Among others, ENSO (El Nino/ Southern Oscillation), a conspicuous phenomenon resulting from air-sea interaction in the tropical Pacific, exerts enormous influence upon climatic variability and weather abnormality on a decadal scale. It is our urgent task to clarify the mechanism of the phenomenon. In order to understand water circulation and heat transports in the ocean, we need to collect the data on currents, temperature, and salinity in the upper ocean over a long range of time. A buoy network is expected to play a vitally important role in achieving the following objectives.
2.2 Variability in the upper layer of the tropical Pacific and its adjacent seas in relation to ENSO and Asian monsoon
The TOGA (Tropical Ocean Global Atmosphere) programme from 1985 to 1994 has revealed that the ENSO phenomena causes dramatic changes in water temperature, salinity, and circulation in the surface-layer of the Equatorial Pacific. It has also shown that such changes gives rise to abnormal weather in mid-latitudes, as well as in the tropics. Specific processes and conditions, however, leading to the ENSO's occurrence have yet to be understood. Neither have we obtained scientific ability to make reliable forecasts. An important first step to the understanding of the ENSO mechanism is to undertake study of the process of the growth and dissipation of the warm pool in the western Pacific, an area where the water temperature goes up to the world highest acting as an engine driving the atmosphere. We must also study the variability in low-latitude western-boundary currents such as the New Guinea Coastal and the Mindanao Currents. Other topics that should be surveyed include the relationship between the ENSO and the Asian monsoon climate in the Indian Ocean. Heat and salt exchange between the Pacific and the Indian Ocean by the Indo-Pacific Throughflow must also be studied to understand the global ocean circulation.
2.3 Decadal scale variability in the upper and middle depth layers in mid- and high-latitude seas
The mid- and high-latitude seas are where heat from the subtropical gyre is transferred to the subpolar gyre, and where the intermediate water layer is formed with the fresh-water fed sea water subducting due to wintertime cooling. Measuring the surface fluxes, water temperature, and salinity in those seas is very useful to study the water mass formation and long-range climate variation on a decadal scale. It is also important to study the relationship between variabilities in the tropical Pacific like ENSO and that in the subtropical gyre including the Kuroshio and the Kuroshio Extension.
