Air-Sea Interaction at Contrasting Sites in the Eastern Tropical Pacific: Mesoscale Variability and Atmospheric Convection at 10°N

J. Thomas Farrar, Ph.D., 2007
Robert Weller, Advisor

The role of ocean dynamics in driving air-sea interaction is examined at two contrasting sites on 125ºW in the eastern tropical Pacific Ocean using satellite data and data from two air-sea interaction moorings. Analysis reveals marked differences in the role of ocean dynamics in modulating sea surface temperature (SST). At a near-equatorial site (3ºS), the 1997-1998 El Nino event dominated the evolution of SST and surface heat fluxes, and it is found that wind-driven southward Ekman transport was important in the local transition from El Nino to La Nina conditions. At a 10ºN site near the summertime position of the Inter-tropical Convergence Zone, oceanic mesoscale motions played an important role in modulating SST at intraseasonal (50- to 100-day) timescales. The characteristics and possible generation mechanisms of this mesoscale variability are examined. Focusing on 10ºN in the eastern tropical Pacific, the hypothesis that mesoscale oceanic SST variability can systematically influence cloud properties is investigated using several satellite data products. A statistically significant relationship between SST and columnar cloud liquid water and surface solar radiation is identified within the wavenumber-frequency band corresponding to oceanic Rossby waves.