SODAR ECHOES AND LINE OF SIGHT MICROWAVE PROPAGATION.

THE VERTICALLY SOUNDING MONOSTATIC SODAR OPERATING AT THE NATIONAL PHYSICAL LABORATORY FOR THE PAST FEW YEARS HAS BEEN PROVIDING MICROMETEOROLOGICAL INFORMATION OF THE THERMAL STRUCTURE OF THE BOUNDARY LAYER ESPECIALLY THE HEIGHT AND WIDTHOF THE LAYERING STRUCTURE FORMED UNDER STABLE CONDITIONS, HEIGHT OF THE ACTIVE CONVECTIVE STRUCTURE UNDER UNSTABLE CONDITIONS, PRESENCE OF UNDULATIONS (TURBULENT STRUCTURE FORMED UNDER STABLE CONDITIONS) AND HEIGHT OF THE TURBULENCE. THE PRESENCE OF THESE THERMAL STRUCTURES HAS BEEN STUDIED WITH RESPECT TO THE SIMULTANEOUS EXISTENCE OF THE MICROWAVE PROPAGATION FEATURES FOR A LINE OF SIGHT PATH WITH A RECEIVING END AT DELHI, INDIA. THE MICROWAVE COMMUNICATION CHARACTERISTICSHAVE BEEN FOUND TO HAVE A CORRESPONDENCE WITH THE SODAR STRUCTURES OF THE STABLE AND UNSTABLE BOUNDARY LAYER, THE STABLE BOUNDARY LAYER BEING RESPONSIBLE FOR MOST OF THE OBSERVED MICROWAVE FADING CHARACTERISTICS. A CORRELATION OF THE NATURE OF THE SODAR STRUCTURES HAS ALSO BEEN ESTABLISHED WITH THEMAGNITUDE OF THE INITIAL REFRACTIVITY GRADIENT PRESENT. A RAY TRACING PROGRAM HAS BEEN DEVELOPED TO DETERMINE THE TRAJECTORIES FOR THE LINE OF SIGHT LINK UNDER INVESTIGATION AND MODEL CALCULATIONS OF THE RECEIVED FIELD STRENGTH FOR SOME SELECTED VALUES OF INITIAL REFRACTIVITY GRADIENT HAVE BEEN GIVEN.