Aerosol complex refractive index (ACRI) is a key micro-physical parameter used for modeling their radiative effects. In this study, an approach is developed to estimate the ACRI using a combination of surface-based measurements (2008–2015) from the Aerodynamic Particle Sizer (APS), the integrating nephelometer, and the aethalometer over a tropical rural location in the southern peninsular India. Around 98% of the real part of the estimated ACRI varied in the range of 1.3–1.8 while 99% of the imaginary part was found to vary in the range of 0.01–0.2 at 550 nm. The estimated imaginary parts are found to be high during pre-monsoon season suggesting the dominance of the increased absorption type aerosols. This is in line with the high concentration of black carbon aerosol observed during the pre-monsoon. The spectral variation of estimated ACRI is also studied and finally the significance of refractive index of surface aerosols in columnar properties is analysed by using the columnar single scattering albedo (SSA) and aerosol optical depth (AOD) observations from sky radiometer. During winter season, the contribution to the total columnar scattering and absorption are mainly from surface or below the atmospheric boundary layer aerosols, whereas in monsoon season 80–90% contribution is from aerosols above.

气溶胶复合折射率（ACRI）是用于模拟辐射效应的关键微物理参数。在这项研究中，研究人员开发了一种方法，通过结合使用空气动力学粒径仪（APS）的基于表面的测量值（2008-2015），浊度计和浊度仪，对南部半岛南部的热带农村地区进行估算印度。估计的ACRI的约98％的实部在1.3–1.8范围内变化，而在550 nm处，虚部的99％在0.01–0.2范围内变化。在季风前季节，估计的假想部分很高，表明吸收型气溶胶的增加占主导地位。这与在季风爆发前观测到的高浓度的黑碳气溶胶相吻合。还研究了估计的ACRI的光谱变化，最后通过使用天空辐射计观察到的柱状单散射反照率（SSA）和气溶胶光学深度（AOD）来分析表面气溶胶的折射率在柱状性质中的重要性。在冬季，对总柱状散射和吸收的贡献主要来自地表或大气边界层以下的气溶胶，而在季风季节，80-90％的贡献来自上方的气溶胶。