Decadal modulation of El Nino Southern Oscillation and its global impacts

厄尔尼诺南方涛动的年代际调制及其全球影响

• 批准号: 2743360
• 金额: --
• 依托单位: University of Leeds
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2743360
• 关键词: Decadal; modulation; El; Nino; Southern

This project will investigate the coupling between modes of climate variability and their effects on seasonal-to-decadal forecast skill. Teleconnections describe interconnections between climate anomalies at distant locations across Earth. Teleconnections frequently arise through the response of atmospheric circulation to changing oceanic conditions. If these patterns can be accurately forecast, the signals provide a major source of predictive skill in seasonal-to-decadal forecasts (Scaife et al., 2016). Hence, there is a need to identify predictable climate signals and understand their effect on the risk of global climate hazards to improve seasonal-to-decadal predictions.Most previous research has considered teleconnections arising from modes of variability separately. However, there is growing evidence for coupling between modes of variability and their teleconnections on different timescales (Cai et al., 2019). Some recent studies have speculated Atlantic Multidecadal Variability - a fluctuating pattern in the North Atlantic ocean -- augments the response of the winter North Atlantic Oscillation to El Nino Southern Oscillation, the dominant pattern of year-to-year variability in the tropics, ENSO is a key driver of the NAO and this teleconnection is important for seasonal forecasting of European winter climate. However, questions remain about whether the AMV modulation of the ENSO-NAO teleconnection is robust and whether it can be distinguished from a local AMV impact on the NAO (Simpson et al., 2018). This PhD project will develop a new framework for assessing the AMV influence on the ENSO-NAO teleconnection using state-of-the-art large ensemble climate simulations. This will provide the most comprehensive assessment to date of decadal modulation of ENSO-NAO coupling by the AMV.Another major research topic has been how ENSO affects climate in remote regions, including the North Atlantic. Few studies have considered teleconnections that alter ENSO itself. Recent work at the University of Leeds suggests the warm phase of AMV weakens ENSO on decadal timescales. This project will test this effect in a larger set of climate models and identify whether it is robustly simulated. New model simulations will also be performed to test hypotheses and isolate mechanisms. These experiments will exploit new 'nudging' capabilities within a climate model that enable specified regions to be constrained to observations to isolate remote impacts.To close the loop on Pacific-Atlantic interactions, the third question addressed in the project will be: what are the impacts of the North Atlantic Oscillation on ENSO? The motivation comes from the observation that on seasonal timescales the NAO drives a tripolar pattern in North Atlantic sea surface temperatures through modified air-sea coupling. This raises the potential for longer-term multidecadal NAO trends to impact on climate outside the North Atlantic, but this is currently unexplored. This project will tackle this new question using a combination of statistical analysis of observations and a similar model experiment design where NAO anomalies are 'nudged' and the global response evolves.The specific objectives of the project will be adapted to fit the interests of the student and to pursue the most promising avenues of enquiry. Specific research objectives could include:Quantify how Atlantic Multidecadal Variability affects the ENSO-NAO relationship including the associated mechanisms; test whether this is robust in climate models.Explore the impact of the AMV on ENSO and its mechanisms via Atlantic-Pacific interactions.Investigate the global impacts of interannual to decadal NAO variability, including potential impacts on ENSO.

该项目将研究气候变化模式之间的耦合及其对季节到十年预报技能的影响。遥相关描述了地球上遥远地点的气候异常之间的相互联系。遥相关经常通过大气环流对海洋条件变化的响应而产生。如果这些模式能够被准确预测，这些信号就可以为季节到年代际预测提供预测技能的主要来源（Scaife et al., 2016）。因此，有必要识别可预测的气候信号并了解它们对全球气候灾害风险的影响，以改进季节到年代际的预测。大多数先前的研究都单独考虑了由变异模式引起的遥相关。然而，越来越多的证据表明变异模式与其在不同时间尺度上的遥相关之间存在耦合（Cai et al., 2019）。最近的一些研究推测，大西洋多年代变率（北大西洋的一种波动模式）增强了冬季北大西洋涛动对厄尔尼诺南方涛动的响应，而厄尔尼诺南方涛动是热带地区逐年变化的主要模式，ENSO是NAO的关键驱动因素，这种遥相关对于欧洲冬季气候的季节性预报非常重要。然而，关于 ENSO-NAO 遥相关的 AMV 调制是否稳健以及是否可以将其与 NAO 的局部 AMV 影响区分开来的问题仍然存在（Simpson 等，2018）。该博士项目将开发一个新框架，利用最先进的大型集合气候模拟来评估 AMV 对 ENSO-NAO 遥相关的影响。这将提供迄今为止最全面的 AMV 对 ENSO-NAO 耦合的十年调制的评估。另一个主要研究课题是 ENSO 如何影响包括北大西洋在内的偏远地区的气候。很少有研究考虑到遥相关会改变 ENSO 本身。利兹大学最近的研究表明，AMV 的暖期会在十年时间尺度上削弱 ENSO。该项目将在更大的气候模型中测试这种效应，并确定其模拟是否可靠。还将进行新的模型模拟来测试假设并隔离机制。这些实验将利用气候模型中新的“推动”功能，使特定区域能够仅限于观测，以隔离远程影响。为了闭合太平洋-大西洋相互作用的循环，该项目解决的第三个问题将是：北大西洋涛动对 ENSO 的影响是什么？其动机来自于这样的观察：在季节性时间尺度上，NAO 通过改进的海气耦合驱动北大西洋海面温度的三极模式。这增加了长期的数十年 NAO 趋势对北大西洋以外气候影响的可能性，但目前尚未对此进行探索。该项目将结合观测统计分析和类似的模型实验设计来解决这个新问题，其中“推动”NAO 异常并不断发展全球响应。该项目的具体目标将适应学生的兴趣，并寻求最有希望的探究途径。具体的研究目标可能包括：量化大西洋多年代变率如何影响 ENSO-NAO 关系，包括相关机制；测试这在气候模型中是否稳健。通过大西洋-太平洋相互作用探索 AMV 对 ENSO 的影响及其机制。研究年际到十年间 NAO 变化的全球影响，包括对 ENSO 的潜在影响。