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

引力波在地球大气中无处不在。它们在动量和化学成分的垂直输送中起着重要作用，现在所有的全球气候模式都包括重力波效应的参数化。然而，由于引力波的时间和空间尺度太短，传统的气象观测网无法分辨，这些参数化受到观测的约束很差。主要研究人员（pi）将利用全球定位系统（GPS）信号的无线电掩星获得的最新可用的高垂直分辨率温度剖面，获得有关重力波活动和动量输运的全球信息。这些数据是由低地球轨道上的两个卫星星座获得的，CHAMP（挑战小卫星有效载荷）和COSMIC（气象、电离层和气候星座观测系统），它们每天提供数千个温度剖面，几乎均匀地分布在全球各地。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由相邻温度剖面之间的相位差确定，并将估计由波活动引起的水平动量的垂直通量——这是全球模式中必须通过重力波参数化计算的量。GPS数据的数量和全球覆盖范围将允许pi将重力波活动与不同的来源联系起来，这些来源包括地形、对流、风切变、天气锋和地转调整。观测到的波与可能的源之间的联系将使用射线追踪方法进行探索。全球数据也将允许以前所未有的精度确定大尺度大气波（如赤道开尔文波）的结构和变化。随着时间的积累，将有可能探索重力波活动的时间变异性及其与行星尺度大气环流变化的关系，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，对于全球气候模式的重力波参数化的开发人员和高纬度卷云波浪相互作用的研究人员来说，更好的重力波信息具有重要意义。

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.