Interactions between the Asian Monsoons, the Tropical Pacific, and the Southern Hemisphere Extratropics

摘要

Relatively strong and weak years of Indian monsoon rainfall are selected and used as a starting point to follow the evolution of the annual cycle of precipitation in the tropical Indian and Pacific sectors. Analysis of observations shows that the dynamically coupled ocean-atmosphere system in the Indian-Pacific region produces Southern Oscillation-type signals in atmosphere and ocean in many years, with extremes being manifested as Warm and Cold Events. The high southern latitudes in four general circulation model simulations show internally consistent circulation anomalies involving sensitivity to the annual cycle of sea surface temperatures at mid-latitudes and sea ice extent at high latitudes, both of which have an effect on the semiannual oscillation at those latitudes. The observed sequence of Warm minus Cold Event composites shows a poleward migration of anomalies with the troocs leading the high latitudes by about half a year.