Radio Refractive Index over India and Their Climatic Classification for Microwave Propagation

Abstract

The climatology of refractivity has assumed great importance due to large increase in the use of many kinds of microwave radar and communication systems. The refractivity of the air on the surface (Ns) computed from the pressure, temperature and humidity over 230 stations in India and also from over neighbouring countries and adjacent seas has been studied in this paper. Since refractivity at the surface varies with height, and cannot therefore be used to draw isogonals, the most suitable factor to reduce these values to the sea level has been obtained from the mean radiosonde data of 12 stations over India.The charts showing the surface refractivity (03 GMT) and their values reduced to sea level have been drawn for January and it is shown that with the former the isogonals followed the contour of the land, while it is very much simplified when reduced to sea level. Charts have been drawn for each month of the year showing the sea level refractivity, as also the annual mean, the highest and the lowest mon...