Study of the Spatial and Temporal Distribution of Atmospheric Gravity Waves Using Pressure Data From the Dense USArray Transportable Array

美国国家科学基金会为一个前所未有的观测站提供了资金，用于研究地球内部和大气层。 USArray便携式阵列是一个400站的观测站，它将宽带地震和大气压力传感器放置在笛卡尔网格上，每隔70公里，跨越200万平方公里的区域。 这些台站的地震数据提供了美国大陆下方地球内部的高分辨率图像，而这些台站的大气数据则提供了大气现象的测量数据。 在最近由NSF资助的一个项目中，UCSD的研究人员开发了一种检测波长很长的压力扰动的方法，并描述了它们如何穿过TA。与大气研究人员的讨论证实，在地球表面探测到的这些压力扰动与卫星测量在30-50公里高度探测到的重力波相吻合，在这项研究中，研究人员正在进一步将卫星观测到的重力波与地面记录的压力扰动进行直接比较，目的是确定这些现象发生的时间和地点。由于重力波在将能量从地球表面附近转移到高层大气中起着很大的作用，因此这项研究有助于了解全球大气环流。美国国家科学基金会的EarthScope/USAray便携式阵列（TA）的升级，包括空气压力传感器在每个站开辟了新的途径，研究大气现象和大气与固体地球的相互作用。该网络将高质量的压力传感器放置在一个规则的、密集的笛卡尔网格上，覆盖面积约为2，000，000平方公里，这种配置允许对广泛的大气波现象进行定量分析。 UCSD小组正在使用新的压力数据来研究TA跨越的中纬度地区的大气重力波。UCSD小组开发了一种技术，用于检测波长大于100 km的重力波，并表征其在TA中的传播，从而定量测量其特征（速度，方向，周期和振幅）如何随TA整个足迹的位置而变化。 该方法将来自TA的大量数据减少为可用于进一步研究的定量记录。该研究包括与Lars Hoffmann博士（Juelich超级计算中心）合作，将使用卫星辐射数据检测到的重力波与使用UCSD应用于TA压力数据的技术检测到的重力波进行比较。卫星和地面压力传感器为研究大气重力波提供了根本不同的平台。 虽然这些数据集和应用于它们的分析方法完全不同，但对结果的初步比较表明两者之间存在一致性。这项工作有两个主要目标。首先，正在详细研究大对流事件的TA记录，并将其与相同事件的卫星记录进行比较。目的是确定在地面压力传感器检测到的重力波是否与平流层重力波在时间和位置上一致，以及在TA足迹内检测到的重力波是否主要是对流或造山起源。 UCSD小组正在研究和记录探测到的重力波的其他特征，特别是它们的速度，幅度和方向。 第二，正在对重力波发生情况进行统计研究，目的是确定重力波发生率的日、季和区域趋势。这项工作的一个关键成果是在为期4年的研究期间对重力波进行统计。 拟议的研究既有助于大气科学，也有助于更好地了解重力波对次声传播的影响。

Non-technical statementThe National Science Foundation has provided funds for an unprecedented observatory for study of the Earth's interior and the atmosphere. The USArray Transportable Array is a 400-station observatory that places broadband seismic and atmospheric pressure sensors on a Cartesian grid every 70 km across an area that spans 2,000,000 square km. Seismic data from these stations have provided high-resolution images of the Earth's interior beneath the continental United States, whereas the atmospheric data at these stations provide measurements of atmospheric phenomena. In a project recently funded by NSF, researchers at UCSD developed a method to detect very long wavelength pressure disturbances, and described how they traveled across the TA. Discussions with atmospheric researchers confirmed that these pressure disturbances detected on the Earth's surface coincided with gravity waves detected by satellite measurements, at 30-50 km altitude.In this research, the researchers are making further direct comparisons of satellite observations of gravity waves with pressure disturbances recorded at ground level, with the goal of determining when and where these phenomena occur. Since gravity waves play a large part in transferring energy from near the Earth's surface to the upper atmosphere, this research is contributing to the understanding of global atmospheric circulation. Technical AbstractThe upgrade of NSF's EarthScope/USArray Transportable Array (TA) to include air pressure sensors at each station has opened up new avenues for research into atmospheric phenomena and the interaction of the atmosphere and solid Earth. This network places high quality pressure sensors on a regular, dense Cartesian grid across an area of about 2,000,000 square km, a configuration that allows for quantitative analyses of a broad range of atmospheric wave phenomena. The UCSD group is using the new pressure data to study atmospheric gravity waves at the mid-latitudes spanned by the TA. The UCSD group has developed a technique to detect gravity waves with wavelengths greater than 100 km and characterize their propagation across the TA, yielding a quantitative measure of how their characteristics (speed, direction, period, and amplitude) may change with location across the full footprint of the TA. The method reduces the large volume of data from the TA into a quantitative record that can be used for further study.The research includes a collaboration with Dr Lars Hoffmann (Juelich Supercomputing Centre) to compare gravity waves detected using satellite radiance data with those detected using UCSD's technique applied to TA pressure data. Satellites and ground-based pressure sensors provide fundamentally different platforms for studies of atmospheric gravity waves. Although these datasets and the analytical methods applied to them are completely different, a preliminary comparison of the results suggests agreement between the two. There are two main objectives of this effort. First, TA recordings of large convective events are being studied in detail and compared with satellite recordings of the same events. The objective is to determine whether gravity waves detected at ground-sited pressure sensors are coincident in time and location with stratospheric gravity waves, and whether gravity waves detected within the footprint of the TA are dominantly convective or orogenic in origin. The UCSD group is studying and documenting other characteristics of the detected gravity waves; specifically their speed, amplitude and direction. Second, a statistical study of the occurrence of gravity waves is being conducted with the objective of determining the diurnal, seasonal and regional trends in the occurrence rates of gravity waves. A key deliverable of this effort is the statistics of gravity waves during the 4-year study. The proposed research is contributing both to atmospheric science and to improved understanding of the effects of gravity waves on infrasound propagation.