Newsletter No.7 July-1999@

  As you know,ocean continuously supplies large amount of moisture to the atmosphere and drives the global hydrologic cycle.Because of its large heat capacity,ocean can serve as a huge reservoir of heat energy,thereby slowing down the pace of global warming.Ocean and the atmosphere exchange not only heat and moisture but also momentum,and generate large-scale variation of climate such as Southern Oscillation.It was late 1960s when Kirk Bryan and I developed a relatively simple,coupled ocean-atmosphere-land surface model,combining a general circulation of the atmosphere with that of oceans.Despite its simplicity,the coupled model was very useful for the elucidation of the role of ocean and land surface in determining the large-scale distribution of climate.

  During the last 30 years,coupled models have been used increasingly for the studies of both global warming and natural,unforced variation of climate.These studies are motivated by success in simulating not only the broad scale feature of climate but also its natural variabilities.For example,a coupled model approximately reproduces the observed temporal variabilities of both local and global-mean surface temperatures.It also reproduces reasonably well the fluctuation of sea surface temperature (SST)induced by Southern Oscillation of decadal as well as interannual time scales.A coupled model has been shown to produce so-called North Atlantic Oscillation (NAO),multidecadal variability of the North Atlantic thermohaline circulation with associated SST change,and the decadal SST variation in the tropical Atlantic.It is also very encouraging that coupled models have some skill for predicting Southern Oscillation/El Nino event in the tropical Pacific Ocean.Although concern has been expressed on various shortcomings of currently available coupled models,they have become very powerful tools for the study of climate.

  I am very pleased that staff members at the Institute for Global Change Research/FRSGC have recently embarked on the development of a coupled ocean-atmosphere-land surface model through close collaboration across various subprograms. With the installation of very fast computer towards the end of this year and the availability of extremely powerful "Earth Simulator"in less than three years,we look forward to exploring the physical mechanisms responsible for natural and anthropogenic changes of climate and assessing their predictability.



Coupled Ocean-Atmosphere-Land Model


- 3 -