ON THE EXTRACTION OF NEAR-SURFACE INDEX OF REFRACTION USING RADAR PHASE MEASUREMENTS FROM GROUND TARGETS

The speed al which electromagnetic waves travel between a radar and a target is dependent on the index of refraction of the atmosphere betwe en the radar and the target. Modern radars can have sufficiently accur ate time bases and digitizing equipment observe small changes in the t ime it rakes a radar signal to travel to a Bred target and back. These changes are related to small perturbations in the refractive index ca used by changes in humidity, temperature, and pressure. Using the phas e information from ground targets and its time evolution as a proxy fo r the changes in travel time of radar waves, a procedure for measuring the near-surface index of the refraction field around the radar is de monstrated and implemented on the McGill Doppler S-band radar. This pa per describes the theory behind the measurement, and a technique used to extract refractive index data from ground targets. Early measuremen ts of the index of refraction field are also presented, and some of th e possibilities offered by this new radar-measured variable are identi fied.