RAPID: The GNSS Instrument System for Multistatic and Occultation Sensing (GISMOS) for Future Application to Precipitation Processes in Atmospheric River Events

大气中的河流为北极、太平洋西北部和加利福尼亚海岸线带来了大量的水分，导致了强降水。目前还不完全了解水汽和气溶胶的垂直分布如何影响降水过程，特别是在降水效率和到达北纬并可与冷锋相互作用的水汽通量方面。如果能够利用水汽和降水垂直分布的直接信息来研究这类事件期间模式对物理参数化的敏感性，将是有利的。虽然模型调整方法对于当前气候总体上是成功的，但随着气候的变化，并不一定期望同样的方法也会成功。因此，在这些高水汽通量区域同时测量大尺度水成物和水汽的垂直分布，为降水预测提供更可靠的依据至关重要。利用GPS无线电掩星的机载湿度测量可以作为一种有针对性的观测方法，与其他机载和卫星观测相结合，为解决这一科学问题提供数据。最近的模拟表明，通过测量左手圆极化（LHCP） GPS信号的前向散射效应，可以探测到大雨滴的存在。如果可以证明这是可行的，那么机载GPS无线电掩星测量不仅可以从正常的RHCP信号中提供折射率曲线，还可以从差分LHCP减去RHCP信号中提供强降水存在和降水率的指示。作为朝这个方向迈出的第一步，将使用现有的GISMOS仪器在强降水事件期间进行一些初步测量。2014年10月至11月，NASA DC-8将从加利福尼亚飞往智利，然后穿越德雷克海峡，这将提供这样一个机会，在热带辐合带上空可能有强降水的样带上测试使用备用天线配置的数据收集。2014年8月期间的飞行试验还将提供一种手段，对GISMOS仪器进行一些必要的维护，使其为今后专门从事大气河流事件任务的工作做好准备，并供更大的国家科学基金会使用。知识价值：将GISMOS与高垂直分辨率的湿度传感同时用于降水传感，这一原创和创新的尝试将促进降水过程的有效建模。该项目将重点研究大气河流的物理现象，这是热带地区向中纬度地区输送水分的重要过程。更广泛的影响：作为HIAPER仪器套件的一部分，GISMOS仪器的翻新和准备工作将继续由NSF社区使用，通过对低层大气观测设施做出贡献，增强研究基础设施。这些修改使得GISMOS的GPS/INS组件与GPS遥感组件分开使用成为可能，并且通过大大提高现有仪器的精度，直接使使用GV飞机的任何研究人员受益。

Atmospheric rivers are responsible for bringing large quantities of moisture to the arctic, Pacific Northwest, and California coastlines, leading to heavy precipitation. It is not fully understood how the vertical distribution of moisture and aerosols affects precipitation processes, especially in terms of precipitation efficiency and the flux of moisture that reaches northern latitudes and is available for interaction with cold fronts. It would be advantageous to be able to use direct information on the vertical distribution of moisture and precipitation to investigate the sensitivity of the models to the physics parameterizations during this type of event. While the model tuning approach has in general been successful for the current climate, it is not necessarily expected that as climate changes, the same will be true. Therefore, to make simultaneous measurements of the large-scale vertical distribution of hydrometeors and moisture in these regions of high moisture flux to have a more reliable basis for predicting precipitation is crucial. Airborne measurements of moisture using GPS radio occultation can be used as a targeted method of observation to provide data to address this scientific question, in concert with other airborne and satellite observations.Recent simulations indicate the possibility of detecting the presence of large raindrops from forward scattering effects measured on left-hand circularly polarized (LHCP) GPS signals. If this can be shown to be feasible, then airborne GPS radio occultation measurements could not only provide refractivity profiles from normal RHCP signals, but also provide indications of the presence of heavy precipitation and precipitation rates from differential LHCP minus RHCP signals. As a first step in this direction, some preliminary measurements during heavy precipitation events will be made using the existing GISMOS instrument. A NASA DC-8 flight operation in October-November 2014 on flights from California to Chile, then transects across the Drake Passage will provide such an opportunity, which would test data collection with alternate antenna configurations, on the transect over the inter tropical convergence zone where heavy precipitation is likely. Flight tests during August 2014 would also provide a means for performing some needed maintenance on the GISMOS instrument, to prepare it for future work on missions dedicated to atmospheric river events, and for use by the larger NSF community.Intellectual Merit:The attempt to develop this original and innovative use of GISMOS for precipitation sensing simultaneously with moisture sensing with high vertical resolution will advance effective modeling of precipitation processes. The project will focus on the physical phenomenon of atmospheric rivers, an important process of moisture transport from the tropics to mid-latitudes.Broader Impacts:The refurbishing and preparation of the GISMOS instrumentation for continued use by the NSF community as part of the HIAPER suite of instrumentation enhances infrastructure for research by contributing to the Lower Atmospheric Observing Facility. The modifications make it possible to use the GPS/INS component of GISMOS separately from the GPS remote sensing components, and directly benefit any researcher using the GV aircraft by substantially increasing the accuracy over the existing instrumentation.