Collaborative Research: Forced Trends in the Tropical Pacific and Global Tropical Cyclones

合作研究：热带太平洋和全球热带气旋的强迫趋势

• 批准号: 2217619
• 负责人: Boniface Fosu
• 金额: $ 4.14万
• 依托单位: Mississippi State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-01 至 2025-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217619&HistoricalAwards=false
• 关键词: Collaborative; Research; Forced; Trends; Tropical

The temperature contrast between the "warm pool" region of the western equatorial Pacific and the "cold tongue" in the east is remarkable: visitors to the Solomon islands find sea surface temperatures (SSTs) above 80F while visitors to the Galapagos don wetsuits to go snorkeling. Naturally the temperature contrast has a variety of effects on the weather and climate of the tropics, one of which is the relative abundance of hurricanes (also called typhoons and TCs, for tropical cyclones) which are more abundant in the western Pacific than anywhere else in the world. The influence of the SST contrast can be seen in comparisons between El Nino events, in which the contrast weakens due to warming in the cold tongue region, and La Nina events, which strengthen the contrast. El Nino years feature fewer TCs in the western Pacific and more in the central and eastern Pacific, with the opposite pattern in La Nina years.The influence of El Nino and La Nina on TCs and other aspects of tropical weather and climate begs the question: will the equatorial Pacific SST contrast be strengthened or weakened by greenhouse gas-induced global warming? The evidence is mixed since climate models generally show weakening as the earth warms but observations show strengthening over the past few decades. The mismatch could be due to the internal variability of the climate system, which operates even as greenhouse gas increases warm the world. But it is also possible that climate model biases, in particular the bias of a cold tongue which is too cold and too extensive, lead to incorrect simulations of the effects of greenhouse warming.Work under this award addresses the possible effect of the cold tongue bias on the simulated SST contrast change using a technique called flux adjustment, in which the exchange of heat and moisture between the atmosphere and ocean is modified to eliminate the cold tongue bias in present-day climate simulations. The flux-adjusted climate model is then used to simulate the response of the SST contrast to greenhouse gas increases. The work is carried out with the Community Earth System Model version 2 (CESM2).The effects of an El Nino-like or La Nina-like SST warming pattern on tropical cyclones is difficult to assess from climate model simulations because the resolution of climate models is not typically high enough to simulate TCs. One strategy pursued here is to simulate TCs using shorter simulations from a high-resolution atmosphere-only model which is run over the SST warming pattern produced by the climate model. Another is to use the Columbia HAZard model (CHAZ), an empirical TC model developed by the lead Principal Investigator (PI). CHAZ uses large-scale atmospheric conditions from the climate model or observational datasets to predict the tracks and intensities of "synthetic" TCs that are initiated at random based on a TC genesis index.The work has societal as well as scientific value given the consequences of warming-induced changes in TC behavior. It is clear that warming causes the most intense hurricanes to become stronger and more destructive, thus efforts to anticipate changes in the distribution of TCs across the Pacific are valuable for climate adaptation and disaster risk reduction. The PIs have strong ties to the World Bank, the reinsurance industry, and other relevant stakeholders through the Columbia World project. They also conduct extensive media outreach on climate change-related topics including TC risk. In addition, the project supports a postdoctoral fellow and a graduate student, thereby promoting the future workforce in this research area.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.

赤道西太平洋的“暖池”地区与东部的“冷舌”地区之间的温度对比非常显着：前往所罗门群岛的游客发现海面温度（SST）超过 80 华氏度，而前往加拉帕戈斯群岛的游客则穿着潜水服前往浮潜。当然，温度对比对热带地区的天气和气候有多种影响，其中之一是飓风（也称为台风和热带气旋）的相对丰富，西太平洋地区比其他任何地方都更加丰富。世界。 海温对比的影响可以通过厄尔尼诺事件和拉尼娜事件的对比看出，厄尔尼诺事件的对比因冷舌区变暖而减弱，而拉尼娜事件的对比则增强。 厄尔尼诺年西太平洋热带气旋较少，中太平洋和东太平洋热带气旋较多，而拉尼娜年则相反。厄尔尼诺和拉尼娜年对热带气旋和热带天气气候其他方面的影响引出了一个问题：赤道太平洋海温对比会因温室气体引起的全球变暖而增强还是减弱？ 证据好坏参半，因为气候模型通常显示随着地球变暖而减弱，但观测显示过去几十年来增强。 这种不匹配可能是由于气候系统的内部变化造成的，即使温室气体增加导致世界变暖，气候系统仍然在运行。但气候模型的偏差，特别是太冷和太广泛的冷舌偏差，也有可能导致对温室变暖影响的错误模拟。该奖项下的工作解决了冷舌偏差可能产生的影响使用称为通量调整的技术来模拟海温对比变化，其中修改大气和海洋之间的热量和水分交换，以消除当今气候模拟中的冷舌偏差。 然后使用通量调整气候模型来模拟海温对比对温室气体增加的响应。这项工作是通过社区地球系统模型版本 2 (CESM2) 进行的。类厄尔尼诺或类拉尼娜海温变暖模式对热带气旋的影响很难通过气候模型模拟来评估，因为气候模型的分辨率通常不够高，无法模拟 TC。 这里采取的一项策略是使用高分辨率纯大气模型的较短模拟来模拟TC，该模型在气候模型产生的海表温度变暖模式上运行。 另一种方法是使用哥伦比亚 HAZard 模型 (CHAZ)，这是由首席研究员 (PI) 开发的经验 TC 模型。 CHAZ 使用气候模型或观测数据集中的大尺度大气条件来预测基于 TC 成因指数随机启动的“合成”TC 的轨迹和强度。鉴于以下后果，这项工作具有社会和科学价值：变暖引起的 TC 行为变化。 显然，变暖会导致最强烈的飓风变得更强、更具破坏性，因此预测太平洋地区热带气旋分布变化的努力对于气候适应和减少灾害风险很有价值。 PI 通过哥伦比亚世界项目与世界银行、再保险行业和其他相关利益相关者有着密切的联系。 他们还就包括热带气旋风险在内的气候变化相关话题开展广泛的媒体宣传。 此外，该项目还支持一名博士后研究员和一名研究生，从而促进该研究领域的未来劳动力。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。