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首页> 外文期刊>Atmospheric research >Investigating the size, shape and surface roughness dependence of polarization lidars with light-scattering computations on real mineral dust particles: Application to dust particles' external mixtures and dust mass concentration retrievals
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Investigating the size, shape and surface roughness dependence of polarization lidars with light-scattering computations on real mineral dust particles: Application to dust particles' external mixtures and dust mass concentration retrievals

机译：通过对真实矿物尘埃颗粒进行光散射计算来研究偏振激光雷达的尺寸，形状和表面粗糙度依赖性：在尘埃颗粒的外部混合物和尘埃质量浓度检索中的应用

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Our understanding of the contribution of mineral dust to the Earth's radiative budget is limited by the complexity of these particles, which present a wide range of sizes, are highly-irregularly shaped, and are present in the atmosphere in the form of particle mixtures. To address the spatial distribution of mineral dust and atmospheric dust mass concentrations, polarization lidars are nowadays frequently used, with partitioning algorithms allowing to discern the contribution of mineral dust in two or three-component particle external mixtures. In this paper, we investigate the dependence of the retrieved dust backscattering (beta(d)) vertical profiles with the dust particle size and shape. For that, new light-scattering numerical simulations are performed on real atmospheric mineral dust particles, having determined mineralogy (CAL, DOL, AGG, SIL), derived from stereogrammetry (stereo-particles), with potential surface roughness, which are compared to the widely-used spheroidal mathematical shape model. For each dust shape model (smooth stereo-particles, rough stereo-particles, spheroids), the dust depolarization, backscattering Angstrom exponent, lidar ratio are computed for two size distributions representative of mineral dust after long-range transport. As an output, two Saharan dust outbreaks involving mineral dust in two, then three-component particle mixtures are studied with Lyon (France) UV-VIS polarization lidar. If the dust size matters most, under certain circumstances, beta(d) can vary by approximately 67% when real dust stereo-particles are used instead of spheroids, corresponding to variations in the dust backscattering coefficient as large as 2 Mm(-1).sr(-1). Moreover, the influence of surface roughness in polarization lidar retrievals is for the first time discussed. Finally, dust mass-extinction conversion factors (eta(d)) are evaluated for each assigned shape model and dust mass concentrations are retrieved from polarization lidar measurements. From spheroids to stereo-particles, eta(d) increases by about 30%. We believe these results may be useful for our understanding of the spatial distribution of mineral dust contained in an aerosol external mixture and to better quantify dust mass concentrations from polarization lidar experiments.
机译：我们对矿物粉尘对地球辐射预算的贡献的理解受到这些粒子的复杂性的限制，这些粒子具有各种尺寸，高度不规则形状，并且以粒子混合物的形式存在于大气中。为了解决矿物粉尘的空间分布和大气粉尘质量浓度问题，当今经常使用极化激光雷达，其分配算法可以辨别矿物粉尘在两组分或三组分颗粒外部混合物中的作用。在本文中，我们研究了取回的粉尘后向散射（beta（d））垂直剖面与粉尘颗粒大小和形状的相关性。为此，对真实的大气矿物尘埃颗粒进行了新的光散射数值模拟，确定了由立体测量法（立体颗粒）得出的矿物学特征（CAL，DOL，AGG，SIL），并将其与潜在的表面粗糙度进行了比较。广泛使用的球形数学形状模型。对于每种粉尘形状模型（光滑的立体颗粒，粗糙的立体颗粒，球体），对于代表远距离运输后的矿物粉尘的两种尺寸分布，计算了粉尘去极化，反向散射埃斯特罗姆指数，激光雷达比。作为输出，使用里昂（法国）UV-VIS偏振激光雷达研究了两次撒哈拉沙漠爆发，其中两次将矿物粉尘混合，然后将三组分颗粒混合。如果粉尘的大小最重要，则在某些情况下，使用真实的粉尘立体粒子代替球体时，β（d）可能会发生约67％的变化，这相当于粉尘后向散射系数的变化高达2 Mm（-1） .sr（-1）。此外，首次讨论了极化激光雷达检索中表面粗糙度的影响。最后，针对每个分配的形状模型评估灰尘质量消光转换因子（eta（d）），并从极化激光雷达测量结果中获取灰尘质量浓度。从球状体到立体粒子，eta（d）大约增加30％。我们相信这些结果可能有助于我们理解气溶胶外部混合物中所含矿物粉尘的空间分布，并有助于通过极化激光雷达实验更好地量化粉尘质量浓度。

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