CEDAR: Vertical Velocity Measurements in the Mesosphere: Biases and Possible Solutions Using Spatial Interferometry

由大气多普勒雷达得到的最重要的参数之一是中性风的垂直分量。该项目将比较和对比估计中间层垂直速度所用的各种方法。将使用中层-平流层-对流层(MST)和部分反射漂移(PRD)雷达来实现这一目标。MST雷达通常使用垂直指向波束或速度方位角显示(VAD)技术来估计垂直风。垂直波束技术可能会受到仪器和大气效应的影响。PIS建议，可以使用空间干涉测量(SI)来消除任何仪器偏差，以跟踪天鹅座A等射电恒星。天文位置与SI测量所得的天文位置之间的差异可归因于光束位置的系统偏移。由于反射率场不均匀而产生的任何大气偏差，也可以使用SI技术消除。如果实施得当，VAD技术可以产生对垂直风的无偏估计。另一方面，如果实施不当，得到的垂直速度估计将受到风场散度的影响。PIS计划在60-90公里范围内，在日本重崎使用中高层(MU)大气雷达，同时实施VAD和SI技术。这两种中间层测量基本上可以同时进行。由于典型系统的配置，大多数PRD测量仅限于垂直位置。因此，对于垂直指向的MST雷达，上述偏差同样适用于PRD系统。此外，由于这些雷达通常使用较宽的波束宽度，因此应该增强偏差。PRD雷达是工作在2-3 MHz的多接收器系统。因此，使用SI技术消除偏差的方法与MST的情况非常相似。PI将使用PRD雷达进行测量，克莱姆森大学和科罗拉多大学的研究人员计划在格陵兰岛的Sondre Stromfjord安装该雷达。

One of the most important parameters, which can be derived from atmospheric Doppler radars, is the vertical component of the neutral wind. This project will compare and contrast the various methods used in estimating the vertical velocity in the mesosphere. Mesosphere-stratosphere-troposphere (MST) and partial reflection drifts (PRD) radars will be used to achieve this goal. MST radars typically use either a vertically pointing beam or the velocity-azimuth-display (VAD) technique to estimate the vertical wind. The vertical beam technique can be biased by instrumental as well as atmospheric effects. The PIs propose that any instrumental bias can be removed using spatial interferometry (SI) to track a radio star such as Cygnus A. Differences between the astronomical position and that obtained from the SI measurements can be attributed to a systematic offset in the beam position. Any atmospheric bias, due to inhomogeneities in the reflectivity field, can also be removed using SI techniques. If implemented properly, the VAD technique can produce an unbiased estimate of the vertical wind. On the other hand, if not properly implemented, the resulting vertical velocity estimates will be biased by the divergence in the wind field. The PIs propose to implement both the VAD and SI techniques using the Middle and Upper (MU) Atmosphere radar in Shigaraki, Japan, in the 60-90 km range. Both these mesospheric measurements can be conducted essentially simultaneously. Most PRD measurements are restricted to the vertical position because of the configuration of typical systems. Therefore, the biases mentioned above, for the vertically pointing MST radar, are also applicable for PRD systems. Furthermore, the biases should be enhanced because of the typically wide beamwidths used with these radars. PRD radars are multiple-receiver systems operating at 2-3 MHz. As a result, the methods of eliminating the biases using SI techniques are very similar to the MST case. The PIs will make measurements using a PRD radar, which is planned for installation in Sondre Stromfjord, Greenland, by researchers at Clemson University and the University of Colorado.