Application of satellite-derived OLR data in the prediction of the onset of Indian summer monsoon

Outgoing Longwave Radiation (OLR) data, obtained from NOAA polar orbiting satellites for the months March–June, for 31 years is utilized to investigate low-frequency oscillation in pre-monsoon convection over southwest peninsular Indian region. The analysis reveals a characteristic fall in OLR over the region, about 5–9 weeks prior to the onset of Indian summer monsoon in almost all the years under study. Such fall is shown to be related with a characteristic peak in convective activity associated with the movement of Inter-Tropical Convergence Zone over the region. The results suggest an indirect non-linear relationship between the time of occurrence of the pre-monsoon convective peak and the onset date. A regression equation is developed to predict the onset date. The results of estimation of present method and that of an earlier method (based on conventional synoptic observations) are compared. The performance of both these methods is validated for two independent years (2007 and 2008). The study highlights the potential application of the developed method for the prediction of onset of Indian summer monsoon well in advance using the remotely sensed satellite-derived OLR data.