GLOBAL STRUCTURE OF THE MADDEN-JULIAN OSCILLATIONS DURING 2 RECENT CONTRASTING SUMMER MONSOON SEASONS OVER INDIA

The global nature of the Madden-Julian Oscillations (MJOs) have been i nvestigated by applying a frequency filter to daily data for the summe r monsoon months (June to September) during two contrasting years - 19 87, a deficient monsoon year and 1988, an excess monsoon year. Several meteorological parameters at five levels in the troposphere have been examined. Regions with large amplitude of these oscillations are isol ated for each year. The results indicate that the global spatial distr ibution of these oscillations is more in a deficient year than in an e xcess year, in particular over the Indian subcontinent and the EI Nino Southern Oscillation (ENSO) regions. The principal modes of variabili ty during these two years have been investigated through Empirical Ort hogonal Functions (EOFs). The first two eigenmodes of 850 hPa zonal wi nd explain nearly 50% of the variance. The dipole type of structure be tween the Indian and the Pacific region is more apparent in 1987 than in 1988. Time-longitude cross sections of the filtered zonal wind over the equatorial regions clearly show that eastward propagation is dete cted in 1987, but is virtually absent in 1988. It is also seen that th e 30-60 day filtered winds are stronger during the monsoon of 1987 tha n in 1988.