Understanding How Latent Heat Release and Cloud Radiative Effects Shape Jet Variability and Jet Shifts Under Climate Change

了解潜热释放和云辐射效应如何影响气候变化下的射流变率和射流变化

• 批准号: 2202991
• 负责人: Nicholas Lutsko
• 金额: $ 79.25万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 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: 2022-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2202991&HistoricalAwards=false
• 关键词: Understanding; How; Latent; Heat; Release

Jets flying over the middle latitudes of either the Northern or Southern Hemisphere commonly encounter eastward winds with speeds over 100 miles per hour, substantially reducing flight times going east. The presence of such strong flow in the upper troposphere exerts a controlling influence on middle latitude weather systems and even subtle changes in the jet streams can be consequential for surface weather. Simulations of climate change due to greenhouse warming typically show shift of the jet streams toward higher latitudes in both hemispheres, and observations show indications that poleward shifting has already occurred. The poleward shift is similar to the unforced natural variability of the longitudinally averaged jet streams, in which north-south shifting is the most prominent mode.Work under this award considers the role of moisture in the natural north-south shifting of the jet streams and their poleward movement in response to greenhouse gas increases. Moisture can affect the mean jet position through the heating that occurs when it condenses to form cloud droplets, and the clouds cause additional heating and cooling through cloud radiative effects (CREs), in particular cooling by reflecting sunlight back to space and warming by the trapping of outgoing longwave radiation. Recent work suggests that CREs play a strong role in the poleward drift of jets found in climate change simulations, but the exact mechanism has not yet been determined and little work has been done on the role of CREs in natural variability. The role of latent heating in the poleward drift is also relatively unexamined, and two recent studies disagree as to whether latent heating reduces or increases the persistence of naturally occurring jet displacements.The research uses a suite of simplified models, in which moist effects can be added in a controlled manner, to study the influence of latent heating and CREs on north-south jet fluctuations and forced poleward drift. A further resource for the work is the archive of model simulations produced for the Clouds On-Off Klimate Intercomparison Experiment (COOKIE), in which comprehensive climate models are integrated with and without CREs.The work has societal relevance given the effects of jet shifts on surface weather, including their role in determining the frequency and severity of extreme events associated with frontal storms and blocking events. The project provides support and training to a graduate student and postdoctoral research associate, thereby developing the scientific workforce in this research area. The project also recruits an undergraduate student each summer through the Scripps Undergraduate Research Fellowship (SURF) program. In addition, the award supports high school science education through the purchase and use of rotating tanks from the DIYnamics Project, which are used for classroom demonstrations of jet streams, cyclones, and other features of the atmospheric circulation.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.

飞越北半球或南半球中纬度地区的喷气式飞机通常会遇到速度超过每小时 100 英里的东风，从而大大缩短向东飞行的时间。对流层上层如此强烈的气流对中纬度天气系统产生控制性影响，甚至急流的细微变化也可能对地表天气产生影响。 对温室变暖引起的气候变化的模拟通常显示，两个半球的急流都向高纬度地区移动，而观测表明，向极地移动已经发生。 向极地移动类似于纵向平均急流的非受迫自然变化，其中南北移动是最突出的模式。该奖项的工作考虑了水分在急流自然南北移动中的作用，以及它们因温室气体增加而向极地移动。 水分会通过凝结形成云滴时产生的热量影响平均射流位置，并且云会通过云辐射效应（CRE）引起额外的加热和冷却，特别是通过将阳光反射回太空来冷却以及通过捕获来加热出射的长波辐射。 最近的研究表明，CRE 在气候变化模拟中发现的急流向极地漂移中发挥着重要作用，但确切的机制尚未确定，并且关于 CRE 在自然变率中的作用的工作也很少。 潜热在向极漂移中的作用也相对未经检验，并且最近的两项研究对于潜热是否会减少或增加自然发生的喷流位移的持续性存在分歧。该研究使用了一套简化模型，其中可以将潮湿效应以受控方式添加，以研究潜热和 CRE 对南北急流波动和强迫向极漂移的影响。 这项工作的另一个资源是为云开-关气候比对实验 (COOKIE) 生成的模型模拟档案，其中综合气候模型在有和没有 CRE 的情况下进行了集成。考虑到喷气机变化对气候的影响，这项工作具有社会相关性。地面天气，包括它们在确定与锋面风暴和阻塞事件相关的极端事件的频率和严重程度方面的作用。 该项目为研究生和博士后研究员提供支持和培训，从而培养该研究领域的科学队伍。 该项目每年夏天还通过斯克里普斯本科生研究奖学金（SURF）计划招募一名本科生。 此外，该奖项还通过购买和使用 DIYnamics 项目的旋转罐来支持高中科学教育，这些旋转罐用于课堂演示急流、旋风和大气环流的其他特征。该奖项反映了 NSF 的法定使命和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，该项目被认为值得支持。