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增温剂。然而，其通过减少冰雪反照率而产生的辐射强迫目前具有很大的不确定性。本研究旨在通过提高对bc -雪辐射相互作用的理解，开发并实现bc -雪系统光谱光学特性的参数化，以解决这一不确定性，该参数化考虑了非球形雪粒形状和bc -雪随机混合的紧密堆积雪粒。参数化将在地表模式中实现，以提高我们对bc -雪辐射及其对地表温度、水循环和地表水收支的反馈的理解。本研究将开展大气黑碳（BC）和积雪系统辐射传输的基础研究，以了解积雪反照率降低及其在陆面模式中的潜在应用。本研究将探讨雪粒堆积对传统独立散射近似的影响，该近似通常用于行星大气的辐射传输，对降低雪反照率至关重要。该研究还将开发一种基于物理的光谱（0.2 - 5微米）光学特性的参数化方法，涉及大气BC颗粒（尺寸范围为0.01 - 0.1微米和核壳结构）和雪颗粒（尺寸范围为50 - 1000微米，形状从雪花、板/柱到球体）的耦合。将使用几何光学和表面波（GOS）方法，并用实验室测量和其他数值方法进行验证，以获得必要和足够的数据库，以便组织适当的查找表和多项式指数函数，以便将其纳入陆地表面模型。BC-雪系统的混合状态也将根据先前EAGER奖开发的方法进行研究，该方法使用单球和核壳球作为构建块，用于雪颗粒中的BC颗粒的外部（干沉积）和内部（湿沉积）多重混合物。第四个目标包括利用通过BC省大气和穿透雪层的太阳辐射传输，使用精确的加/加倍方法，但为了与陆地表面模式中包含的方法一致，使用2流近似。诺亚多参数化（诺亚- mp）将在天气研究与预报（WRF）模式的背景下使用。

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.