Finite-amplitude Eddy-mean Flow Interaction in the Extratropical Atmosphere

温带大气中的有限振幅涡均流相互作用

• 批准号: 1151790
• 负责人: Noboru Nakamura
• 金额: $ 56.78万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-02-01 至 2016-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1151790&HistoricalAwards=false
• 关键词: Finite; amplitude; Eddy; mean; Flow; Finite; amplitude; Eddy; mean; Flow

The mutual interaction between eddies (such as those associated with midlatitude weather systems) and the mean flow (midlatitude jet streams, in particular) is a longstanding topic in atmospheric general circulation. It is clear that jet streams and eddies interact strongly, but traditional theories to account for their interaction are limited because, for mathematical reasons, they assume that the eddies are small-amplitude perturbations of the mean flow. The Principal Investigator (PI) has developed a theory of eddy-mean flow interaction which works for large-amplitude eddies, and work conducted under the award seeks to explore the implications of this new theory. The new theory will be applied to 1) evaluate nonconservative driving of the climate state (radiative forcing, friction, mixing, etc.) by carefully documenting and analyzing the slowly varying reference state; 2) quantify the stabilizing effects of baroclinic eddies ("baroclinic adjustment") by comparing the linear stability of the observed zonal-mean time-mean state and that of an eddy-free reference state derived from the theory; 3) characterize annular mode variability as co-variation of the zonal-mean zonal-wind and wave activity density, and in turn associate it with the variation in the zonal phase speed and energy of the eddies; 4) generalize the criterion for the onset of Rossby wave breaking and testing this theoretical prediction with numerical simulation and meteorological reanalysis; and 5) further generalize the wave breaking criterion for zonally varying mean flows.The broader impacts of this activity are that the eddy-mean flow theory and the diagonstic tools derived from it can be applied to a wide class of flows, including the stratosphere, troposphere, and the oceans. In addition, the project will support and train two graduate students, thereby developing the scientific workforce in this area. Results of the research will also be incorporated into demonstrations performed by the PI in his fluid dynamics laboratory, for audiences at the graduate, undergraduate, and high school levels.

涡流（例如与中纬度天气系统相关的涡流）与平均流动（尤其是中纬度喷射流有关的涡流）之间的相互作用是大气一般循环中的一个长期话题。 显然，喷气流和涡流相互作用很强，但是解释其相互作用的传统理论是有限的，因为出于数学原因，他们认为涡流是平均流量的小振幅扰动。 首席研究员（PI）开发了一种涡流流相互作用的理论，该理论适用于大振幅涡流，并根据该奖项进行的工作旨在探索这种新理论的含义。 新理论将应用于1）评估气候状态的非保守驾驶（辐射强迫，摩擦，混合等），通过仔细记录和分析缓慢变化的参考状态； 2）通过比较观察到的层次均值时态态的线性稳定性和源自该理论的无涡流参考状态的线性稳定性，量化斜压涡流（“斜压调节”）的稳定作用； 3）将环形模式变异性表征为Zonal均值Zonal-Wind和波浪活性密度的共同变化，然后将其与涡流相位速度和涡流的零相速度和能量的变化相关联； 4）概括了通过数值模拟和气象重新分析的理论预测的Rossby Wave Breaking和测试的标准； 5）进一步概括了碎区变化平均流的波浪破坏标准。该活动的更广泛的影响是，涡流流程理论和从其的对角线工具可以应用于一类宽类的流，包括平流层，对流层和海洋。 此外，该项目将支持和培训两名研究生，从而在该领域发展科学劳动力。 这项研究的结果还将被纳入PI在其流体动力学实验室中进行的示范，毕业生，本科和高中级别的观众。