Sensing of radio refractivity and aerosol extinction

Sensing of radio refractivity has historically been accomplished with direct sensing techniques such as radiosondes. While direct sensing techniques provide good data for propagation assessment purposes, remotely sensed data would be more desirable. Various direct and remote sensing techniques and an assessment of their potential operational usefulness are reviewed. Included are radiosondes, refractometers, radar sounders, lidars, satellite-based sensors, radiometric and radio propagation techniques. The need for and feasibility of providing three-dimensional, time-varying refractivity fields for propagation assessment are addressed. Aerosol extinction is often the atmospheric parameter limiting electrooptical systems performance. For proper performance assessment, slant path extinction must be known. For several decades, attempts have been made to infer aerosol extinction from lidar backscatter measurements. A discussion of selected lidar techniques and their limitations is presented