Monday 22 August 2005

P1

PM0058
Seasonality of atmospheric forcing and oceanic response over the warm pool prior to the 2002/2003 ENSO
Ando, Kentaro¹, Kuroda, Yoshifumi¹, Kutsuwada, Kunio2
1 IORGC/JAMSTEC, Japan
2 School of Marine Science and Technology, Tokai University, Japan
Author email: andouk@jamstec.go.jp
The surface current, temperature and wind data from TRITON array along 156E from 8N to 5S since 2000 has analyzed to clarify the seasonality of atmospheric forcing and its related oceanic responses. The zonal surface winds along the 156 ŠE indicates that the strong eastward wind forcing area shifts seasonally crossing the equator as its center located in the northern hemisphere during the boreal summer and in the southern hemisphere during the boreal winter in 2001 and in the early half of 2002. Due to the seasonal shifts, during the specific periods of intra-seasonal westerly wind forcing area crossing the equator, the surface winds induced effectively the strong eastward currents events. The satellite-derived wind field in the Pacific warm pool correlates well with the high sea surface temperature (SST) field provided by NOAA optical interpolation dataset, i.e. the westerly wind areas in seasonal mean are generally observed west of the high SST regions, which indicate the seasonality of large meridional shift. During boreal winter, the high SST region locates south of the equator, accompanying the westerly wind in the southern hemisphere. During spring to summer in 2001, the high SST regions indicate two peaks structure; one locates around 10N and 20N off-Philippine area and the other locates around the equator at the west of the first one. Associated with the distribution, the westerly wind area can be found from the south of first peak near off-Philippine area to the west of second peak near the equator. These results suggest that the air-sea interaction over the warm pool, associated with the seasonally meridional shift of high SST and wind fields and its related oceanic responses, may have the role to affect to the 2002/2003 El Nino onset.

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