Determination of Moisture Changes Prior to the Onset of South-West Monsoon Over Kerala Using NOAA/TOVS Satellite Data

The temperature and moisture data from TIROS operational vertical sounder (TOVS) are examined to obtain humidity parameters like, mid and upper tropospheric water vapour, and scale height of water vapour. Their usefulness in characterizing the onset of south-west (SW) monsoon over India is studied. The NOAA satellite data (finished product) with a resolution of 2.5 ~ lat/lon are used to obtain these parameters during and prior to the SW monsoon season over selected regions during 1979 to 1985. The pentad averaged values in the western Indian Ocean showed an increase in scale height of water vapour and mid-tropospheric moisture (700-500 rob) over about 8 to 10 days prior to the onset over Kerala coast. The association of the moisture flux across the Indian Ocean and the rainfall over Kerala coast has also been examined. Results showed that the gradient of middle level moisture is stronger in the case of rainfall deficit years.