Session 3: Air-Sea Interaction in the Western Pacific (Chairs: P. Delecluse and T. Nakazawa)
In this session, we tried to understand the atmosphere-ocean interaction and variability over the western Pacific, including the South China Sea and the Indonesian Throughflow. There were 10 presentations for this scientific issue.
Drs. Delecluse, Hendon, Kitamura and Nakazawa discussed the ENSO mechanism over the Pacific Ocean. In particular, they focused on 1) the role of westerly wind bursts to the onset of the ENSO, 2) the intraseasonal air-sea interaction, and 3) the decadal variability. An important question raised during the talks was that whether the intraseasonal variation is really necessary for triggering the ENSO or not. To answer the question, we need further modeling study to improve the prediction/hindcast skill on interannual/annual/intraseasonal time-scale and the air-sea flux estimations. At the same time, we need to enhance the observational efforts and the data analyses on the fluctuation of the periodicity and clear/unclear organization/eastward movement of the MJO and a role of the MJO and the Indonesian convection/Australian monsoon activity for the onset of the ENSO. Dr. Noh showed a direction to advance the ocean model; he discussed the significant improvement of the SST prediction in OGCM by improving of mixed layer processes and the air-sea flux computations.
It was well recognized, by the presentation of Dr. Lukas, that it is very important to understand the dynamics of the annual change or the Asian-Australian monsoon system over the Indo-Pacific sector. He presented a scenario of the annual variation over the region by using several data sources, such as the ocean temperature, the sea level, and the surface wind and the rainfall data. Dr. Qu's presentation also showed us the importance of the air-sea interaction processes over the South China Sea.
There were very interesting presentations on the Indonesian throughflow. Dr. Molcard and Fieux showed the result from the current meters deployed in the Ombai Strait. The data shows a clear and distinct signal with a period of 30-60 days, which is the similar as the Madden-Julian Oscillation (MJO) in the tropical atmosphere. Dr. Masumoto et al. demonstrated the evolution of the eddy in the Sulawesi Sea in their ocean model and showed that this oscillation, of a period of about 40 days, is explained by the ocean dynamics, which is not related to the MJO fluctuation.
