Radiative Transfer through the Black Carbon-Snow System: Fundamentals and Applications

黑碳（BC）已被确定为大气中重要的变暖因子。然而，其辐射强迫通过减少雪/冰覆盖，目前与很大的不确定性。该研究旨在解决这种不确定性，通过提高对BC雪辐射相互作用的理解，并开发和实施BC雪系统的光谱光学特性的参数化，考虑非球形雪粒形状，以及BC雪随机混合的紧密堆积雪粒。 参数化将在陆面模式中实施，以提高我们对BC雪辐射和地表温度，水文循环和地表水收支反馈的理解。本研究将对通过大气黑碳（BC）和雪系统的辐射传输进行基础研究，以了解雪的减少及其在陆面模型中的潜在应用。 这项研究将调查传统的独立散射近似，通常用于在行星大气中的辐射传输，关键的雪粒子堆积的影响。 该研究还将为光谱（0.2 - 5微米）光学特性开发基于物理的参数化，涉及大气BC颗粒的耦合，尺寸范围从0.01 - 0.1微米和核壳结构，以及雪粒，尺寸从50 - 1000微米，形状从雪花，通过板/柱，到球体。 几何光学和表面波（GOS）的方法将被用来验证实验室测量和其他数值方法，以获得必要的和足够的数据库，组织适当的查找表和多项式指数函数容易纳入陆面模型。 BC-雪系统的混合状态也将根据先前的EAGER奖开发的方法进行研究，该EAGER奖用于外部（干沉积）和内部（湿沉积）BC颗粒在雪粒中的多种混合物，使用单个和核壳球体作为构建块。 第四个目标包括通过BC大气和穿透雪层的太阳辐射传输的使用，使用精确的增加/加倍方法，但与2流近似一致的方法包括在陆面模型。 Noah多参数化（Noah-MP）将在天气研究和预报（WRF）模型的范围内使用。

Black carbon (BC) has been identified as an important warming agent in the atmosphere. However, its radiative forcing through reducing the snow/ice albedo is currently associated with large uncertainty. The study seeks to address this uncertainty by improving the understanding of the BC-snow-radiation interactions and developing and implementing a parameterization for the spectral optical properties of BC-snow system accounting for the non-spherical snow grain shapes, and close-packed snow grains with BC-snow stochastic mixing. The parameterization will be implemented in a land surface model to improve our understanding of BC-snow-radiation and feedbacks on the surface temperature, hydrological cycle, and surface water budget. This study will conduct fundamental research on radiative transfer through atmospheric black carbon (BC) and snow systems to understand snow albedo reduction and its potential application to land surface models. This study will investigate the impact of snow-grain packing on the conventional independent scattering approximation, commonly employed for radiative transfer in planetary atmospheres, critical to snow albedo reduction. The study will also develop a physically-based parameterization for the spectral (0.2 - 5 micron) optical properties involving the coupling of atmospheric BC particles, with sizes ranging from 0.01 - 0.1 micron and core-shell structures, and snow grains, with sizes spanning from 50 - 1000 micron and shapes from snowflakes, through plates/columns, to spheroids. Geometric-optics and surface-wave (GOS) approach will be used, verified with laboratory measurements and other numerical methods, to derive necessary and sufficient databases to organize suitable lookup tables and polynomial-exponential functions readily for incorporation into a land surface model. The mixing state of the BC-snow system will also be investigated following the approach developed under a previous EAGER award for external (dry deposition) and internal (wet deposition) multiple mixtures of BC particles in snow grains using single and core-shell spheres serving as building blocks. A fourth objective includes the use of solar radiative transfer through the BC atmosphere and penetrating snow layers, using the exact adding/doubling method, but with the 2-stream approximation for consistence with the methodology included in land surface models. Noah multi-parameterizations (Noah-MP) will be used within the context of the Weather Research and Forecasting (WRF) model.