Scattering From Ice Crystals for Millimeter-Wave Radar Remote Sensing of Clouds

用于毫米波雷达云遥感的冰晶散射

• 批准号: 9813512
• 负责人: Kultegin Aydin
• 金额: $ 22.53万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-01-01 至 2002-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9813512&HistoricalAwards=false
• 关键词: Scattering; Ice; Crystals; Millimeter; Wave

This project will extend the work on millimeter-wave scattering by ice crystals that was initiated in a previous NSF Grant, ATM-9225116. The objective is to evaluate the scattering characteristics of ice crystals having many different shapes and sizes to aid in the interpretation of polarimetric radar observations of ice clouds. The approach is to calculate the scattering from ice crystals and to compare the results with experimental measurements using mm-wave radars and airborne cloud-sampling equipment. The calculations will be for three different radio frequencies, corresponding to those in use on short-wavelength radars: 35, 94, and 220 GHz (corresponding to wavelengths of 8.6, 3.2, and 1.4 mm). Because the wavelengths are comparable to the size of ice crystals, the Rayleigh or the geometric optics approximations for scattering cannot be used. Instead, the Waterman T-matrix approach will be used for crystals that have no dimension larger than 0.1 mm and the computationally intensive finite-difference time domain (FDTD) method for all crystals larger than this size. The scattering properties of clouds of ice crystals will be computed by integrating over a range of crystal sizes approximated by either gamma distributions or bimodal distributions, both of which have been found to describe cloud populations. The calculations will include all measurable polarization parameters, such as vertical and horizontal reflectivity factors, differential reflectivity, differential phase shift, and copolarized correlation coefficient. Comparison of the computed results with radar observations will be made through collaboration with groups at the University of Wyoming, the University of Massachusetts at Amherst, and the meteorology department at Penn State. The goal of the work is to develop a method to estimate crystal habit and cloud ice content by radar. The results would have application to both remote sensing and the parameterization of radiative transfer by ice clouds in large scale numerical models of the atmosphere.

该项目将通过冰晶散射的毫米波散射的工作扩展，该冰晶是在以前的NSF赠款ATM-9225116中启动的。 目的是评估具有许多不同形状和大小的冰晶的散射特性，以帮助解释冰云的偏振雷达观测值。 该方法是计算冰晶的散射，并将结果与​​使用MM波雷达和空中云采样设备进行实验测量进行比较。 计算将用于三个不同的无线电频率，与短波长雷达上使用的频率相对应：35、94和220 GHz（对应于8.6、3.2和1.4 mm的波长）。 由于波长与冰晶的大小相当，因此无法使用雷利或几何光学近似值。 取而代之的是，Waterman T-Matrix方法将用于没有大于0.1 mm的尺寸的晶体，并且用于大于此尺寸的所有晶体的计算强度有限差分时间域（FDTD）方法。 冰晶云的散射特性将通过在通过伽马分布或双峰分布近似的一系列晶体大小上进行集成来计算，这两种分布都被发现以描述云种群。 计算将包括所有可测量的极化参数，例如垂直和水平反射率因子，差异反射率，差异相位移位以及共可极化的相关系数。 将通过与怀俄明大学，阿默斯特大学的马萨诸塞大学和宾夕法尼亚州立大学的气象学的团体合作进行计算结果与雷达观察的比较。 这项工作的目的是开发一种方法来估算雷达的晶体习惯和云冰含量。 结果将在大气的大规模数值模型中应用于遥感和辐射传递的参数化。