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

大气河流给北极、太平洋西北部和加利福尼亚州的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分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。能够使用关于水分和降水的垂直分布的直接信息来调查模式对这类事件期间的物理参数的敏感性将是有利的。虽然模型调整方法在当前气候下总体上是成功的，但不一定期望随着气候变化，同样的方法也会成功。因此，在这些高水汽通量地区同时测量水流星和水汽的大尺度垂直分布，为降水预报提供更可靠的依据是至关重要的。利用GPS无线电掩星的航空湿度测量可以作为一种有针对性的观测方法，与其他航空和卫星观测相结合，为解决这一科学问题提供数据。最近的模拟表明，通过在左手圆偏振(LHCP)GPS信号上测量的前向散射效应，可以检测到大雨滴的存在。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信号提供折射率分布，还可以从不同的LHCP减去RHCP信号提供强降水的存在和降雨率的指示。作为这一方向的第一步，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。美国国家航空航天局将于2014年10月至11月进行DC-8飞行，从加利福尼亚州飞往智利，然后横跨德雷克航道，这将提供这样一个机会，即在热带辐合带上空可能出现强降水的横断面上测试使用替代天线配置的数据收集。2014年8月的飞行测试还将提供一种手段，对GISMOS仪器进行一些必要的维护，为今后专门研究大气河流事件的飞行任务做好准备，并供更大的国家科学基金会使用。智力上的好处：试图开发这种将GISMOS用于降水传感的原创和创新用途，同时进行高垂直分辨率的湿度传感，将促进对降水过程的有效建模。该项目将侧重于大气河流的物理现象，这是水汽从热带输送到中纬度的一个重要过程。广泛的影响：翻新和准备GISMOS仪器，供NSF社区继续使用，作为HIAPER仪器套件的一部分，通过为低大气观测基金作出贡献，加强研究基础设施。这些改进使GISMOS的GPS/INS组件与GPS遥感组件分开使用成为可能，并通过大幅提高现有仪器的精度，使使用GV飞机的任何研究人员直接受益。

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.