Improved Understanding of Changes in Convective Available Potential Energy and Links to the Large-scale Circulation

更好地了解对流可用势能的变化以及与大规模环流的联系

• 批准号: 1749986
• 负责人: Paul O'Gorman
• 金额: $ 41.21万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-03-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1749986&HistoricalAwards=false
• 关键词: Improved; Understanding; Changes; Convective; Available

The build-up of a thunderstorm, from scattered popcorn clouds to a dark towering storm cloud, is a common sight on a summer afternoon. The vigorous growth of such clouds is fueled by the convective available potential energy (CAPE) of the atmosphere. Formally CAPE is the amount of work that would be done by the buoyancy force on a saturated plume of air rising through the portion of the atmosphere in which it is lighter than the surrounding air, assuming that no ambient air mixes into the rising plume. Weather forecasters routinely calculate CAPE from atmospheric temperature soundings and use it to predict the likelihood of severe convective storms.Computer simulations of greenhouse-gas induced climate change commonly show large increases of CAPE with global mean temperature, a result which has raised concerns that thunderstorms may become more common or intense as a consequence of climate change. But the reasons why CAPE should increase with global temperature are not clear, and the lack of a theory for the dependence of CAPE on temperature limits confidence in model results.Under previous funding the PI's group developed a simple model which explains the dependence of CAPE on temperature. But the theory assumes that the atmosphere is in a state of radiative-convective equilibrium, a state which approximates the condition of the atmosphere over warm tropical oceans. The theory is compelling as a starting point but cannot be directly applied to understand CAPE change over land or at higher latitudes. Work under this award thus seeks a more general understanding of the relationship between CAPE and global climate, including the effects of large-scale atmospheric circulation. The research is conducted through examination of climate model simulations produced for the Coupled Model Intercomparison Project, combined with experiments using a cloud resolving model on a limited domain to test hypotheses. The role of atmospheric circulation is assessed through calculation and analysis of moist mean available potential energy (MAPE), the maximum amount of kinetic energy that can be reversibly produced from the mean state of the atmosphere by transforming to a lower energy reference state. The MAPE analysis seeks to relate the mean state of the atmosphere in middle and high latitudes to its potential to generate CAPE through large-scale circulations. The impact of land surface conditions on CAPE is another focus of the research, as the strong diurnal cycle of temperature and moisture plays a key role in the development of convection over land. Further work considers the impact of changes in CAPE on the Walker circulation, a large-scale overturning circulation between the western and eastern Pacific.The work has societal as well as scientific value given the damaging effects of convective storms, including hail, lightning, tornados, and flash floods, along with indications that their intensity or frequency of occurrence may increase due to climate change. Results with practical implications are shared with interested parties through workshops and other venues, and research results are incorporated into classroom teaching and other educational activities. In addition, the project provides support and training to a graduate student, thereby providing for the future work force 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.

从散落的爆米花云到黑暗高耸的风暴云，雷暴的积累是夏季的常见景象。大气的对流可用势能（CAPE）助长了这种云的剧烈生长。正式的斗篷是浮力在饱和的空气羽流中所做的工作数量，该空气穿过大气的一部分，其比周围空气更轻，假设没有环境空气混合到上升的羽流中。 天气预报者通常会从大气温度响声中计算出斗篷，并使用它来预测严重的对流风暴的可能性。温室气体诱发的气候变化的计算机模拟通常显示出与全球平均温度的大量增加，这一结果使人们担心thunderstrorm可能会因气候变化而变得更加共同或激烈。 但是，斗篷应随着全球温度增加的原因尚不清楚，并且缺乏依赖斗篷对温度限制模型结果的理论。在先前的资金资金的情况下，PI组开发了一个简单的模型，该模型解释了CAPE对温度的依赖性。 但是该理论假定大气处于辐射感染平衡状态，这种状态近似于温暖的热带海洋的大气状况。 该理论是一个引人注目的起点，但不能直接应用于了解土地或更高纬度的斗篷变化。 因此，根据该奖项的工作寻求对斗篷与全球气候之间关系的更一般的了解，包括大气循环的影响。 这项研究是通过检查为耦合模型对比项目产生的气候模型模拟进行的，并结合了在有限域中使用云解析模型来检验假设的实验。 通过计算和分析潮湿的平均可用势能（MAPE）来评估大气循环的作用，这是可以通过转换为较低能量参考状态，可以从大气的平均状态可逆地产生的最大动能量。 MAPE分析旨在将中间和高纬度的大气状态与通过大规模循环产生斗篷的潜力联系起来。 土地表面条件对斗篷的影响是研究的另一个重点，因为强大的温度和水分昼夜周期在土地上的对流发展中起着关键作用。进一步的工作考虑了斗篷变化对沃克循环的影响，西部和东部太平洋之间的大规模推翻循环。鉴于对流，雷电，闪电，龙卷风和洪水在内的对流风暴的破坏性影响，这项工作具有社会价值和科学价值，以及其强度或频率会导致临时变化。通过研讨会和其他场所与有兴趣的各方分享了具有实际影响的结果，研究结果纳入了课堂教学和其他教育活动中。 此外，该项目为研究生提供了支持和培训，从而为该研究领域提供了未来的劳动力。该奖项反映了NSF的法定任务，并且使用基金会的知识分子优点和更广泛的审查标准，被认为是值得通过评估的支持。

项目成果

Weakening of the Extratropical Storm Tracks in Solar Geoengineering Scenarios

• DOI: 10.1029/2020gl087348
• 发表时间: 2020-06-16
• 期刊: GEOPHYSICAL RESEARCH LETTERS
• 影响因子: 5.2
• 作者: Gertler, Charles G.;O'Gorman, Paul A.;Watanabe, Shingo
• 通讯作者: Watanabe, Shingo

Changing available energy for extratropical cyclones and associated convection in Northern Hemisphere summer

• DOI: 10.1073/pnas.1812312116
• 发表时间: 2019-03-05
• 期刊: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• 影响因子: 11.1
• 作者: Gertler, Charles G.;O'Gorman, Paul A.
• 通讯作者: O'Gorman, Paul A.

Summer‐Winter Contrast in the Response of Precipitation Extremes to Climate Change Over Northern Hemisphere Land

北半球陆地极端降水对气候变化响应的夏冬对比

• DOI: 10.1029/2021gl096531
• 发表时间: 2022
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Williams, Andrew I.;O’Gorman, Paul A.
• 通讯作者: O’Gorman, Paul A.