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

这项资助是该研究小组利用在该资助下获得的数据、分析程序和结果进行的NSF支持工作的延续。本研究的新方面是在多种降雨条件下，利用剖面2D-Video Disdrometer （2DVD）表征雨滴轴比分布，同时利用同步扫描双偏振和垂直指向多普勒雷达观测来表征相同降雨事件的垂直剖面。关于尺寸、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的变异性是必要的。此外，他们还将研究强降雨中雨滴振荡的碰撞强迫及其对轴比分布的后续影响。现有的数据集将通过在三个设备齐全的地点开展实地活动加以扩充，这些地点涵盖了一系列降雨气候学。这些站点包括(i)科罗拉多州（CSU CHILL雷达南30公里的Platteville站点），（ii）冲绳亚热带研究中心（Ogimi风剖面仪站点东北15公里的偏振c波段COBRA雷达）和（iii）苏门答腊（Koto Tabang）。外地运动和数据分析程序将集中于实现下列目标：落差轴比分布的雨型与制度关系[j]。基于衰减校正和极化雷达的降雨反演算法的意义。通过观测和建模评估碰撞强迫跌落振荡，以及对雷达算法的影响。更广泛的影响将在两个方面：(i)评估降雨检索算法，包括将为提高极化能力而升级的气象雷达的衰减校正方案；以及（ii）水滴形状和大小分布对无线电波沿视距地面系统和地球-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.