Collaborative Research: Characterization of the Two-dimensional/Temporal Mosaic of Drop Size Distributions and Spatial Variability (Structure) in Rain

降水颗粒分布的特征尺度和结构一般都是在远大于1公里的尺度上探索的，但出于几个原因，必须在小得多的尺度上表征它们的变异性。这些措施包括：(1)优化对简单雨量计和滴度计观测结果的解释，并将这种测量转换到更大的尺度，以验证数值天气预报和洪水警告；(2)更好地了解多维背景下的水滴相互作用和演变，而不仅仅是对降水的垂直依赖的经典处理(通常被认为足以表示包括雨滴碰撞、合并和解体在内的过程)；(3)更完整地描述雷达发射的微波如何与降雨相互作用；以及(4)最终将雨滴大小分布的一维观测结果连接并转换到更大的二维域。该项目的智能优势来自于通过结合使用二维视频碟形仪和联网的光学碟形仪阵列来量化小规模降水结构，研究人员将通过该阵列计算降雨中的对相关函数，以得出任何给定降水场水平几何形状的改进测量。盘状仪观测(其水平间隔可以很容易地调整)还将允许检查大范围的距离，以确定可能的尺度、自相似性和液滴大小分布的功能结构，以便更好地与覆盖大片地区的降水遥感测量相联系。这项工作的总体目标是收集和分析水平尺度上的降雨量的时间序列观测，范围从厘米(使用2-D视频碟形仪观测)到几十米到可能100米或更多。更广泛的影响将来自对改进洪水预报和监测的潜在贡献，以及更好的与土壤侵蚀有关的进程，通过支持学生实际参与，以及通过改善一个服务于代表性不足群体的本科生机构的观测基础设施。

Characteristic scales and structures of precipitation particle distributions have generally been explored over dimensions considerably larger than 1 km, yet for several reasons it is important to characterize their variability on far smaller scales. These include the need to: (1) optimize interpretation of observations made by simple rain gages and disdrometers and the translation of such measurements to much larger scales, as needed for validation of numerical weather forecasts and flood warnings; (2) better understand drop interactions and evolution in a multi-dimensional context rather than just the classical time dependent treatment in the vertical for falling precipitation (as has often been considered adequate for representation of processes including raindrop collision, coalescence and break-up); (3) achieve a more complete description of how radar-emitted microwaves interact with rain; and (4) ultimate connection and perhaps translation of 1-D observations of drop size distributions to larger 2-D domains.The intellectual merit of this project derives from quantification of small-scale precipitation structures via combined use of a 2-D video disdrometer in conjunction with a networked array of optical disdrometers, through which investigators will calculate pair-correlation functions in rain to derive improved measures of any given precipitation field's horizontal geometry. Disdrometer observations (whose horizontal separation may be readily adjusted) will also allow examination a wide range of distances for possible scaling, self-similarity and functional structures of drop size distributions so as to better connect with remote-sensor measurements of precipitation covering large areas. The over-arching objective of this work is to collect and analyze time-series observations of rainfall over horizontal scales ranging from centimeters (as observed using a 2-D video disdrometer) up to several tens to perhaps a hundred meters or more. Broader Impacts will come through potential contributions to improved flood prediction and monitoring as well as better processes relevant to soil erosion, through support of hands-on student involvement in, and through improved observational infrastructure at an undergraduate institution serving underrepresented groups.