Modulation of El Niño Southern Oscillation and its impacts by the mean climate state

厄尔尼诺南方涛动的调节及其平均气候状态的影响

• 批准号: 2296358
• 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: 2019
• 资助国家: 英国
• 起止时间: 2019 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2296358
• 关键词: Modulation; El; Ni; Southern; Oscillation

The El Niño Southern Oscillation (ENSO) is the leading mode of interannual climate variability in the tropics and affects regional climates around the globe. During ENSO events, changes to atmospheric circulation and precipitation patterns in response to perturbed sea surface temperature lead to remote climate effects that vary regionally and by season. Internal modes of interannual climate variability such as the Pacific Decadal Oscillation (PDO) and the Atlantic multidecadal variability (AMV), along with anthropogenic sources of radiative forcing (eg. greenhouse gases emission and aerosol concentration) alter the global climate circulation on interannual and decadal timescales and therefore must be included in the study of ENSO impacts under future climate conditions.A largely unexplored research area is whether the effects of ENSO events on climate extremes may change in a future, warmer climate. Climate change may affect both the frequency of climate extremes, increasing the variance, and the mean, changing the shape of the distribution of a certain variable in the future (Lavell et al., 2012). In a warmer climate, the increase in atmospheric moisture may intensify the variability in precipitation associated with ENSO (Christensen et al., 2013). However, generally few attempts have been made to examine the specific contribution of ENSO to changing extremes. The latest climate model simulations encompassed in the Climate Model Intercomparison Model Phase 6 (CMIP6) will mean significant improvements in the representation of ENSO (Collins et al., 2014). A especial focus of the project will be on evaluating the influence of the North Atlantic mean state on ENSO and its climate impacts. This will be addressed by contrasting ENSO impacts between simulations in which the North Atlantic SST will be constraint to warm or cold conditions. Recent literature suggests that Atlantic multidecadal variability (AMV) can modify the tropical Pacific mean state (McGregor et al., 2014, Li et al., 2016, Ruprich-Robert et al., 2017). However, it is still not clear how those changes in the Pacific mean state translate into changes of ENSO behaviours (e.g. Wang et al., 2017). In addition, recent studies suggested that the AMV can also influence ENSO teleconnections even without changing ENSO itself (Lopez-Parages et al., 2015). A better understanding of the AMV influences on ENSO and its teleconnections will increase the level of confidence of extreme impacts assessments and seasonal forecasts.The specific objectives of the project are: 1. Investigate ENSO and its impacts from different model resolutions. In particular, contrasting these in low and high resolution simulations, including those performed within the High Resolution Model Intercomparison project (HighResMIP) and other very high resolution simulations performed by BSC. This approach represents a great advantage in terms of high-resolution runs that will allow to assess small-scale climate impacts.2. Evaluate the influence of different mean states on ENSO and its impacts (including precipitation and temperature extremes) by comparing simulated ENSO impacts from present day with end of 21th century simulations.3. Assess ENSO impacts with different North Atlantic background conditions using the Decadal Climate Prediction Project (DCPP) Component C experiments of CMIP6.4. Determine relationships between ENSO and different anthropogenic forcing levels from step change perturbation experiments.5. Determine the most vulnerable regions to future ENSO events and make an impact assessment of extremes.

厄尔尼诺南方涛动(ENSO)是热带地区年际气候变化的主要模式，影响着全球的区域气候。在ENSO事件期间，大气环流和降水模式因扰动的海面温度而发生变化，从而导致区域和季节不同的远程气候影响。年际气候变率的内部模式，如太平洋年代际涛动(PDO)和大西洋年代际变率(AMV)，以及辐射强迫的人为来源(例如。温室气体排放和气溶胶浓度)在年际和年代际时间尺度上改变了全球气候环流，因此必须包括在未来气候条件下的ENSO影响的研究中。一个基本上未被探索的研究领域是，ENSO事件对气候极端事件的影响是否会在未来更温暖的气候中发生变化。气候变化可能既影响极端气候事件的频率，增加方差，又影响平均值，从而改变未来某一变量的分布形态(Lavell等人，2012年)。在气候变暖的情况下，大气湿度的增加可能会加剧与ENSO有关的降水变化(Christensen等人，2013年)。然而，通常很少有人尝试研究ENSO对极端气候变化的具体贡献。气候模型对比模式第六阶段(CMIP6)中包含的最新气候模型模拟将意味着ENSO的表示有重大改进(Collins等人，2014年)。该项目的一个特别重点将是评估北大西洋平均状态对ENSO的影响及其气候影响。这将通过对比模拟之间的ENSO影响来解决，在模拟中，北大西洋海温将被限制在温暖或寒冷的条件下。最近的文献表明，大西洋年代际变化(AMV)可以改变热带太平洋平均状态(McGregor等人，2014，Li等人，2016，Ruprich-Robert等人，2017)。然而，目前仍不清楚太平洋平均状态的这些变化如何转化为ENSO行为的变化(例如Wang等人，2017年)。此外，最近的研究表明，即使不改变ENSO本身，AMV也可以影响ENSO遥相关(Lopez-Parages等人，2015年)。更好地了解AMV对ENSO及其遥相关的影响，将提高极端影响评估和季节预报的置信度。本项目的具体目标是：1.从不同模式分辨率调查ENSO及其影响。特别是，在低分辨率和高分辨率模拟中进行对比，包括在高分辨率模型对比项目(HighResMIP)内执行的模拟和由BSC执行的其他非常高分辨率的模拟。这种方法在高分辨率运行方面是一个巨大的优势，这将允许评估小规模气候影响。通过比较今天和21世纪末模拟的ENSO影响，评估不同平均态对ENSO及其影响(包括降水和温度极值)的影响。利用CMIP6.4的十年气候预测项目(DCPP)C部分实验，评估不同北大西洋背景条件下ENSO的影响。通过阶跃变化扰动实验确定ENSO与不同人为强迫水平之间的关系。确定对未来ENSO事件最脆弱的区域，并对极端事件进行影响评估。