3D complex refractivity using air quality and propagation models

Abstract

Electromagnetic radiation (EMR) propagation through atmosphere is a function of temperature, pressure and, composition. The composition of atmosphere will include natural and anthropogenic obscurants that alter radio refractive index. For the first time, we are using an air quality prediction model in retrospective mode for studying 3-dimensional complex refractive index profiles of the lower atmosphere from the surface up to the tropopause height. Since atmospheric obscurant concentration at any given geographic location and time, is dependent on history and dynamics of the air mass, and sources of emissions, it is important and realistic to consider a regional scale air quality model to infer time-varying 3 dimensional radio wave attenuation and seeing parameters. We will discuss methods to compute complex refractive index involving calculation of real and imaginary part of the refractive index which includes dispersion and total attenuation due to absorption and elastic scattering by gases, aerosols, and hydrometeors for the radio spectrum, and the free-space optical (FSO) propagation regime (20 THz to 375 THz). Our approach will adhere closely to past proven techniques, and following directions from most recent literature. For complex refractivity computation, we will proceed using scattering extinction efficiencies and also use the line-by-line absorption coefficient calculations using Van Vleck-Weisskopf shape functions and line-strengths for resonant, non-resonant and, continuum spectra as needed using Radiative Transfer Model (RTM).