Prediction of transmission loss over transhorizon tropospheric propagation paths in the Indian subcontinent

A method for predicting transmission loss for transhorizon tropospheric radio paths, based on radio propagation and radio-meteorological observations over a number of transhorizon paths in five different regions of the Indian subcontinent, is described. The prediction depends upon correlation of field strength with the initial gradient of refractivity and an empirical relationship of this parameter with the Eklund-Wickert analytical model (1968). A method for accounting for the effect of superrefraction during high gradient conditions is discussed, and the statistical distribution of field strength is shown to be predictable from the statistical distribution of the initial refractivity gradient.