Wave Characteristics from the COSMIC and CHAMP Global Positioning System (GPS) Temperature Profiles

重力波在地球大气层中无处不在。它们在动量和化学成分的垂直输送中发挥着重要作用，所有全球气候模型现在都包括了重力波效应的参数化项。然而，由于重力波的时间和空间尺度太短，无法通过传统的气象观测网络进行解析，因此这些参数化受到观测值的约束很差。主要研究人员将利用全球定位系统(GPS)信号的无线电掩星获得的新获得的高垂直分辨率温度剖面，得出有关重力波活动和动量传输的全球信息。这些数据是由低地球轨道上的两个卫星星座CHAMP(挑战小卫星有效载荷)和COSMIC(星座气象、电离层和气候观测系统)获取的，这两个星座每天提供几乎均匀分布在全球各地的数千个温度廓线。利用这些全球数据，PI将通过去除那些投射到大水平空间尺度上的变化来提取重力波对温度结构的贡献。重力波的水平波数和传播方向将根据相邻温度廓线之间的位相差确定，并将估计由于波活动而产生的水平动量垂直通量-这是全球模式中重力波参数化必须计算的量。GPS数据的数量和全球覆盖将使PI能够将重力波活动与不同的源联系起来，包括地形、对流、风切变、天气锋面和地转调整。将使用射线跟踪方法探索观测到的波与可能的源之间的联系。全球数据还将允许以前所未有的精度确定大尺度大气波的结构和可变性，例如赤道开尔文波。随着数据的积累，将有可能探索重力波活动的时间变异性及其与大气行星尺度环流变化的关系，例如准两年一次的振荡和平流层突然变暖。这项研究的更广泛的影响在于，更好的重力波信息对于全球气候模式的重力波参数化开发者和研究波与高纬度卷云的相互作用具有重要意义。

Gravity waves are ubiquitous in Earth's atmosphere. They play important roles in the vertical transport of momentum and chemical constituents, and all global climate models now include a parameterization of gravity-wave effects. These parameterizations are, however, poorly constrained by observations, since gravity waves have time and space scales too short to be resolved by the conventional meteorological observing network. The principal investigators (PIs) will derive global information about gravity wave activity and momentum transport using newly available, high vertical resolution, temperature profiles obtained from the radio occultation of global positioning system (GPS) signals. These data are acquired by two constellations of satellites in low Earth orbit, CHAMP (Challenging Minisatellite Payload) and COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate), which provide thousands of temperature profiles each day, distributed nearly uniformly over the globe.Using these global data, the PIs will extract the gravity-wave contribution to the temperature structure by removing those variations that project onto large horizontal spatial scales. The horizontal wavenumbers and propagation directions of gravity waves will be determined from the phase differences between adjacent temperature profiles, and the vertical flux of horizontal momentum due to the wave activity will be estimated - this is the quantity that must be calculated by gravity-wave parameterizations in global models.The quantity and global coverage of the GPS data will allow the PIs to associate gravity-wave activity with different sources, which include topography, convection, wind shear, synoptic fronts, and geostrophic adjustment. The connections of observed waves to likely sources will be explored using ray-tracing methods. The global data will also permit the structures and variability of large-scale atmospheric waves, such as equatorial Kelvin waves, to be determined with unprecedented accuracy. As data accumulate over time, it will be possible to explore the temporal variability of gravity-wave activity and its associations with variations in the planetary scale circulation of the atmosphere, such as the quasi-biennial oscillation and sudden stratospheric warmings.Broader impacts of this research are in the importance of better gravity-wave information to the developers of gravity-wave parameterizations for global climate models and for research on wave interactions with high-latitude cirrus clouds.