CAREER: Understanding the Transport Circulation of the Troposphere

这是一个职业奖项，其中研究部分研究大气的输送环流。这里的输送环流指的是气团和大气成分的运动，包括水蒸气和化学示踪剂，它们在被降雨或被化学反应带走之前，经过很长的距离移动。大气的输送环流之所以令人感兴趣，有两个实际原因：第一，它在决定空气质量方面发挥着关键作用，因为当地的空气质量可能会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，也适用于与厄尔尼诺事件、急流波动和全球气候变化有关的天气模式的月际和年际变化。在平流层，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，主要的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，以及这种运动被各种动力过程加强或阻碍的程度。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，这项研究试图1)在数值模拟中利用观测到的风(来自再分析产品)和平均示踪运动来表征和量化输送环流；2)在理想化模式中研究和隔离对流层输送的机制；3)检验输送环流年际变化的原因；4)研究气候变化(例如，热带加宽和急流极移)引起的时间平均(欧拉)环流变化引起的输送环流的变化。数值模拟是使用一系列模式进行的，其中最真实的是全大气社区气候模式(WACCM)，该模式具有良好的平流层分辨率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结构，用于研究包括大气湿度(包括参数对流)影响的理想环境中的输送循环。哈德利环流宽度、风暴路径和急流的位置以及其他环流特征的变化将通过改变施加的海面温度在模式中产生，并将检查对这些变化的输送响应。进一步的实验将使用由高度简化的物理(主要是牛顿阻尼)驱动的理想化干大气模型，在该模型中，传输可以作为基本因素的函数来研究，包括大气稳定性、赤道到极地的温度梯度和行星自转速度。对观测和模式输出的大部分诊断分析集中在纵向平均平均环流的有效扩散率上。使用了一种新的基于等效纬度坐标的形式，其中示踪剂的经向平均输运被表示为一个可分辨的涡流通量和一个有效的下坡扩散通量。这项职业计划的教育部分是基于在便携式旋转水箱上进行的演示和实验。水箱旋转以产生科里奥利力，在水箱中可以产生类似于地球大气运动的循环。这种坦克在校园、本科生和研究生课程中都有使用，也在博物馆的初高中学生团体和普通公众中使用。校园活动包括一个为期一周的实验模块，分成六个不同的班级，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。旋转水箱实验室的动机是希望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的、动手的欣赏。如果没有这样的实践工作，大气动力学专业的学生可能会过于专注于掌握数学形式，以至于他们无法认识到动力学方程的物理意义。以博物馆为基础的外展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推广活动，一种是针对初中生群体的50分钟演示，另一种是对旋转水箱中的大气环流特征及其类似物进行视频演示。视频展品将辅之以30分钟的旋转水箱演示，每月进行一次。博物馆的活动将被记录下来，由外部评估者进行评估，并与其他博物馆分享。如上所述，除了教育部分的更广泛影响外，该奖项下的工作还具有社会意义，因为交通循环对大气天气和污染的影响。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，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。

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.