Radiometric observations before and during a rain event at a tropical location

At the University of Calcutta, Kolkata (22° 34´E, 88° 22´N) a humidity and temperature profiler (RPG-HATPRO) along with an optical rain gauge are utilized to study various meterological parameters (namely, integrated water vapour content, relative humidity, absolute humidity, liquid water path and atmospheric attenuation) prior to and during a rain event. Results indicate that water vapour actually starts increasing followed by an increase in liquid water content as well as in absolute humidity profile preceding the rain. The multi-frequency attenuation values, as obtained from the radiometric observations, also exhibit the impact of the changes in the atmospheric parameters due to pre-raining situations. A primary increase in atmospheric attenuation at 7 different frequency ranging of 22.24-31.40 GHz due to excess water vapour injection prior to rain is found to be followed by an enhanced attenuation caused by rain. A consequent change in pattern of variation multi-frequency attenuation is also detected indicating the relative impacts of water vapour and rain attenuation at different raining conditions.