Abstract
Present analysis emphasises on the change in the vertical profiles of relative humidity (RH) with the progress of Indain summer monsoon during 2009, 2010 and 2011. The study is carried out with the onset of monsoon over Kerala and its progress in Mumbai and Delhi. Relative humidity profiles are obtained using NOAA/ERSL radiosonde observations and Global Positioning System Radio Occultation (GPSRO),Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC) derived 1-DVAR temperature, pressure and water vapour pressure profiles. High relative humidity between 5 and 7 Km is observed one day before onset over the above mentioned stations. Whereas, on onset day, a significant dip in RH at the similar altitude can be considered as a signature for monsoon onset.
