This study is an attempt to estimate the radiative characteristics of aerosols, namely, the scattering coefficient (β_sc), absorption coefficient (β_ab), extinction coefficient (β_ex), single scattering albedo (ω) and the phase function P(θ), on a seasonal basis, incorporating the concurrent measurements of aerosol mass loading, size distribution and chemical composition at the tropical coastal site, Thiruvananthapuram. The software package Optical Properties of Aerosols and Clouds (OPAC) has been made use for the estimation of the radiative parameters. This paper presents the seasonal features of aerosol chemical composition and their source characteristics also. Along with this, the association between size-resolved number density of aerosols and their chemical characteristics were also investigated through correlation analysis. The location is significantly influenced by human activities as seen from the dominance of the anthropogenic component which is highest in winter (22%) with comparable values in pre-monsoon and post-monsoon and minimum in monsoon (13%). The sea-salt contribution is found to peak in monsoon (~40%) and attain a minimum in winter. The source characterization using principal component analysis along with back-trajectory analysis showed the seasonally changing mixed aerosol sources over the region. Accordingly, the radiative properties of aerosols also exhibit significant seasonal variations. β_sc varied from 0.04 to 0.14 km⁻¹ and β_ab between 0.01 and 0.05 km⁻¹ over a year. The single-scattering albedo exhibited significant seasonal differences being ~0.71 for winter and ~0.89 (0.55 μm) for monsoon season, indicating the presence of more absorbing aerosols in winter.

中文翻译：

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热带地区近地表气溶胶的辐射特性：基于同时测量其理化特性的估算

这项研究是估计的气溶胶，即散射系数（的辐射特性的尝试β _SC），吸收系数（β _AB），消光系数（β_前），单散射反照率（ω）和相位函数P（θ），并在季节性基础上结合了热带沿海站点提卢湾安塔普兰（Thiruvananthapuram）的气溶胶质量负荷，尺寸分布和化学成分的同步测量。气溶胶和云的光学特性（OPAC）软件包已用于估算辐射参数。本文介绍了气溶胶化学成分的季节特征及其来源特征。此外，还通过相关分析研究了气溶胶的尺寸分辨数密度与其化学特性之间的关联。从人为因素的主导地位来看，该位置受到人类活动的显着影响，该因素在冬季最高（22％），在季风前和季风后具有可比性，而在季风时最低（13％）。发现海盐贡献在季风时达到峰值（约40％），而在冬季达到最低。使用主成分分析和后向轨迹分析进行的源表征显示了该地区季节性变化的混合气溶胶源。因此，气溶胶的辐射特性也表现出明显的季节性变化。β _SC变化从0.04到0.14公里^-1和β _AB 0.01之间和0.05公里^-1超过一年。单散射反照率表现出明显的季节差异，冬季约为0.71，季风季节约为0.89（0.55μm），表明冬季存在更多的吸收气溶胶。