Collaborative Research: SGER--Measurements of Particle Size and Fall Velocity Distributions within Supercell Thunderstorms

调查人员将开发一个独特的移动和可快速部署的低成本激光盘状仪仪器网络，用于在2009年春季龙卷风实验2(VORTEX2)活动的第一年期间，在严重风暴中收集现场微物理数据。将与VORTEX2的其他组成部分协调测量，以便能够融合数据源，以便更全面地恢复风暴的近地表浮力、微物理组成和运动学。众所周知，强风暴的微物理成分对风暴的演变和行为有重大影响，特别是通过控制风暴下的冷池特征。虽然极化雷达观测可以提供与风暴微物理特征有关的信息，但被认为对龙卷风发生最重要的近地表环境的微物理通常低于甚至移动极化雷达平台的雷达视线。微物理可以在近地表浮力趋势中发挥关键作用，最近的几项研究表明，这可能会调节龙卷风发展的可能性。因此，需要对降雨下沉气流中的近地表微物理进行现场测量，以确定冷池浮力特征，并推断与在地表上方收集的偏振雷达观测的关系。这项研究将有助于更好地理解风暴微物理、强风暴下的冷池特征和风暴行为之间的关系。这项研究的智力价值来自于与移动极化雷达协调的严重风暴中的新的现场微物理数据收集方法。将以协作的方式同时探索部署光学盘状仪的两种方法，以最大限度地收集数据。在严重风暴中获取数据存在相当大的挑战和危险。这一努力标志着已知的第一次尝试通过盘状仪网络现场收集近表面颗粒尺寸分布的测量结果。收集到的观测将使我们能够根据VORTEX2的几个关键焦点，重新理解严重风暴的微物理特征及其行为之间的关系。这项工作的更广泛影响包括提高了对严重风暴行为的可预测性。预计这将产生于对风暴演变对微物理特征的依赖的更好理解，到目前为止，微物理特征仍然相对未知。更好地了解严重的风暴行为最终可以带来更及时、更准确的警告，从而拯救生命并留出更多时间来保护财产。此外，为该项目开发的仪器套件也将非常适合应用于其他类型的沉淀系统中的粒度分布测量。对风暴尺度数值天气预报模式中使用的微物理参数的核实也将受益于部分由测量提供的核实数据。粒度分布测量还将有助于移动雷达的校准和衰减测量。该项目将使研究生有机会参与数据收集工作，作为主要实地活动的一部分。

The investigators will develop a unique network of mobile and rapidly deployable low-cost laser disdrometer instruments for the collection of in situ microphysical data within severe storms during the first year of the Verification of the Origins of Tornadoes Experiment 2 (VORTEX2) campaign in spring of 2009. Measurements will be coordinated with other VORTEX2 components enabling fusion of data sources for a more complete retrieval of the near surface buoyancy, microphysical composition and kinematics of the storm. The microphysical composition of severe storms is known to have significant impacts on storm evolution and behavior, particularly by controlling the cold pool characteristics beneath the storm. While polarimetric radar observations can provide information related to the microphysical character of a storm, the microphysics of the near surface environment, believed to be most important for tornadogenesis, is usually below the radar horizon of even mobile polarimetric radar platforms. Microphysics can play a key role in near surface buoyancy tendency which several recent studies have shown may modulate the likelihood of tornado development. As such, in situ measurements of near surface microphysics within rainy downdrafts are needed in order to determine cold pool buoyancy characteristics and to infer relations with polarimetric radar observations collected above the surface. The research will lead to a greater understanding of the relationship between storm microphysics, cold pool characteristics beneath severe storms and storm behavior. The intellectual merit of the research stems from the novel in situ microphysical data collection method within severe storms coordinated with mobile polarimetric radars. Two methods for optical disdrometer deployment will be simultaneously explored in a collaborative approach to maximize data collection. There are considerable challenges and hazards associated with data acquisition within severe storms. This effort marks a first known attempt to collect in situ near surface measurements of particle size distributions by a network of disdrometers. The collected observations will enable new understanding of the relationship between microphysical characteristics of severe storms and their behavior in line with several key foci of the VORTEX2. The Broader impacts of the work include improved predictability of severe storm behavior. This is expected to emerge from a better understanding of storm evolution dependence on microphysical characteristics, which to date remains relatively unknown. Better understanding of severe storm behavior can ultimately lead to more timely and accurate warnings that can save lives and allow additional time to protect property. Further, the developed instrumentation suite for this project will also be quite suitable for application to particle size distribution measurements in other types of precipitating systems. The verification of microphysical parameterizations used in storm-scale numerical weather prediction models also would benefit from verification data provided in part by the measurements. Particle size distribution measurements will also aid in mobile radar calibration and attenuation metrics. This project will enable graduate students opportunities to participate in data collection efforts as part of a major field campaign.