The Cloud Microphysical Effects of Ground-based Glaciogenic Seeding of Orographic Clouds: New Observational and Modeling Tools to Study an Old Problem

这是一项被称为ASCII （AgI播云影响调查）的实地活动，旨在调查冰川播云如何影响冬季地形云的云和降水物理特性。ASCII利用了怀俄明州的一个可操作的云播种项目，并将部署机载多普勒剖面云雷达和激光雷达。该项目将对经过验证的新仪器的数据分析与高分辨率云和气溶胶解析模拟相结合，以评估该模型，了解冰核注入如何影响相互竞争的微物理过程，并评估上游条件(湿度、温度、稳定性、冰核和云凝结核浓度)影响了地面生冰播种对云性质和地面降水的影响。它还研究了在混合相地形云中可能对降水形成很重要的两个过程，即边界层湍流和表面诱导的冰起裂。知识价值：降水增强的验证已被证明是极其困难的，部分原因是与信号的强度相比，自然降水云系统中的“噪声”水平很高。然而，在过去的二十年中，已经开发出新的工具，以更有效地研究云播播的影响，特别是地形云的地面冰川播播。一方面，有了新的观测工具，特别是机载云雷达和激光雷达，可以详细观察复杂地形上方的过程，那里是大多数天然水流星生长的地方。另一方面，在气溶胶和云过程的数值模拟方面取得了巨大进展，现在可以模拟冰核播种过程。可以对模型输出进行处理，使模拟可以直接与复合雷达和激光雷达数据进行比较。这项研究不仅涉及到冰川云播种增强降水有效性的实际问题，而且涉及到更广泛的问题，即云活性气溶胶的浓度如何影响云的降水效率，从而影响气候系统的潜热强迫和辐射热强迫。后一个问题是非常复杂的，因此可以通过相对控制的实验，如冰川云播种，有效地解决。更广泛的影响：播云是最广泛使用的人工影响天气的方法，主要是为了增强降水。值得注意的是，尽管对自然云和降水过程进行了一系列有针对性的野外活动和比野外工作更强的实验控制，但播云在增强降水方面的有效性仍然不确定。尽管如此，人工降雨增加降水仍然是一项蓬勃发展的商业活动，考虑到水资源有限地区的水成本，这表明了潜在的高收益。我们相信，该项目将为在地形云中注入冰核如何影响云的性质和地表降水提供新的思路。实地工作将训练几名研究生掌握大气测量技术。

This is a field campaign, referred to as ASCII (AgI Seeding of Clouds Impact Investigation), to investigate how glaciogenic seeding affects the cloud and precipitation physics of winter orographic clouds. ASCII takes advantage of an operational cloud seeding project in Wyoming and will deploy an airborne Doppler profiling cloud radar and lidar. This project combines the analysis of data from new yet proven instruments with high-resolution cloud- and aerosol-resolving simulations, in order to evaluate the model, to understand how competing microphysical processes are affected by the injection of ice nuclei, and to assess how upstream conditions (moisture, temperature, stability, ice nuclei and cloud condensation nuclei concentrations) influence the impact of ground-based glaciogenic seeding on cloud properties and surface precipitation. It also examines two processes that may be important in precipitation formation in mixed-phase orographic clouds, i.e. boundary-layer turbulence and surface-induced ice initiation.Intellectual merit: Verification of precipitation enhancement has proven to be extremely difficult, in part because of a high level of "noise" in naturally precipitating cloud systems, compared to the magnitude of the signal. Yet in the past two decades new tools have been developed to more effectively study the impact of cloud seeding, in particular ground-based glaciogenic seeding of orographic clouds. On the one hand, there are new observational tools, in particular airborne cloud radars and lidars, allowing a detailed view of processes just above the complex terrain, where most of the natural hydrometeor growth occurs. On the other hand, dramatic advances in the numerical modeling of aerosol and cloud processes now enable the simulation of the ice nuclei seeding process. Model output can be processed such that simulations can be compared directly with composite radar and lidar data. This study is relevant not only to the practical question of efficacy of precipitation enhancement by means of glaciogenic cloud seeding, but also to the much broader question about how the concentration of cloud-active aerosol affects the precipitation efficiency of clouds, thereby affecting the latent and the radiative heat forcing of the climate system. The latter question is very complex, and thus can be productively addressed by means of relatively controlled experiments such as glaciogenic cloud seeding.Broader Impacts: Cloud seeding has been the most widely practiced method of advertent weather modification, mainly with the purpose of enhancing precipitation. It is remarkable that notwithstanding a series of targeted field campaigns and the stronger experimental control than in field work dealing with natural cloud and precipitation processes, the effectiveness of cloud seeding in enhancing precipitation remains uncertain. Nonetheless, seeding clouds to enhance precipitation remains a thriving commercial activity, which simply points to the high potential benefit, given the cost of water in water-limited regions. We are confident that the project will shed new light into how the injection of ice nuclei in orographic clouds affects cloud properties and surface precipitation. The field work will train several graduate students in atmospheric measurement techniques.