Diurnal Cycle of Air-Sea Interactions in Frontal Regions

Meghan F Cronin, NOAA Pacific Marine Environmental Laboratory, Seattle, WA, United States and Dongxiao Zhang, CICOES/University of Washington and NOAA/PMEL, Seattle, WA, United States
In regions of high insolation and low winds, diurnal warming of the ocean surface can lead to an increase in sea surface temperature (SST) of several degrees Celsius, and a temperature stratification that extends through the top few meters of the ocean. There is growing understanding that resolving this diurnal warming is necessary for numerical coupled atmosphere-ocean systems. In this presentation, we use observations from Saildrone, a new, wind- and solar-powered autonomous surface vehicle measuring high frequency air-sea fluxes and upper ocean currents, to show how diurnal warming is affected by SST fronts in the eastern tropical Pacific. In particular, we show how fronts that lead to destabilization of the atmospheric boundary layer, lead to increased surface winds and ocean turbulence, which reduces the amplitude of the SST diurnal cycle. Implications about frontal air-sea interaction and the need of Tropical Pacific Observing System to resolve fronts and high frequency variability will be discussed.