Applications of an Indian Ocean Observing System to Climate Impacts and Resource Predictions in Surrounding Countries in the Context of ENSO-Monsoon Teleconnections
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We explore the path between Indian Ocean observations and monsoon dynamics, the societal impacts of interannual climate variations and applications of resource predictions in southeastern Africa, the Mascarene Islands, India, southeast Asia and Australia. Recent progress in understanding ocean dynamics associated with SST variation is reviewed. The global El Niño-Southern Oscillation (ENSO) affects monsoon winds and ocean temperatures in a manner consistent with, but lagging, the Pacific. The ENSO influence often propagates across the tropical Indian Ocean from Africa to Indonesia, modulating the tropospheric moisture flux over the Indian Ocean and rainfall in surrounding continents. An east-west dipole in SST anomalies and monsoon rainfall is identified and related to the atmospheric Walker Cell. It appears partially in response to global ENSO conditions during build-up phase (July-Nov.). The eastern ‘node’ is confined near Sumatra, whilst the western centre of action extends from the Maldives to the Seychelles Islands. Correlations indicate that the strength of ENSO in the Indian Ocean region has decreased in recent decades, while large scale, spatial and temporal patterns suggest independent variations of the Indian Ocean. Apart from annual variations of the monsoon and year-to-year fluctuations of climate, short-term weather events have a dramatic impact on countries around the Indian Ocean. Recent floods in southern (2000) and eastern (1997- 98) Africa and southeast Asia (1998) are related to SST patterns and localised atmospheric responses. Predictions of the future availability of food and water resources, and short-term forecasts of storm events are some of the decision tools that can be offered through information from ocean data. The close relationship between regional SST anomalies and impacts on the food and water resources of surrounding countries provides a strong motivation for sustained observations in the Indian Ocean. A specific design plan for the observational network is proposed, linking eastern and western efforts in an efficient manner.
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