In-situ measurements of atmospheric aerosols by using Integrating Nephelometer over a semi-arid station, southern India

摘要

Continuous real-time measurements of aerosol scattering properties were investigated at Anantapur (14 62' N, 77° 65' E, 331 m asl), a semi-arid region in southern India for the period of January 2011-December 2011, using a three-wavelength Integrating Nephelometer. Aerosols scattering properties like the scattering coefficient (σ_(sp)), backscattering coefficient (σ_(bsp)), scattering Angstrom exponent (A), backscat-tering ratio (b_λ) and asymmetry parameter (g_λ) were measured for the period of study. The average values of (±standard deviation) σ_(sp), σ_(bsp) at 550 nm (σ_(sp)~(550), σ_(bsp)~(550))and A_((700/450)) were found to be 97 (±9.2) M m~(-1) and 14 (±0.93) M m~(-1) and 1.02 (±0.3), respectively. The estimated average values of b_λ and g_λ at 550 nm from σ_(sp)~(550) and σ_(bsp)~(550) were 0.13 (±0.09) and 0.59 (±0.1), respectively. The maximum asymmetry parameter at 550 nm was found to be 0.63 ± 0.01 in the month of October and minimum (0.52 ± 0.03) during March, which shows the opposite trend with backscattering ratio. Significant correlation coefficients were noticed between different aerosol optical properties. The highest values of σ_(sp)~(550) were observed during weekdays whereas low values during weekends. Scattering Angstrom exponent for the summer and winter seasons has been consistent with the input of fine mode particles from anthropogenic origin.