CAREER: Understanding the Transport Circulation of the Troposphere

职业：了解对流层的运输环流

• 批准号: 1349605
• 负责人: Gang Chen
• 金额: $ 75.58万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2017-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1349605&HistoricalAwards=false
• 关键词: CAREER; Understanding; Transport; Circulation; Troposphere

This is a CAREER award in which the research component examines the transport circulation of the atmosphere. Here transport circulation refers to the movement of air masses and atmospheric constituents, including water vapor and chemical tracers which move over long distances before being rained out or removed by chemical reactions. The transport circulation of the atmosphere is of interest for two practical reasons: first, it plays a key role in determining air quality, as local air quality can be affected by pollutants transported from remote sources. Second, the transport of water vapor, energy, and momentum largely determines the evolution of weather patterns. This is true not only for daily weather but also for month-to-month and year-to-year change in weather patterns such as those associated with El Nino events, fluctuations of the jet streams, and global climate change. In the stratosphere the transport circulation determines the distribution of ozone and the size and severity of the ozone hole. In this project the primary focus is on the longitudinally averaged transport circulation in the north-south direction, for example the movement of constituents into and out of the tropics and polar caps, and the extent to which this movement is enhanced or impeded by various dynamical processes. For example, to what extent do the midlatitude jet streams constitute a mixing barrier which reduces exchange between the polar caps and lower latitudes?More specifically, the research seeks to 1) characterize and quantify the transport circulation using both observed winds (from reanalysis products) and mean tracer motion in numerical simulations; 2) investigate and isolate the mechanisms of tropospheric transport in idealized models; 3) examine the causes of interannual variability in the transport circulation; and 4) investigate the changes in transport circulation associated with changes in time-mean (Eulerian) circulation induced by climate change (for example, the widening of the tropics and the poleward shift of the jet streams). The numerical simulations are performed using a hierarchy of models in which the most realistic is the Whole Atmosphere Community Climate Model (WACCM), which has a well-resolved stratosphere and sophisticated representations of atmospheric chemistry. Other models include an aquaplanet configuration of a global atmospheric model, used to study the transport circulation in an idealized setting which includes the effects of atmospheric moisture (including parameterized convection). Variations in the width of the Hadley cell, positions of the storm tracks and jet streams, and other circulation features would be created in the model by varying the imposed sea surface temperature, and the transport response to these variations would be examined. Further experiments would be performed using an idealized dry atmospheric model driven by highly simplified physics (primarily Newtonian damping), in which transport can be studied as a function of basic factors including atmospheric stability, equator-to-pole temperature gradient, and planetary rotation rate. Much of the diagnostic analysis of observations and model output focuses on the effective diffusivity of the longitudinally-averaged mean circulation. A new formalism based on equivalent latitude coordinates is used in which the longitudinally averaged meridional transport of tracers is represented as a resolved eddy flux and an effective downgradient diffusive flux.The education component of this CAREER proposal is based on demonstrations and experiments performed with a portable rotating tank. The tank is rotated to induce a Coriolis force and circulations can be generated in the tank which are analogous to the motions of Earth's atmosphere. The tank is used both on campus, in undergraduate and graduate courses, and in museum-based outreach to middle and high school student groups and to the general public. The on-campus activity consists of a week-long lab module incorporated into six different classes, in which students identify a phenomenon of interest (for example, a midlatitude cyclone) and design an experiment in the tank to simulate and study it. The rotating tank lab is motivated by a desire to present students with a hands-on learning experience which will allow students to develop an intuitive, hands-on appreciation for atmospheric dynamics. In the absence of such hands-on work students in atmospheric dynamics can become so focused on mastering the mathematical formalisms that they fail to appreciate the physical significance of the dynamical equations. The museum-based outreach would take place at teh Paleontological Research Institute's Museum of the Earth. Two forms of outreach are planned, one consisting of 50-minute demonstrations targeted to groups of middle and high school students, and another consisting of video presentations of atmospheric circulation features and their analogs in the rotating tank. The video exhibits would be complemented by 30-minute demonstrations of the rotating tank, to be performed on a monthly basis. The museum activities will be documented, evaluated by an external evaluator, and shared with other museums.In addition to the broader impacts of the education component, work under this award has societal relevance due to the effect of the transport circulation on atmospheric weather and pollution, as noted above. In addition, the work will have scientific broader impacts by building connections between the research communities engaged in atmospheric chemistry and atmospheric dynamics. The work will also support and train a graduate student, thereby providing for the future workforce in this research area.

