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dc.contributor.authorFarrar, J. Thomas
dc.coverage.spatial10°N 125°W
dc.coverage.spatialTropical Pacific Ocean
dc.date.accessioned2007-04-13T15:12:48Z
dc.date.available2007-04-13T15:12:48Z
dc.date.issued2007-02
dc.identifier.urihttp://hdl.handle.net/1912/1567
dc.descriptionSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2007en
dc.description.abstractThe role of ocean dynamics in driving air-sea interaction is examined at two contrasting sites on 125°W in the eastern tropical Pacific Ocean using data from the Pan American Climate Study (PACS) field program. Analysis based on the PACS data set and satellite observations of sea surface temperature (SST) reveals marked differences in the role of ocean dynamics in modulating SST. At a near-equatorial site (3°S), 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 10°N 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, and the buoy observations suggest that there are variations in surface solar radiation coupled to these mesoscale SST variations. This suggests that the mesoscale oceanic variability may influence the occurrence of clouds. The intraseasonal variability in currents, sea surface height, and SST at the northern site is examined within the broader spatial and temporal context afforded by satellite data. The oscillations have zonal wavelengths of 550-1650 km and propagate westward in a manner consistent with the dispersion relation for first baroclinic mode, free Rossby waves in the presence of a mean westward flow. The hypothesis that the intraseasonal variability and its annual cycle are associated with baroclinic instability of the North Equatorial Current is supported by a spatio-temporal correlation between the amplitude of intraseasonal variability and the occurrence of westward zonal flows meeting an approximate necessary condition for baroclinic instability. Focusing on 10°N 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 (CLW), cloud reflectivity, and surface solar radiation is identified within the wavenumber-frequency band corresponding to oceanic Rossby waves. Analysis of seven years of CLW data and 20 years surface solar radiation data indicates that 10-20% of the variance of these cloud-related properties at intraseasonal periods and wavelengths on the order of 10° longitude can be ascribed to SST signals driven by oceanic Rossby waves.en
dc.description.sponsorshipI gratefully acknowledge support from the following sources: NOAA Grants NA87RJ0445 (2002-2003) and NA17RJ1223 (2005-2006), and an MIT Presidential Fellowship (2000-2001). I also received support from The Cooperative Institute for Climate and Ocean Research, a NOAA-WHOI joint institute (NOAA Grant NA17RJ1223).en
dc.format.mimetypeapplication/pdf
dc.language.isoen_USen
dc.publisherMassachusetts Institute of Technology and Woods Hole Oceanographic Institutionen
dc.relation.ispartofseriesWHOI Thesesen
dc.subjectOcean-atmosphere interactionen_US
dc.subjectCloud physicsen_US
dc.subjectRoger Revelle (Ship) Cruise Genesis 4en_US
dc.subjectThomas G. Thompson (Ship) Cruise TN73en_US
dc.subjectMelville (Ship) Cruise PACS03MVen_US
dc.titleAir-sea interaction at contrasting sites in the eastern tropical Pacific : mesoscale variability and atmospheric convection at 10°Nen
dc.typeThesisen
dc.identifier.doi10.1575/1912/1567


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