EAGER: Exploratory Measurements of Large Winds and Shears in the Lower Thermosphere and Their Variability Using an Enhanced Sodium Lidar

在海拔120 km附近的高层大气是一个重要的过渡区域，主要的混合过程由小漩涡或小涡流的相互作用（旋涡扩散）转变为单个分子的相互作用（分子扩散）。这也是高层大气中众所周知的难以观测的部分，因为传统的地面技术，如激光雷达，由于信号功率低，通常无法测量100公里以上的高度，而且卫星轨道高度较高，以减少大气阻力。偶尔的火箭测量显示，该地区出现了意想不到的巨大垂直和水平中性风和切变。这些风被认为对形成强而薄的金属离子层以及形成控制连接不同大气层的大气波的消散和垂直传播的临界层至关重要。该项目将使用由犹他州立大学（USU）运营的最先进的钠激光雷达系统，首次提供大型水平和垂直风的综合测量。该项目将通过USU激光雷达观测站参与犹他州卡什谷农村社区的公共宣传活动来提高公众素养。该项目还将为USU的一名研究生和一名本科生提供培训。该项目将包括(1)更换干扰滤光片，这将通过减少2倍的相关不确定性来提高风测量的质量，(2)使用配备大孔径（~5 m^2接收面积）的增强型USU钠激光雷达进行探索性测量，以及(3)分析100至120公里高度的低热层区域强风和切变的时间变化和持续时间。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The upper atmosphere near 120 km in altitude is an important transitional region where the dominant mixing processes change from interaction of small swirls or eddies (eddy diffusion) to interaction of individual molecules (molecular diffusion). This is also the part of the upper atmosphere that is notoriously difficult to observe since traditional ground-based techniques such as lidar generally cannot measure above 100 km due to low signal power and since satellites orbit at higher altitudes to reduce atmospheric drag. Occasional rocket measurements revealed unexpected large vertical and horizontal neutral wind and shears in this region. These winds are believed to be critically important in formation of intense and thin layers of metallic ions as well as in formation of critical layers that control dissipation and vertical propagation of atmospheric waves connecting different atmospheric layers. This project will provide first comprehensive measurements of large horizontal and vertical wind by using a state-of-the-art sodium lidar system operated by the Utah State University (USU). The project will improve public literacy by the USU lidar observatory participating in public outreach events in the Utah Cache Valley rural community. This project will also provide training for one graduate student and one undergraduate student at USU. The project will involve (1) replacement of interference filters which will improve the quality of the wind measurement by reducing the associated uncertainties by a factor of 2, (2) exploratory measurements with the enhanced USU sodium lidar equipped with large aperture (~5 m^2 receiving area), and (3) analysis of temporal variations and duration of strong winds and shears in the lower thermospheric region between 100 and 120 km in altitude.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.