Field Studies of Raindrop Axis Ratio Distributions Using an Improved 2D-Video Disdrometer and Dual-Polarized Radar

这笔赠款是该研究小组在国家科学基金会支持下开展的工作的延续，利用该赠款下获得的数据、分析程序和结果。这项研究的新方面是使用Profile 2D-Video Disdroeter(2DVD)来表征各种降雨条件下的液滴轴比分布，同时使用同时扫描的双偏振和垂直指向的多普勒雷达观测来表征相同降雨事件的垂直剖面。有关尺寸、形状和垂直剖面的综合数据对于理解现有极化雷达降雨反演和衰减校正算法中的可变性是必要的。此外，他们还将研究强降雨中液滴振荡的碰撞强迫及其对轴比分布的影响。现有的数据集将通过在三个仪器齐全的地点进行的实地活动来扩大，这些地点涵盖了一系列的降雨气候。这些站点包括(I)科罗拉多(科罗拉多州普莱特维尔站点30公里的CSU寒冷雷达S)，(Ii)冲绳副热带研究中心(C波段眼镜蛇极化雷达东北15公里的Ogimi风廓线站点)和(Iii)苏门答腊岛(Koto Tabang)。现场活动和数据分析程序将集中于实现以下目标：a.雨型和雨势对雨轴比分布的影响基于衰减校正和偏振雷达的降雨反演算法的意义c。通过观测和模拟对碰撞强迫液滴振荡的评估以及对雷达算法的影响。更广泛的影响将在两个领域：(1)评估降雨恢复算法，包括将升级极化能力的运行天气雷达的衰减校正方案；(2)液滴形状和大小分布对无线电波沿视线地面系统以及地球-空间系统传播的影响。

This grant is a continuation of the NSF supported work performed by this research group, utilizing data, analyses procedures and results acquired under that grant. New aspects of this study is to characterize drop axis ratio distributions with a profile 2D-Video Disdrometer (2DVD) under a wide variety of rain conditions, while using simultaneous scanning dual polarization and vertically pointing Doppler radar observations to characterize the vertical profiles of the same rain events. The combined data on sizes, shapes and vertical profiles are necessary for understanding variability in existing polarimetric radar rain-retrieval and attenuation-correction algorithms. In addition, they will also investigate collisional-forcing of drop oscillations in strong rainfall and its subsequent effect on the axis ratio distributions.The existing data sets will be augmented through field campaigns at three well-instrumented sites that cover a range of rain climatologies. These sites include (i) Colorado (Platteville site 30 km S of CSU CHILL radar), (ii) Okinawa Sub-Tropical Research Center (Ogimi wind profiler site 15 km NE of the polarimetric C-band COBRA radar) and (iii) Sumatra (Koto Tabang).The field campaigns and data analysis procedures will be focused on achieving the following objectives:a. rain type and regime dependence of drop axis ratio distributionsb. implications for attenuation-correction and polarization radar-based rain retrieval algorithmsc. evaluation of collisionally-forced drop oscillations via observations and modeling, and impact on radar algorithms.The broader impact will be in two areas: (i) the assessment of rain retrieval algorithms, including attenuation-correction schemes for operational weather radars which will be upgraded for polarimetric capability; and (ii) implications of drop shapes and size distributions for propagation of radio waves along line-of-sight terrestrial systems as well as earth-space systems.