A New Approach to Electromagnetic Scattering from Ice Crystal Aggregates for Improving Quantitative Radar Measurements of Clouds and Precipitation

冰晶聚集体电磁散射的新方法可改善云和降水的定量雷达测量

• 批准号: 1228180
• 负责人: Kultegin Aydin
• 金额: $ 49.62万
• 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: 2012
• 资助国家: 美国
• 起止时间: 2012-11-01 至 2017-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1228180&HistoricalAwards=false
• 关键词: New; Approach; Electromagnetic; Scattering; Ice

The goal of this research is to improve the qualitative and quantitative interpretation of radar measurements of clouds and precipitation composed of ice crystals and their aggregates. Aggregates are the dominant ice phase contributors to the area fraction of precipitation across the globe. Satellite radar systems and a growing number of ground-based research radars in the U.S. and around the world operate at millimeter wave frequencies and are focused on the qualitative and quantitative characterization of clouds. Recent studies have suggested errors in excess of an order of magnitude in the millimeter-wave radar cross sections of aggregates. A new approach to modeling aggregates provides a pathway to efficiently and accurately determine radar cross sections from irregular shaped particles. An improved accuracy of radar cross section calculations of ice particles is necessary to enhance our understanding of millimeter wave radar observations of stratiform clouds, melting layer, and ice precipitation. This research will be accomplished through a new modeling approach for studying the electromagnetic scattering characteristics of ice crystal aggregates. Advances in computer technology and computational algorithms have made it possible to evaluate millimeter wave scattering from pristine crystals with well defined shapes and composition. Irregularly shaped hydrometeors such as ice crystal aggregates (snowflakes) have been modeled as homogeneous particles with spherical or spheroidal shapes through an effective medium approximation of their dielectric constants. It has recently been shown that at millimeter wavelengths this "bulk" model approach for ice crystal aggregates leads to significant underestimation of their radar cross sections. This study models the complex shape and composition of aggregates using pristine crystal types that appear in nature (e.g., needles, columnar crystals, dendrites, bullet rosettes). The pristine crystals that makeup the aggregates are constructed using tiny ice spheres. An established computational algorithm is used to evaluate the electromagnetic scattering characteristics of the aggregates constructed in this manner.Intellectual merit: This research brings a new and efficient approach to accurately characterizing electromagnetic scattering from ice hydrometeors, which will be used for simulating millimeter wave radar observations of clouds and developing algorithms for the interpretation radar measurements.Broader impacts: Results from this study will find application in surface and space-based remote sensing of clouds and precipitation, satellite communication link design, and weather research. A graduate student and a postdoctoral fellow will participate in these research activities. They will be trained in both theoretical and experimental methodologies and techniques necessary for conducting the research. The generated electromagnetic scattering data will be made available to the research community through a database maintained on the web.

这项研究的目的是改善对云层和由冰晶体及其聚集体组成的雷达测量值的定性和定量解释。 聚集体是全球降水区域的主要造成冰期贡献者。 卫星雷达系统和越来越多的地面研究雷达在美国及其各地的雷达系统以毫米波频率运行，并着重于云的定性和定量表征。最近的研究表明，在骨料的毫米波雷达横截面中，误差超过了数量级。 建模骨料的新方法为有效，准确地确定不规则形状颗粒的雷达横截面提供了一种途径。 为了增强我们对层状云，熔融层和冰降压的毫米波雷达观测值的理解，需要提高冰粒横截面计算的精度。这项研究将通过一种新的建模方法来研究冰晶骨料的电磁散射特征。 计算机技术和计算算法的进步使得从具有良好形状和组成的原始晶体中评估毫米波散射成为可能。 不规则形状的水星（例如冰晶骨料（雪花））已通过有效的介质常数近似值近似为具有球形或球形形状的均匀颗粒。最近已经显示，在毫米波长下，这种冰晶体聚集体的“大量”模型方法导致其雷达横截面的明显低估。这项研究使用出现在自然界中的原始晶体类型（例如针，柱状晶体，树突，子弹玫瑰花结）对聚集体的复杂形状和组成进行了建模。构成聚集体的原始晶体是使用微小的冰球构建的。既定的计算算法用于评估以这种方式构建的聚集体的电磁散射特征。智能优点：这项研究为从冰磁铁中的电磁散射提供了一种新的和有效的方法，该方法将用于从冰冰淇淋中表征电磁体的电磁散射，这些方法将用于模拟毫米的云范围，以进行千分之一的范围，以进行千分之一的范围。研究将在云层和降水，卫星通信链路设计和天气研究的表面和空间遥感中找到应用。研究生和博士后研究员将参加这些研究活动。它们将接受进行研究所需的理论和实验方法和技术的培训。生成的电磁散射数据将通过网络上的数据库提供给研究社区。