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，其中的研究部分检查大气的运输循环。这里的输送环流指的是空气质量和大气成分的运动，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长距离移动。大气层的输送环流之所以令人感兴趣，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受到从遥远来源输送的污染物的影响。 其次，水汽、能量和动量的输送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月与月和年与年的变化，例如与厄尔尼诺事件，急流波动和全球气候变化有关的变化。 在平流层中，输送环流决定了臭氧的分布以及臭氧洞的大小和严重程度。 在这个项目中，主要重点是南北方向的纵向平均输送环流，例如成分进出热带和极冠的运动，以及各种动力过程增强或阻碍这种运动的程度。 例如，中纬度急流在多大程度上构成了减少极冠和低纬度之间交换的混合障碍？更具体地说，这项研究旨在1）利用观测到的风和（2）研究和分离理想模式中对流层输送的机制：（3）研究输送环流年际变化的原因;（4）研究与气候变化（例如热带的扩大和急流的极向移动）引起的时间平均（欧拉）环流变化有关的输送环流的变化。 数值模拟是使用一系列模型进行的，其中最现实的是全大气社区气候模型（WACCM），该模型具有良好的平流层分辨率和大气化学的复杂表示。其他模型包括全球大气模型的水行星配置，用于研究理想环境中的输送环流，其中包括大气水分的影响（包括参数化对流）。 通过改变强加的海面温度，将在模式中产生哈德利环流圈宽度、风暴路径和急流位置以及其他环流特征的变化，并将研究对这些变化的输送反应。 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，其中可以研究运输作为基本因素的函数，包括大气稳定性，赤道到极点的温度梯度和行星旋转速率。 观测和模式输出的诊断分析主要集中在平均环流的有效扩散率上。 一个新的形式主义的基础上等效纬度坐标的纵向平均纬向运输示踪剂被表示为一个解决的涡流通量和一个有效的downgradient扩散flux.The教育部分的职业生涯建议是基于演示和实验进行便携式旋转罐。旋转罐以引起科里奥利力，并且可以在罐中产生类似于地球大气的运动的环流。 该坦克既用于校园，在本科和研究生课程，并在博物馆为基础的推广到初中和高中学生团体和公众。 校内活动包括一个为期一周的实验室模块，该模块被纳入六个不同的课堂，学生在其中识别感兴趣的现象（例如，中纬度气旋），并在水槽中设计一个实验来模拟和研究它。旋转水槽实验室的动机是希望为学生提供一个动手学习的经验，这将使学生能够开发一个直观的，对大气动力学的亲身体验 在没有这种动手工作的情况下，大气动力学的学生可能会过于专注于掌握数学形式主义，以至于他们无法理解动力学方程的物理意义。 以博物馆为基础的外联活动将在古生物研究所的地球博物馆进行。 计划开展两种形式的宣传活动，一种是针对初中和高中学生群体的50分钟演示，另一种是关于大气环流特征及其在旋转罐中的类似物的视频演示。除了录像展览外，还将每月进行30分钟的旋转罐演示。 博物馆的活动将被记录下来，由外部评估员进行评估，并与其他博物馆分享。除了教育部分的广泛影响外，该奖项下的工作还具有社会意义，因为运输流通对大气天气和污染的影响，如上所述。 此外，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，这项工作将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，从而为这一研究领域的未来劳动力提供支持。