Radio Meteorology Variation of Radio Refractive Index with Height in the Lower Troposphere in India

ABSTRACTA study of surface refractivity Ns and the decrease of refractivity in the first kilometre ΔN, for six typical Indian stations is reported. Possible seasonal and diurnal variations of the effective earth radius factors, and the tropospheric trans-horizon signal strengths are discussed. A high degree of correlation is observed between the total refractivity N and the water vapour term Nw. No significant correlation is observed between Ns and ΔN except a weak correlation in the evening hours, a result which forbids the use of Ns and an exponential reference atmosphere for prediction of trans-horizon signal strengths in the Indian (tropical) climatic conditions.