Abstract This study investigates the impacts of black carbon (BC) properties (vertical concentration, shape, size, and mixing state) and atmospheric variables (cloud and aerosol loading, surface albedo, and solar zenith angle) on BC radiative effects. Observations from aircraft measurements, lidar, and the Aerosol Robotic Network (AERONET) are used to constrain BC and aerosol properties. The library for radiative transfer (Libradtran) model is used to calculate BC radiative forcing (RF). BC optical properties are obtained from numerical modeling with aggregate or spherical structures and different size distributions. By modifying the optical properties, different BC geometries and size distributions result in uncertainties in RF and heating rate less than 30%, while the uncertainty in heating rate due to different BC mixing states is as large as ~80%. The vertical distribution of BC concentrations explains less than 10% of the relative differences in RF and heating rate in the atmosphere, but can induce different heating rate vertical profiles, thus different planetary boundary layer (PBL) stabilities. Due to the significant influence of cloudy and aerosol conditions on incident solar radiation, atmospheric conditions play an important role in determining the BC heating rate. Meanwhile, the effects of surface albedo and solar zenith angle on the BC heating rate are most significantly near the surface. Taking the above factors into account, we introduce an empirical approximation of the BC heating rate to estimate its influence on the atmosphere. With the simple formula, the BC heating rate for a particular atmospheric layer can be approximated when the vertical condition is known, and this can be further applied to determine whether BC promotes or suppresses PBL development. Considering the importance of the BC vertical concentration in its heating rate, we suggest that light-absorbing aerosols and their vertical distributions must be better measured and modeled to improve the understanding of their radiative effects and interaction with PBL.

中文翻译：

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黑碳气溶胶引起的大气升温速率：不确定性和影响因素

摘要 本研究调查了黑碳 (BC) 特性（垂直浓度、形状、大小和混合状态）和大气变量（云和气溶胶载荷、地表反照率和太阳天顶角）对黑碳辐射效应的影响。来自飞机测量、激光雷达和气溶胶机器人网络 (AERONET) 的观察结果用于限制 BC 和气溶胶特性。辐射传递库 (Libradtran) 模型用于计算 BC 辐射强迫 (RF)。BC 光学特性是从具有聚集体或球形结构和不同尺寸分布的数值模型中获得的。通过修改光学特性，不同的 BC 几何形状和尺寸分布导致 RF 和加热率的不确定性小于 30%，而由于不同的 BC 混合状态，加热速率的不确定性高达 ~80%。BC 浓度的垂直分布解释了大气中 RF 和加热速率的相对差异不到 10%，但会导致不同的加热速率垂直剖面，从而导致不同的行星边界层 (PBL) 稳定性。由于多云和气溶胶条件对入射太阳辐射的显着影响，大气条件在确定 BC 加热速率方面起着重要作用。同时，地表反照率和太阳天顶角对 BC 加热速率的影响在地表附近最为显着。考虑到上述因素，我们引入了 BC 加热速率的经验近似值来估计其对大气的影响。用简单的公式，当垂直条件已知时，可以近似特定大气层的 BC 加热速率，这可以进一步应用于确定 BC 是促进还是抑制 PBL 发展。考虑到 BC 垂直浓度对其加热速率的重要性，我们建议必须更好地测量和模拟吸光气溶胶及其垂直分布，以提高对其辐射效应和与 PBL 相互作用的理解。