这是一个职业奖项，其中的研究部分检查大气的运输循环。这里的输送环流是指气团和大气成分的运动，包括水蒸气和化学示踪剂，它们在被降雨或通过化学反应去除之前会长距离移动。大气的输送环流之所以引起人们的关注，有两个实际原因：首先，它在确定空气质量方面起着关键作用，因为当地的空气质量可能会受到远程污染源输送的污染物的影响。 其次，水蒸气、能量和动量的传输在很大程度上决定了天气模式的演变。 这不仅适用于日常天气，也适用于天气模式的逐月和逐年变化，例如与厄尔尼诺事件、急流波动和全球气候变化相关的天气模式。 在平流层中，输送环流决定了臭氧的分布以及臭氧空洞的大小和严重程度。 在这个项目中，主要关注的是南北方向的纵向平均运输环流，例如成分进出热带和极地帽的运动，以及这种运动被各种动力增强或阻碍的程度。流程。 例如，中纬度急流在多大程度上构成了混合屏障，减少了极冠和低纬度地区之间的交换？更具体地说，该研究旨在 1) 使用观测到的风（来自再分析产品）来表征和量化输送环流以及数值模拟中的平均示踪运动； 2）研究并分离理想化模型中对流层传输的机制； 3）研究运输环流年际变化的原因； 4) 研究与气候变化引起的时均（欧拉）环流变化相关的运输环流变化（例如，热带地区的扩大和急流向极地的移动）。 数值模拟是使用一系列模型进行的，其中最真实的是整个大气群落气候模型（WACCM），该模型具有良好解析的平流层和复杂的大气化学表示。其他模型包括全球大气模型的水行星配置，用于研究理想化环境中的输送环流，其中包括大气湿度（包括参数化对流）的影响。 通过改变施加的海面温度，将在模型中产生哈德利环流宽度的变化、风暴路径和急流的位置以及其他环流特征，并且将检查对这些变化的传输响应。 进一步的实验将使用由高度简化的物理学（主要是牛顿阻尼）驱动的理想化干燥大气模型进行，其中可以将传输作为基本因素的函数进行研究，包括大气稳定性、赤道到极点的温度梯度和行星自转速率。 观测和模型输出的大部分诊断分析都集中在纵向平均平均环流的有效扩散率上。 使用基于等效纬度坐标的新形式主义，其中示踪剂的纵向平均经向传输表示为解析的涡通量和有效的下降扩散通量。该职业提案的教育部分基于使用便携式计算机进行的演示和实验。旋转罐。旋转水箱以产生科里奥利力，并且可以在水箱中产生类似于地球大气运动的循环。 该水箱既可用于校园、本科生和研究生课程，也可用于博物馆向中学生群体和公众进行的宣传活动。 校园活动包括为期一周的实验室模块，分为六个不同的班级，学生在其中识别感兴趣的现象（例如中纬度气旋）并在水箱中设计一个实验来模拟和研究它。 旋转罐实验室的目的是为学生提供实践学习体验，使学生能够对大气动力学产生直观、动手的欣赏。 如果缺乏这样的实践工作，大气动力学专业的学生可能会过于专注于掌握数学形式，而无法理解动力学方程的物理意义。 博物馆的推广活动将在古生物学研究所的地球博物馆进行。 计划开展两种形式的宣传活动，一种是针对中学生群体的 50 分钟演示，另一种是通过视频演示大气环流特征及其在旋转罐中的类似情况。每月进行一次 30 分钟的旋转水箱演示，作为视频展览的补充。 博物馆的活动将被记录下来，由外部评估员进行评估，并与其他博物馆共享。除了教育部分的更广泛影响之外，由于交通运输对大气天气和污染的影响，该奖项下的工作还具有社会相关性，如上所述。 此外，这项工作将通过在从事大气化学和大气动力学的研究界之间建立联系来产生更广泛的科学影响。 这项工作还将支持和培训一名研究生，从而为该研究领域的未来劳动力提供支持。