AN INSTABILITY THEORY OF AIR-SEA INTERACTION FOR COASTAL UPWELLING

A surface wind (seabreeze), thermally generated by differential sea surface temperature, is introduced to Gill-Clarke’s model (1974) through wind stress for investigating the effects of seabreeze on coastal upwel-ling. A coupled air-sea system is treated as an eigenvalue problem. The solutions show that the thermally forced local winds break down the coastal Kelvin wave into three parts: small-scale (L<100 km) growing and stationary modes, mesoscale (100 km<L<200 km) decaying and fast-moving modes, and ’large’-scale (L>200 km) coastal Kelvin modes. The consistency of the length scale between the most growing mode predicted by this model and the observed cold/warm alternation pattern of surface water near the Peruvian Coast (around 15 °S) implies that seabreeze may play some role in coastal upwelling.