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Statistics of optical turbulence from multi-year sonic anemometer-thermometer observations at a semi-arid region: effects of aerosols and atmospheric boundary layer dynamics

Accurate characterization of atmospheric refractive index fluctuations (optical turbulence) is important in applications such as Free-Space Optical (FSO) communication and laser remote sensing, where atmospheric optical propagation is involved. In this paper, we present the statistics of near-surface optical turbulence derived from three-year sonic anemometer-thermometer observations at a semi-arid, flat terrain in peninsular India. Using concurrent and collocated measurements of meteorological fields and atmospheric aerosols (both scattering and absorbing type), the role of atmospheric boundary layer dynamics and aerosols in modulating the magnitude, evolution, and temporal variations (over diurnal and seasonal scales) of refractive index structure parameter (Cn2) are discussed. Absorption of solar radiation and the resulting atmospheric heating by aerosol particles will modify the land-atmosphere temperature gradient that regulates the near-surface Cn2. We discuss such a scenario using aerosol black carbon measurements close to the surface of the Earth and highlight the crucial role of ABL dynamics in controlling the influence of such aerosol radiative heating effects on Cn2. These results will be helpful in improving the weather model simulations of optical turbulence over semi-arid regions.