Intraseasonal Oscillations of the Indian Monsoon Rainfall during 1901-2010

Abstract:

The intraseasonal oscillations (ISOs) of the summer monsoon rainfall over India during 1901-2010 are examined. The ISOs are extracted by applying a data-adaptive method on the high-resolution gridded daily rainfall. Two leading ISOs emerge as nonlinear oscillations with broad-band spectra centered at 45 and 30 days. Both the ISOs propagate northward. The first ISO also propagates eastward while the second ISO shows some westward propagation. The amplitude of the first ISO is usually higher than that of the second ISO. This study examines whether there are modulations of the ISOs on interannual and decadal time scales and whether there are secular trends. The variability of the amplitude, variance and period of the ISOs during 1901-2010 is also investigated.