Improved Understanding of the Moist Dynamics of the Extratropical Storm Tracks and Their Response to Climate Change

从根本上说，我们在地图上看到的锋面天气系统可以用斜压不稳定性理论来解释，在斜压不稳定性理论中，小扰动通过从温暖的热带和寒冷的两极之间的温度差异中提取能量而增长。这一理论是可行的，但它忽略了当水蒸气凝结成云和降水时所释放的巨大热量。 假设凝结加热是不稳定的是合理的，但我们对它对天气系统的增长率，传播速度，降水强度和其他方面的影响的理解是非常有限的。凝结加热的作用是一个实际问题，因为大气中的水蒸气量随温度增加而增加，因此人们可能会期望随着气候变暖而产生更强烈的降水和更强的风暴。该奖项的工作旨在为凝结加热对斜压不稳定性的影响以及这些影响对全球温度的依赖性提供理论基础。这项研究的一个目标是非绝热罗斯比涡旋（DRV，也称为非绝热罗斯比波），这是一种相对较小规模的天气系统，由凝结加热推动，传播迅速，可以迅速增强为强大的风暴。 DRV最初是在简化的模型模拟中发现的，但现在已经与1999年冬季风暴洛萨（Lothar）等严重风暴的发展有关，这是几十年来袭击西欧最具破坏性的风暴之一。 一个更理论性的问题是凝结加热对最不稳定的斜压模态的影响，这意味着对于给定的中纬度温度对比及其伴随的高层急流，槽和脊的模式增长最快。 首席研究员和其他人的早期工作表明，冷凝加热导致模式中向上运动的区域收缩，并且相对于向下运动的区域变得更加强烈。 上升气流区域的变窄和增强非常重要，因为它增加了极端降水的可能性。这项工作具有社会意义，因为它关注天气系统的强度，它们产生的降水强度，以及温度升高导致更具破坏性的风暴的程度。 该项目还为研究生提供支持和培训，从而为该研究领域的未来劳动力做出贡献。 此外，首席研究员还担任麻省理工学院夏季研究计划的教师导师，该计划旨在提高来自服务不足的少数群体的本科生在科学和工程领域的参与度。该奖项反映了NSF的法定使命，并被认为值得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来支持。

At a fundamental level the frontal weather systems we see on maps can be explained by the theory of baroclinic instability, in which small disturbances grow by extracting energy from the temperature contrast between the warm tropics and the cold poles. The theory works but it neglects the enormous heat release that occurs when water vapor condenses to form clouds and precipitation. It is reasonable to assume that condensational heating is destabilizing but our understanding of its effects on the growth rate, propagation speed, precipitation intensity, and other aspects of weather systems is quite limited. The role of condensational heating is a practical concern as the amount of water vapor in the atmosphere increases with temperature, thus one might expect more intense precipitation and stronger storms as climate warms.Work under this award seeks to develop a theoretical basis for the effects of condensational heating on baroclinic instability and the dependence of these effects on global temperature. One target of the study is diabatic Rossby vortices (DRVs, also called diabatic Rossby waves), which are relatively small-scale weather systems fueled by condensational heating which propagate quickly and can intensify rapidly into powerful storms. DRVs were first identified in simplified model simulations but have now been implicated in the development of severe storms like winter storm Lothar in 1999, among the most destructive to hit western Europe in several decades. A more theoretical concern is the effect of condensational heating on the most unstable baroclinic mode, meaning the pattern of troughs and ridges that grows most rapidly for a given middle-latitude temperature contrast and its accompanying upper-level jet stream. Earlier work by the Principal Investigator and others shows that condensational heating causes the regions of upward motion in the mode to contract and become more intense relative to the regions of downward motion. The narrowing and intensification of the updraft regions is important as it increases the likelihood of extreme precipitation.The work has societal relevance due to its focus on the strength of weather systems, the intensity of precipitation they generate, and the extent to which warmer temperatures lead to more destructive storms. The project also provides support and training to a graduate student, thereby contributing to the future workforce in this research area. In addition, the Principal Investigator serves as a faculty mentor in the MIT Summer Research Program, which seeks to increase the engagement of undergraduate students from underserved minority groups in science and engineering.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.