浙江大学毕磊研究员利用原地测量的粒径分布和较大粒径颗粒的影响对海盐气溶胶进行光学模拟，2024年3月8日出版的《大气科学进展》杂志发表了其最新的研究成果。

在这项研究中，研究人员分析了原地测量的海盐气溶胶粒径分布，使用多模态对数正态粒径分布来拟合数据。研究采用了超球体和包覆超球体来解释颗粒在潮解和结晶过程中的非球性、不均匀性和滞后效应。为了计算海盐气溶胶的单次散射特性，研究人员采用了最先进的不变量嵌入T矩阵方法，该方法可以在532nm波长下获得最大体积等效直径(Dp)为12μm的海盐气溶胶的精确光学特性。研究结果表明，在本研究中建立的颗粒模型，在不同相对湿度(RH)水平下成功地复制了测量的去偏极和激光雷达比率。

重要的是，研究观察到大粒径颗粒(Dp>4μm)对海盐气溶胶的光学性质有很大的影响，这在以前的研究中没有考虑到。具体来说，在ACE-Asia现场试验中，排除直径大于4μm的颗粒会导致散射系数和后向散射系数分别被低估27%-38%和43%-60%。此外，在50%-70%RH范围内，去偏极比被低估了0.15。研究结果强调了在海盐气溶胶的光学模拟中考虑大颗粒粒径的必要性。

据研究人员介绍，海盐气溶胶通过与太阳辐射的相互作用，在调节全球气候方面发挥着关键作用。这些颗粒的粒径分布是决定其整体光学性质的关键。

附：英文原文

Title: Optical modeling of sea salt aerosols using in situ measured size distributions and the impact of larger size particles

Author: Wushao Lin, Lei Bi

Issue&Volume: 2024-03-08

Abstract: Sea salt aerosols play a critical role in regulating the global climate through their interactions with solar radiation. The size distribution of these particles is crucial in determining their bulk optical properties. In this study, we analyzed in situ measured size distributions of sea salt aerosols from four field campaigns and used multi-mode lognormal size distributions to fit the data. We employed super-spheroids and coated super-spheroids to account for the particles’ non-sphericity, inhomogeneity, and hysteresis effect during the deliquescence and crystallization processes. To compute the single-scattering properties of sea salt aerosols, we used the state-of-the-art invariant imbedding T-matrix method, which allows us to obtain accurate optical properties for sea salt aerosols with a maximum volume-equivalent diameter (Dp) of 12 μm at a wavelength of 532 nm. Our results demonstrated that the particle models developed in this study were successful in replicating both the measured depolarization and lidar ratios at various relative humidity (RH) levels. Importantly, we observed that large size particles (Dp > 4 μm) had a substantial impact on the optical properties of sea salt aerosols, which has not been taken into account in previous studies. Specifically, excluding particles with diameters larger than 4 μm led to underestimations of the scattering and backscattering coefficients by 27% ~ 38% and 43% ~ 60%, respectively, for the ACE-Asia field campaign. Additionally, the depolarization ratios were underestimated by 0.15 within the 50%-70% RH range. These findings emphasize the necessity of considering large particle sizes for optical modeling of sea salt aerosols.

DOI: 10.1007/s00376-024-3351-3

Source: http://www.iapjournals.ac.cn/aas/en/article/doi/10.1007/s00376-024-3351-3viewType=HTML