Park, C.-K. and S. Schubert, 1995: Interannual and subseasonal variations of the summer monsoon during the ENSO cycle (GSFC/GEOS). Abstracts of the First International AMIP Scientific Conference, Monterey, California, 67.

The prediction of monsoon rainfall is a challenging task in the modeling community because of the complexities associated with the thermal and mechanical effects of high mountain terrain and the land/sea contrast interacting with the seasonal cycle. While the monsoon evolution is largely phase-locked with the seasonal cycle, the interannual variations of the intensity and arrival of the monsoon are yet to be understood. The Data Assimilation Office (DAO) in the Goddard Space Flight Center/NASA has recently produced a five-year global analysis employing a fixed assimilation system. The Goddard Earth Observing System (GEOS) analysis dataset is used to evaluate the GEOS GCM simulation of the contrasting dynamical and thermodynamical characteristics of the Indian summer monsoon during the extreme monsoon years.

The years 1986/87 were characterized by a major El Niño event which was followed by a strong La Niña in 1988 characterized by cold SST anomalies in the tropical eastern Pacific. An apparent coupling between El Niño-Southern Oscillation (ENSO) and the monsoons manifested itself during these years by a drought in 1987 and flood in 1988 over the Indian summer monsoon region. The possible connection of the ENSO with the abnormal drought/flood conditions in the Asian summer monsoon region is examined in the GEOS analyses and the simulation. The impact of lower boundary forcing both on the subseasonal monsoon evolution and the low-frequency tropical oscillations is examined for two contrasting Pacific basin-wide warm/cold episodes. The characteristics of the barotropic energy conversion during these two extreme monsoon periods are of interest. This study will identify the different characteristics of low-frequency wave propagation associated with the excursion of heat sources in the course of the monsoon evolution.