Synergistic Studies of Raindrop Shapes, Oscillations and Orientations Using 2D-Video Disdrometer, Advanced Radar and Wind Tunnel

这项研究解决了一些与雨微结构有关的关键科学问题，这里定义的微结构是指各种降雨类型和气候中雨滴的大小、形状和取向分布。虽然在理解雨滴大小分布的可变性方面取得了很大的进展，在使用平均水滴形状和取向分布的“整体”假设方面也取得了一定的成功，但雨滴形状分布参数和振荡模式的变化仍然没有完全被理解。关于下降倾斜角分布的可变性的观测就更少了。对这些雨微结构特征的了解是开发基于偏振雷达的准确的雨滴尺寸分布和雨率反演以及电磁波衰减校正算法的关键。这项研究是由观测驱动的，利用了不同地点(阿拉巴马州亨茨维尔和澳大利亚布里斯班)的多个2D视频碟形仪和先进的雷达，包括阿拉巴马州亨茨维尔的双极化装甲雷达、布里斯班的双波长/双极化CP2雷达和科罗拉多州格里利附近的双极化CSU-CHILL雷达。位于德国美因茨的约翰尼斯·古滕贝格大学的世界级垂直风洞设施将用于专门观测自由“漂浮”水滴的时变形状和振荡模式，以及调查中到大水滴与亚毫米水滴合并后的时变形状。这项研究的更广泛影响是：(A)国家气象局业务天气雷达网和“填补缺口”X波段雷达即将进行极化升级，从而更好地利用新的观测能力，用于短程水文应用；(B)纳入新的结果，以改进美国许多电视台正在计划将其C波段系统升级为双极化系统以改进恶劣天气预报所使用的雷达显示器，以及(C)国家和国际无线电波传播界使用关于液滴形状和方向的结果。

This research addresses a number of key science questions related to rain microstructure defined herein as the size, shape and orientation distributions of raindrops in a wide range of rain types and climatologies. Whilst great progress has been made in the understanding of drop size distribution variability, and there has been modest success in the use of "bulk" assumptions on mean drop shapes and orientation distributions, there are still variations in the raindrop shape distribution parameters and oscillation modes that are not fully understood. There are even fewer observations of the variability of the drop canting angle distribution. Knowledge of these rain microstructure characteristics is key to developing accurate polarimetric radar-based drop-size distribution and rain rate retrievals, and for electromagnetic wave attenuation-correction algorithms.This research is observationally-driven and makes use of multiple 2D-video disdrometers in different locations (Huntsville, AL and Brisbane, AU) and advanced radars including the dual-polarized ARMOR radar in Huntsville, AL; the dual-wavelength/dual-polarized CP2 radar in Brisbane, and the dual-polarized CSU-CHILL radar near Greeley, CO. The world class vertical wind tunnel facility at the Johannes Gutenberg-Universität in Mainz, Germany will be used for specialized observation of the time varying shapes and oscillation modes of freely "floating" drops, as well as an investigation into the time varying shapes of moderate-to-large drops after coalescing collisions with sub-millimetric sized drops.The broader impacts of the study are: (a) better use of new observing capability resulting from the imminent polarimetric upgrade of the National Weather Service operational weather radar network and "gap-filler" X band radars for short range hydrological applications; (b) incorporation of new results to improve radar displays used by many TV stations in the US that are planning to upgrade their C-band systems to dual-polarization to improve severe weather forecasting, and (c) use of results on drop shapes and orientations by the national and international radiowave propagation community.