Amongst the suspended particles in the atmosphere, water vapor and fog are the most influencing parameters when microwave propagates through the atmosphere. Attenuation due to these along with rain are considered in detail, over Kolkata (22 0 N), India and Cachoeira Paulista (22 0 S), Brazil. Rain, perhaps is considered to be the worst offender in microwave propagation. The rain patterns over Kolkata, Brazil and U.K are compared and hence the attenuation also.

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The vertical attenuation rates (dB km Õ 1 ) due to the water vapour monomer model in the atmosphere at 22.235 GHz were estimated. The height distribution of meteorological parameters such as atmospheric pressure, temperature, water vapour pressure and water vapour densities along with attenuation rate were found to be best ® tted exponentially, except for the temperature distribution. Thus, the seasonal variation of estimated attenuation and the brightness temperatures were compared with the experimentally obtained radiometric observations at 22.235 GHz. Correlations between the estimated and observed values were studied. Then, by using the absorption data, water vapour scale height was determined. For this purpose, the inversion algorithm has been developed and results were in agreement with the estimated values. The water vapour scale height over Calcutta varied between 2.0 and 2.5 km.