Acoustic sounder applications: remote sensing of sea breeze and radio propagation studies over tropical India

Acoustic sounding is one of the remote sensing techniques that can give continuous information about some of the micro-meteorological parameters of the lower atmosphere. Microwave propagation is strongly influenced by the atmospheric boundary layer where radioclimatological phenomena such as temperature inversions, fronts, and thunderstorms cause steep refractivity gradients. An important parameter in the study of tropospheric propagation is the refractive index which causes reflection, refraction, diffraction and scattering of radio waves. In an effort to identify the causes of fading over LOS microwave links a monostatic sodar was installed at Tirupati (receiving end of the links) to probe the dynamic behavior of lower atmospheric effects on LOS propagation. The observational study has provided some basic understanding of the boundary layer characteristics affecting propagation and benefitted the development of a climatological model. The authors present some observed significant episodes pertinent to the classification of fading characteristics associated with each of the various atmospheric conditions. In addition, possibilities for the causes of fading are also discussed. It is concluded that severe fading in the early morning and late evening hours is caused due to temperature inversions observed over this region