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: 2217620
• 负责人: Kevin Reed
• 金额: $ 8.13万
• 依托单位: SUNY at Stony Brook
• 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=2217620&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.

赤道太平洋西部的"暖池"区域和东部的"冷舌"区域之间的温度对比是显著的：前往所罗门群岛的游客发现海面温度（SST）高于80华氏度，而前往加拉帕戈斯的游客则穿上潜水服去浮潜。自然地，温度对比对热带地区的天气和气候有各种影响，其中之一是飓风（也称为台风和TC，用于热带气旋）的相对丰富，西太平洋比世界上任何其他地方都要丰富。 SST对比度的影响可以在厄尔尼诺事件和拉尼娜事件之间的比较中看到，在厄尔尼诺事件中，对比度由于冷舌区域的变暖而减弱，拉尼娜事件加强了对比度。 El Nino年西太平洋热带气旋相对较少，中、东太平洋热带气旋相对较多，而La Nina年则相反。El Nino和La Nina对热带气旋及其他热带天气气候的影响引发了一个问题：温室气体引起的全球变暖会加强还是削弱赤道太平洋海温的对比度？ 证据是混合的，因为气候模型通常显示随着地球变暖而减弱，但观测显示在过去几十年中加强。 这种不匹配可能是由于气候系统的内部可变性，即使温室气体增加使世界变暖，气候系统也在运作。但气候模型的偏差，特别是太冷、太广泛的冷舌的偏差，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对模拟的SST对比度变化的可能影响使用一种称为通量调整的技术，其中修改了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。 通量调整的气候模式，然后用来模拟的SST对比温室气体增加的反应。这项工作是在共同体地球系统模式第二版（CESM2）下进行的。由于气候模式的分辨率通常不足以模拟热带气旋，因此很难从气候模式模拟中评估厄尔尼诺或拉尼娜等SST变暖模式对热带气旋的影响。 这里采用的一种策略是使用来自高分辨率大气模式的较短模拟来模拟TC，该模式运行在气候模式产生的SST变暖模式上。 另一种方法是使用哥伦比亚危险模型（CHAZ），这是一种由首席研究员（PI）开发的经验TC模型。 CHAZ使用气候模式或观测数据集的大尺度大气条件，根据TC成因指数预测随机启动的"合成" TC的轨迹和强度。考虑到变暖引起的TC行为变化的后果，这项工作具有社会和科学价值。 很明显，气候变暖会导致最强烈的飓风变得更强，更具破坏性，因此，预测热带气旋在整个太平洋的分布变化对于适应气候变化和减少灾害风险是很有价值的。 通过哥伦比亚世界项目，参与者与世界银行、再保险业和其他相关利益攸关方有着密切的联系。 他们还就气候变化相关议题，包括TC风险，开展广泛的媒体宣传。 此外，该项目还支持一名博士后和一名研究生，从而促进了该研究领域未来的劳动力。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。