Collaborative Research: El Nino/Southern Oscillation (ENSO) Predictability--Initial Condition Signal versus Uncoupled Atmospheric Noise

合作研究：厄尔尼诺/南方涛动 (ENSO) 可预测性 - 初始条件信号与非耦合大气噪声

• 批准号: 2241538
• 负责人: Benjamin Kirtman
• 金额: $ 70.85万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-06-01 至 2027-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2241538&HistoricalAwards=false
• 关键词: Collaborative; Research; El; Nino; Southern

The equatorial Pacific has an outsized influence on weather and climate as it is home to the El Nino/Southern Oscillation (ENSO) phenomenon, featuring an alternation between warm equatorial sea surface temperatures (SSTs) during El Nino events and cold SSTs during La Nina events. These SST changes affect the global atmospheric circulation and thus induce long-range impacts including changes in the severity of winters in Canada, the distribution of rainfall in the Asian monsoon, and Atlantic hurricane activity. These worldwide impacts have motivated intensive efforts to develop ENSO prediction systems, which show some promise but so far have had mixed results.Here the PIs hypothesize that the mixed success of ENSO predictions is intrinsic to ENSO, meaning that some ENSO events are in fact more predictable than others. In that case a "forecast of the forecast skill", meaning a method to determine in advance the likely accuracy of an ENSO prediction, would have great practical value. The Principal Investigators (PIs) are particularly concerned with the skill of ENSO predictions made before the onset of the event, which are skillful to the extent that ENSO events develop from some form of preconditioning such as the buildup of heat in the subsurface equatorial ocean. Model simulations conducted previously by the PIs suggest that preconditioning is not a necessary condition for ENSO events, which can initiate rapidly starting from neutral conditions. Such events, arising purely from the chaotic growth of very small initial perturbations of the atmosphere-ocean system, would be inherently unpredictable. But the PIs argue that some forms of preconditioning can render the system less susceptible to noise-level perturbations and instead drive the evolution of an El Nino or La Nina event in a deterministic manner, allowing skillful predictions several months ahead of the onset.The PIs test their hypothesis through numerical simulations performed with the Community Earth System Model (CESM). The work takes advantage of procedures they have developed for strictly controlling the state of the equatorial Pacific in CESM simulations, so that various forms of preconditioning can be imposed or excluded. Additional work uses the PI's Interactive Ensemble (IE) technique (see for example AGS-1558837) to consider the role of random weather fluctuations unrelated to ENSO in limiting the predictability of ENSO events.The work is of societal as well as scientific interest given the global impacts of ENSO events, and results of this research have direct bearing on attempts to improve ENSO forecasts. The software developed for the project is made available to the research community, along with relevant datasets, to facilitate adoption of methods and results by the research and operational communities. In addition, the PIs participate in summer internship programs targeting high school and college students through Miami-Dade College and the American Indian Higher Education Consortium.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

赤道太平洋对天气和气候的影响非常大，因为它是厄尔尼诺/南方涛动(ENSO)现象的发源地，其特征是厄尔尼诺事件期间赤道海温(SST)的暖和拉尼娜事件期间的冷SST之间的交替。这些海温变化影响全球大气环流，从而引起长期影响，包括加拿大冬季严酷程度、亚洲季风降雨分布和大西洋飓风活动的变化。这些全球范围的影响促使人们加紧努力开发ENSO预测系统，这些系统显示出一些希望，但到目前为止结果喜忧参半。这里，PI假设ENSO预测的混合成功是ENSO固有的，这意味着一些ENSO事件实际上比其他事件更可预测。在这种情况下，“预报技巧的预报”，即预先确定ENSO预报的可能准确度的方法，将具有很大的实用价值。首席调查员特别关注在事件发生前作出的ENSO预测的技巧，因为ENSO事件是从某种形式的预条件发展而来的，例如赤道次表层海洋中的热量积累。PI以前进行的模式模拟表明，预条件不是ENSO事件的必要条件，ENSO事件可以从中性条件快速启动。这类事件纯粹是由大气-海洋系统非常小的初始扰动的混乱增长引起的，本质上是不可预测的。但私人投资者认为，某些形式的预适应可以使系统不太容易受到噪音水平扰动的影响，相反，它会以确定性的方式推动厄尔尼诺或拉尼娜事件的演变，使人们能够在厄尔尼诺或拉尼娜事件发生前几个月进行巧妙的预测。私人投资者通过使用社区地球系统模型(CESM)进行的数值模拟来验证他们的假设。这项工作利用了他们为在CESM模拟中严格控制赤道太平洋状态而开发的程序，以便可以施加或排除各种形式的预条件。其他工作使用PI的交互集合(IE)技术(例如见AGS-1558837)来考虑与ENSO无关的随机天气波动在限制ENSO事件的可预报性方面的作用。鉴于ENSO事件的全球影响，这项工作具有社会和科学意义，而这项研究的结果直接影响到改善ENSO预测的尝试。为该项目开发的软件连同相关数据集一起提供给研究界，以便利研究界和业务界采用方法和结果。此外，PIs还通过迈阿密-戴德学院和美国印第安人高等教育协会参与针对高中生和大学生的暑期实习计划。这一奖励反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。