Estimates of water vapour absorption over Calcutta at 22.235 GHz
The vertical attenuation rates (dB km-1) due to the water vapour monomer model in the atmosphere at 22.235GHz 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 fitted 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 22.235GHz. 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 2.5km.