Journal of Climate, 18(1), 5-25.
High-resolution satellite observations are used to investigate air-sea interaction over the eastern Pacific warm pool. In winter, strong wind jets develop over the Gulfs of Tehuantepec, Papagayo and Panama, accelerated by the pressure gradients between the Atlantic and Pacific across narrow passes of Central American cordillera. Patches of cold sea surface temperatures (SSTs) and high chlorophyll develop under these wind jets as a result of increased turbulent heat flux from the ocean and enhanced mixing across the bottom of the ocean mixed layer. Despite a large decrease in SST that exceeds 3°C in seasonal means, the cold patches associated with the Tehuantepec and Papagayo jets do not have an obvious effect on local atmospheric convection in winter since the intertropical convergence zone (ITCZ) is located further south. The cold patch of the Panama jet to the south, on the other hand, cuts through the winter ITCZ and breaks it into two parts.
A pronounced thermocline dome develops west of the Gulf of Papagayo, with the 20°C isotherm only 30m deep throughout the year. In summer when the Panama jet disappears and the other two wind jets weaken, SST is found to be 0.5°C lower over this Costa Rica Dome than the background. This cold spot reduces local precipitation by half, punching a hole of 500km in diameter in the summer ITCZ. The Dome underlies a patch of open-ocean high chlorophyll. This thermocline dome is an ocean dynamic response to the positive wind curls south of the Papagayo jet, which is optimally oriented to excite ocean Rossby waves that remotely affect the ocean to the west. The meridionally oriented Tehuantepec and Panama jets, by contrast, only influence the local thermocline depth with few remote effects on SST and the atmosphere. The orographical-triggered air-sea interaction described here is a good benchmark for testing high-resolution climate models now under development.
Dr. William S. Kessler
NOAA / PMEL / OCRD
7600 Sand Point Way NE
Seattle WA 98115 USA
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