Collaborative Research: Investigating the Characteristics of Lower Tropospheric Airborne GPS Radio Occultation Observations and Their Impact in Hurricane Studies

飓风的生成过程取决于支持深层对流所需的垂直不稳定程度和调节对流活动的中层增湿。然而，增湿的时间变化知之甚少，由于缺乏高的时间和空间观测过程中的成因。全球定位系统无线电掩星提供了具有非常高的垂直分辨率的区域平均地球活动剖面图（取决于湿度和温度），与下投式探空仪（逐点，高垂直分辨率）和卫星反演（高水平，但垂直分辨率差）相辅相成。GPS RO对强降水、云和风不敏感。 自气象、电离层和气候星座观测系统投入运行以来，星载全球定位系统反渗透数据已显示出对对流层中上部的全球数值天气预报模型的积极影响。 然而，由于以下几个原因，低层数据的使用已经滞后：1）由于湿度的强烈水平变化而引起的复杂性2）信号跟踪的困难和3）中尺度系统感兴趣的窗口内的稀疏观测。这使得热带气旋的形成和预报受到的影响最小，一般来说对流层中层以下的影响也最小。机载反渗透可以在促进对飓风成因过程的理解方面发挥重要作用，因为使用机载系统进行密集的有针对性的测量比使用现有的空间星座更简单。研究所将利用2010年8月热带云系低气压前调查活动期间的一个独特机会收集数据，这将使他们能够测试其在热带气旋成因数据同化方面的进展。 数据同化结果应该引起预测研究人员的极大兴趣，因为这些结果将为高分辨率模型提供更好的初始条件，以检验关于热带扰动演变成飓风的新假设。更广泛的影响：该项目将向扩大的研究界推广使用机载无线电掩星技术，并作为飓风猎人监测任务的可行性测试，有可能从改进的业务预报中直接产生社会效益。这项研究活动将教育研究生，并促进台湾和美国大学之间的国际合作结构中的博士后研究人员的进步。它将加强由四名女性研究人员领导的研究项目，她们将成为学生和其他年轻女科学家的榜样。

The hurricane genesis process is known to depend on the degree of vertical instability needed to support deep convection and on mid-level moistening, which modulates convective activity. However, the time variation of moistening is poorly known due to the lack of high temporal and spatial observations during the genesis process. Global Positioning System (GPS) Radio Occultation (RO) provides area-averaged profiles of refractivity (which depends on moisture and temperature) with very high vertical resolutions that are complementary to dropsondes (pointwise, high vertical resolution) and satellite retrievals (high horizontal but poor vertical resolution). GPS RO is insensitive to heavy precipitation, clouds, and winds. Since the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) became operational, space borne GPS RO data have shown a positive impact on global numerical weather prediction models in the mid to upper troposphere range. However, the use of the data at lower levels has lagged for several reasons: 1) complications due to strong horizontal variations in moisture 2) difficulties in signal tracking and 3) sparse observations within the window of interest for mesoscale systems. This has led to minimal impact in tropical cyclone genesis and forecasting, and minimal impact below mid-troposphere in general. Airborne RO can play a major role in advancing understanding of the hurricane genesis process, because dense targeted measurements are simpler to make with an airborne system than with the existing space borne constellation. The PIs will take advantage of a unique opportunity to collect data during the Pre-Depression Investigation of Cloud Systems of the Tropics (PREDICT) campaign in August 2010, which will allow them to test their progress in data assimilation for the case of tropical cyclone genesis. The data assimilation results should be of great interest to PREDICT investigators because they will provide better initial conditions for high-resolution models for testing new hypotheses concerning the evolution of tropical disturbances into hurricanes. Broader Impacts: The project will promote the use of airborne radio occultation to an expanded research community and serve as a feasibility test for hurricane hunter surveillance missions, potentially resulting in a direct societal benefit from improved operational forecasts. This research activity will educate graduate students and promote the advancement of postdoctoral researchers within an international collaborative structure between Taiwan and US universities. It will strengthen research programs led by four female investigators, who will serve as role models for their students as well as other young female scientists.