的重要性可能远远超出了北极。中纬度喷气流（图2）及其相关的风暴轨迹有效地由温暖的低纬度和较冷的高纬度之间的温度差。北极扩增可在最低的大气中降低该温度梯度，从而可能影响喷气流和风暴。这种变化可能导致极端天气的增加，这特别关心生活在喷气流道路下的数十亿人的生活和生计[例如，Cohen等，2014]。北极扩增是一种强大的现象，在最先进的气候模型中显然出现，并且相对理解。但是，喷气流对北极扩增的响应更加不确定，并且在不同的气候模型实验之间有很大的变化（Screen等，2018； Screen and Blackport，2019）。除非我们更好地了解喷气流受北极扩增的影响，否则我们无法巧妙地预测极端天气的未来变化，这是一个重大问题。在模型之间缺乏强大的喷射流响应可能反映了它们模拟当今气候的差异。例如，在某些模型中，喷气流的平均位置比其他模型更北，这可能会影响喷气流与另一种模型相比，在一个模型中受到北极扩增的强烈影响（Smith等，2017）。此外，北极扩增发生在气候变化的其他鲁棒特征的同时，包括热带上流层变暖，这也将影响中纬度射流的行为。了解这些过程的相互作用方式及其对喷气流的综合效应是重要的。通过了解导致模型有所不同的原因，我们试图减少中纬度气候和极端天气的未来预测的不确定性。项目的目标和方法将使用一种新的，相对简单但相对简单但可配置高度可配置的全球气候模型，由Thomson Dr Dr Dr和其他在Exeter上开发的全球气候模型，Exetlim.github.gitlim.github.io.io.io/iscaweebite/）。与大多数气候模型不同，ISCA具有能够打开和关闭相关过程，并将气氛“推动”到不同背景状态的能力。通过使用这些功能，我们可以研究喷气流以受控方式对北极扩增的反应，并确定哪些过程是最重要的。我们还将利用已经使用复杂的气候模型作为极地放大模型比较项目的一部分（Pamip; Smith等，2019）的新实验的输出来运行。我们将结合PAMIP的数据，以及来自CMIP6的更传统的全努力实验的结果，以及ISCA的结果，以更好地了解当今气候下的偏见如何影响喷气流性质的预测以及对极端天气的影响。