Modelling of the vertical radio refractivity near Arabian Sea

Properties of the propagation medium are of crucial importance in modelling the radio communication path. The refractivity of atmosphere decreases with ascending height; enabling beyond-horizon radio communication. Due to different climates in various regions around the globe, no universal equation can be formulated for calculation of atmospheric refractivity at varying altitudes. This paper presents a series of equations for calculation of annual and seasonal atmospheric refractivities, for Karachi city of Pakistan. The equations compute the refractivity at a given height Nh with reference to the ground or surface refractivity Ns. The equations are derived from one year recorded atmospheric data i.e. 2010 to 2011 and are in the general form of Nh=Nse-k, where k is the derived factor and accounts for the heights variations. This work is vital for scenarios when local meteorological data is not available for vertical profiling of atmosphere.