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 atmospheric research, 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.
