Development of Rigorous Computational Capabilities Based on the Invariant Imbedding Principle for the Simulation of the Optical Properties of Dust and Ice Crystals

传统的模拟大气粒子光学特性的t矩阵方法由Waterman（1972）首创，并由其他人（例如Mishchenko和Travis， 1994）进一步发展，它基于扩展边界条件（以下简称EBC-TM），涉及粒子表面上的积分，这对表面不连续性（如锋利的边缘和角落）很敏感。在实践中，EBC-TM主要应用于在有限尺寸参数范围内的规则几何形状，如球体、圆柱体和切比雪夫颗粒。与EBC-TM在概念上不同，不变嵌入t矩阵（II-TM）方法源于基于体积的电磁积分。一项初步研究（Bi, Yang et al., 2013）表明，II-TM可以应用于比EBC-TM更宽的尺寸参数范围。此外，从实际应用的角度来看，II-TM可以应用于一般的非球形和非均匀形貌（注意，这种可行性已经在六边形冰晶的情况下得到了证明）。该奖项的目标是开发一个严格的II-TM包，以准确模拟假设的不规则尘埃颗粒、污染尘埃颗粒、混合硫酸盐的烟尘聚落、带有气泡或黑碳夹杂物的冰晶、空心冰晶和表面粗糙度的聚落冰晶的光学特性。II-TM模型作为光散射学界的有用工具，将为评估各种数值方法和半经典方法的数值性能提供基准参考。此外，将利用精确的建模能力模拟纯尘和污染尘在太阳-红外波段的光学特性数据库，以及冰晶、雪花和霰粒子在微波波段的光学特性数据库。智力优势：II-TM包将代表最先进的光散射计算能力，这将有助于建立基准参考，指导各种数值和近似方法的进一步发展。该项目的结果可能会大大提高目前对两种主要大气颗粒物，粉尘气溶胶和冰晶的光学特性的认识水平。纯尘和污染尘、冰晶、雪花和霰粒子的散射和极化特性数据库将在大气研究中，特别是在遥感和辐射传输模拟中找到直接的下游应用。更广泛的影响：II-TM模式将直接有助于减少尘埃和冰晶光学特性的不确定性，这对从大气遥感和辐射强迫评估等各个角度研究空气中的尘埃和冰云至关重要，并可能在其他学科中得到应用，例如生物光学。特别是，将在网上传播的数据库将立即应用于许多研究人员涉及冰云和粉尘气溶胶的研究。此外，该项目将有一个重要的教育组成部分，重点是指导一名博士后研究员，培训一名研究生，并开发教学工具。

The conventional T-matrix method to simulate the optical properties of atmospheric particles, pioneered by Waterman (1972) and further developed by others (e.g., Mishchenko and Travis, 1994), is based on the extended boundary conditions (hereafter, EBC-TM) involving integration over the particle surface, which is sensitive to surface discontinuities such as sharp edges and corners. In practice, the EBC-TM is primarily applied to regular geometries such as spheroids, circular cylinders, and Chebyshev particles over a limited size parameter range. Conceptually different from the EBC-TM, the invariant imbedding T-matrix (II-TM) method stems from volume-based electromagnetic integration. A preliminary study (Bi, Yang et al., 2013) has demonstrated that the II-TM can be applied to a much wider size parameter range than the EBC-TM. Moreover, from a practical perspective, the II-TM is feasible to be applied to general nonspherical and inhomogeneous morphologies (note, the feasibility has been demonstrated in the case of hexagonal ice crystals). The goal of this award is to develop a rigorous II-TM package to accurately simulate the optical properties of assumed irregular dust particles, polluted dust particles, soot aggregates mixed with sulfate, ice crystals with air bubbles or black carbon inclusions, hollow ice crystals, and aggregate ice crystals with surface roughness. As a useful tool for the light scattering community, the II-TM model will provide a benchmark reference to assess the numerical performance of various numerical approaches and semi-classical approaches. Furthermore, databases of the optical properties of pure and polluted dust in the solar-to-infrared regime and of ice crystals, snow flakes, and graupel particles in the microwave regime will be simulated by using the accurate modeling capabilities.Intellectual Merit :The II-TM package will represent state-of-the-science light scattering computational capabilities, which will facilitate the establishment of a benchmark reference to guide the further development of various numerical and approximate methods. The outcome of this project may substantially enhance the current level of knowledge about the optical properties of two prominent atmospheric particulate matters, dust aerosols and ice crystals. Databases of the scattering and polarization properties of pure and polluted dust and of ice crystals, snowflakes, and graupel particles will find immediate downstream applications in atmosphericresearch, particularly, in remote sensing and radiative transfer simulations.Broader Impacts :The II-TM model will directly contribute to the reduction of the uncertainties in the optical properties of dust and ice crystals that are critical to the study of airborne dust and ice clouds from various perspectives including the atmospheric remote sensing and radiative forcing assessment, and may find applications in other disciplines, e.g., bio-optics. Particularly, the database that will be disseminated on-line will have immediate applications to the studies involving ice clouds and dust aerosols by many researchers. Furthermore, this project will have a significant educational component focused on mentoring a postdoctoral researcher, training a graduate student, and developing teaching tools.