Abstract. Most of the dust models underestimate the load of the large dust particles, consider spherical shapes instead of irregular ones, and have to deal with a wide range of the dust refractive index (RI) to be used. This leads to an incomplete assessment of the dust radiative effects and dust-related impacts on climate and weather. The current work aims to provide an assessment, through a sensitivity study, of the limitations of models to calculate the dust direct radiative effect (DRE) due to the underrepresentation of its size, RI, and shape. We show that the main limitations stem from the size and RI, while using a more realistic shape plays only a minor role, with our results agreeing with recent findings in the literature. At the top of the atmosphere (TOA) close to dust sources, the underestimation of size issues an underestimation of the direct warming effect of dust of ∼ 18–25 W m−2, for DOD = 1 (dust optical depth) at 0.5 µm, depending on the solar zenith angle (SZA) and RI. The underestimation of the dust size in models is less above the ocean than above dust sources, resulting in an underestimation of the direct cooling effect of dust above the ocean by up to 3 W m−2, for aerosol optical depth (AOD) of 1 at 0.5 µm. We also show that the RI of dust may change its DRE by 80 W m−2 above the dust sources and by 50 W m−2 at downwind oceanic areas for DOD = 1 at 0.5 µm at TOA. These results indicate the necessity of including more realistic sizes and RIs for dust particles in dust models, in order to derive better estimations of the dust DRE, especially near the dust sources and mostly for studies dealing with local radiation effects of dust aerosols.

中文翻译：

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模型中尘埃光学特性参数化引起的辐射效应的敏感性研究

摘要。大多数灰尘模型低估了大灰尘颗粒的载荷，考虑球形而不是不规则形状，并且必须处理要使用的大范围灰尘折射率（RI）。这导致对沙尘辐射效应以及与沙尘相关的气候和天气影响的评估不完整。目前的工作旨在通过敏感性研究，评估计算灰尘直接辐射效应 (DRE) 的模型由于其尺寸、RI 和形状的代表性不足而存在的局限性。我们表明，主要的限制源于尺寸和 RI，而使用更真实的形状只起次要作用，我们的结果与文献中的最新发现一致。在靠近尘埃源的大气顶部 (TOA)，尺寸的低估会导致低估尘埃的直接升温效应，即 ∼ 18–25 W m−2，对于 0.5 µm 处的 DOD = 1（尘埃光学深度） ，取决于太阳天顶角 (SZA) 和 RI。模型中对海洋上方灰尘尺寸的低估小于对灰尘源上方灰尘尺寸的低估，导致当气溶胶光学深度 (AOD) 为 1 时，海洋上方灰尘的直接冷却效应被低估高达 3 W m−2 0.5微米。我们还表明，在 TOA 0.5 µm 处 DOD = 1 时，沙尘的 RI 可能会在沙尘源上方将其 DRE 改变 80 W m−2，在顺风海洋区域改变其 DRE 50 W m−2。这些结果表明，有必要在粉尘模型中纳入更真实的粉尘颗粒尺寸和 RI，以便更好地估计粉尘 DRE，特别是在粉尘源附近，并且主要用于研究粉尘气溶胶的局部辐射效应。