CEDAR: Impacts of Lower Atmosphere Forcing on the Mesosphere-lower Thermosphere and Ionosphere During September Equinox Transition

该奖项支持基于卫星数据分析的调查，其中等离子体密度、氧成分和中间层低层热层温度是选定的关键参数。本研究的目的是了解在9月春分期间观察到的电离层总电子含量（TEC）的短期变化如何可以解释为低层和高层大气区域之间的波耦合的结果。这些TEC变化可以被描述为电离层天气，这种天气是由于几个耗散过程而发生的，这些耗散过程是由100至350公里区域的大尺度低层大气波与电离层等离子体耦合所支持的。本奖项将研究的关键思想是基于这样一个事实，即从低层大气区域向上传输的大尺度波在分点期间达到最大值。正常情况下，平流层的风会阻止这些波到达如此高的高度。然而，9月春分是平流层风的方向在冬季转向东方，在夏季转向西方的时候。在春分期间，这些平流层风较弱，然后通过大气中部区域传播大尺度波成为可能。这项调查将比较9月分点研究计算的100至350公里范围内的氧组成、温度和等离子体密度的模拟结果与同期卫星测量的这些数量。本科生将通过大气研究与科学（SOARS）计划的重大机会参与拟议的研究活动。一位SOARS学生的参与将有助于加强历史上代表性不足的群体对大气科学的参与。这项研究将通过提高对电离层短期、日常变化的理解，进一步造福社会。由于电离层对通信和导航信号的影响，了解这种可变性至关重要。建模研究将使用新开发的最先进的全大气数据同化模型（WACCMX）对等离子体密度进行数值模拟。在WACCMX中纳入数据同化将代表第一个具有全面电离层和热层的全大气模式，包括数据同化能力，使人们能够在特定事件期间对低层大气耦合有新的认识。采用资料同化全大气模式，可以直接将数值模拟结果与观测结果进行比较。这种能力将用于诊断导致观察到的可变性的机制。提案目标的实现将导致对高层大气变异性的全面了解，这种变异性是利用9月春分转变作为高层大气动力学总体范围内的代表性简化案例研究而发生的。这种简化是平流层风在反转期间减弱的结果。因此，消除了详细了解平流层风的需要，提高了评估和测量模拟高层大气动力学中正在进行的其他物理过程的建模能力的能力。

This award supports the investigation based upon the analysis of satellite data with plasma density, oxygen composition, and mesosphere lower thermosphere temperatures being the key parameters selected. The goal of this investigation is to understand how the short-term variability that is observed in the ionosphere total electron content (TEC) during the September equinox may be explained as a result of the wave coupling between the lower and upper atmosphere regions. These TEC variations can be characterized as ionospheric weather that occur as a result of several dissipative processes that are supported by the coupling of large scale lower atmosphere waves to the ionospheric plasma of the region between 100 to 350 km. The key idea that would be studied in this award is based upon the fact that the transmission of large scale waves upward from the lower atmosphere region maximizes during the equinoctial period. Normally, the stratospheric winds would block these waves from reaching such high heights. However, the September equinox is when the direction of stratospheric winds reverses direction being eastward during winter and westward during the summer. During the equinox, these stratospheric winds are weak and then transmission of the large scale waves through the middle atmosphere region becomes possible. The investigation will compare modeled results for the oxygen composition, temperature, and plasma densities in the region of 100 to 350 km computed for the September equinoctial study to the satellite measurements of these quantities for this same period. An undergraduate student will be involved in the proposed research activities through the Significant Opportunities in Atmospheric Research and Science (SOARS) program. The involvement of a SOARS student will serve to enhance participation of historically under-represented groups in the atmospheric sciences. The research will further benefit society through an improved understanding of short-term, day-to-day, variability in the ionosphere. Understanding this variability is critical due to the impact of the ionosphere on communication and navigation signals. The modeling research would use numerical simulations of the plasma densities using a newly-developed, state-of-the-art whole atmosphere data assimilation model (WACCMX). Incorporation of data assimilation in WACCMX will represent the first whole atmosphere model with a comprehensive ionosphere and thermosphere to include the data assimilation capability, enabling new insights into lower-upper atmosphere coupling during specific events. By employing a data assimilation whole atmosphere model, the numerical simulations can be directly compared with the observations. This capability will be used to diagnose the mechanisms responsible for the observed variability. The realization of the proposal objectives will result in an overall improved understanding of the upper atmosphere variability that occurs using the September equinox transition as a representative simplified case study drawn from the overall range of upper atmosphere dynamics. This simplification is a result of the weakness of stratospheric winds during the reversal period. The elimination of the need to know in detail the stratospheric winds thus enhances the ability to assess and measure the modeling capability to simulate the other physical processes ongoing in upper atmosphere dynamics.