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

传统的模拟大气颗粒物光学性质的T-矩阵方法是基于扩展的边界条件(以下简称EBC-TM)的，该方法涉及粒子表面的积分，对表面不连续性很敏感，例如尖锐的边缘和拐角。在实践中，EBC-TM主要应用于有限尺寸参数范围内的规则几何形状，如椭球体、圆柱体和切比雪夫粒子。不变嵌入T矩阵(II-TM)方法在概念上不同于EBC-TM方法，它源于基于体积的电磁积分。初步研究(Bi.Yang等人，2013年)表明，II-TM可以应用于比EBC-TM更宽的尺寸参数范围。此外，从实用的角度来看，II-TM可以应用于一般的非球形和非均匀形态(注意，这种可行性已经在六角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、受污染的尘埃颗粒、与硫酸盐混合的烟尘集合体、带有气泡或黑碳夹杂的冰晶、中空冰晶以及具有表面粗糙度的集合体冰晶的光学性质。作为光散射界的有用工具，II-TM模型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，还将利用精确建模功能模拟太阳至红外区域的纯尘和污染尘埃以及微波区域的冰晶、雪花和颗粒的光学性质数据库。智能优点：II-TM程序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，以指导各种数值和近似方法的进一步发展。该项目的成果可能大大提高目前对两种主要大气颗粒物--尘埃气溶胶和冰晶--光学性质的认识水平。纯尘埃和污染尘埃以及冰晶、雪花和冰粒的散射和偏振特性数据库将立即在大气研究中找到下游应用，特别是在遥感和辐射传输模拟中。广泛影响：II-TM模型将直接有助于减少尘埃和冰晶光学属性中的不确定性，这些光学属性对于从不同角度研究空气中的尘埃和冰云至关重要，包括大气遥感和辐射强迫评估，并可能在其他学科中找到应用，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尘埃气溶胶的研究。此外，该项目将有一个重要的教育组成部分，重点是指导博士后研究人员、培训研究生和开发教学工具。

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.