Remotely sensed features in the US JGOFS Arabian Sea Process Study

TOPEX/POSEIDON altimeter data and wind data are used to calculate the geostrophic transport and Ekman transport in the northern Arabian Sea within the upper 500 m. In the summer, the upper 500-m layer in the northern Arabian Sea is horizontally divergent, with a transport going out of the northern Arabian Sea across 15.75°N reaching a maximum of 10×106 m3 s−1 in late June. In the winter, it is horizontally convergent, with a transport within the upper 500 m layer across 15.75°N reaching about 5×106 m3 s−1 into the northern Arabian Sea. The mean net transport for 1993–1995 out of the northern Arabian Sea across 15.75°N within the upper 500 m is estimated to be 0.74×106 m3 s−1. Most of the deep water upwelling across the 500 m depth, which compensates for the loss of waters in the upper 500-m layer, occurs in the eastern part of the northern Arabian Sea. The North Equatorial Current is found to deflect into the Arabian Sea during the NE Monsoon and the Spring Intermonsoon periods. In addition, estimates are made of the net transport into and out of the region encompassed by the US Joint Global Ocean Flux Study (JGOFS) Arabian Sea Process Study. The total transport out of the US JGOFS region is approximately 3.5–4.0×106 m3 s−1 in July of 1995 in the upper 500 m. Analysis of the mean sea surface height for the Arabian Sea shows a periodic change with the seasonal monsoon, with a typical depression of the ocean surface during the summer indicative of Arabian Sea cooling. The yearly change of the averaged sea surface height at 15.75°N is of the order of 15 cm. Rossby wave propagation also was observed at 15.75°N in the sea surface height fields.