Assimilation of altimeter data in a quasi-geostrophic model of the Gulf Stream system : a dynamical perspective
MetadataShow full item record
The dynamical aspects involved in the assimilation of altimeter data in a numerical ocean model have been investigated. The model used for this study is a quasi-geostrophic model of the Gulf Stream region. The data that have been assimilated are maps of sea surface height which have been obtained as the superposition of sea surface height variability deduced from the Geosat altimeter measurements and a mean field constructed from historical hydrographic data. The method used for assimilating the data is the nudging technique. Nudging has been implemented in such a way as to achieve a high degree of convergence of the surface model fields toward the observations. We have analyzed the mechanisms of the model adjustment, and the final statistical equilibrium characteristics of the model simulation when the surface data are assimilated. Since the surface data are the superposition of a mean component and an eddy component, in order to understand the relative role of these two components in determining the characteristics of the final st atistical steady state, we have considered two different experiments: in the first experiment only the climatological mean field is assimilated, while in the second experiment the total surface streamfunction field (mean + eddies) has been used. We have found that the mean component of the surface data determines, to a large extent, the structure of the flow field in the subsurface layers, while the eddy field, as well as the inflow/outflow conditions at the open boundaries, affect its intensity. In particular, if surface eddies are not assimilated only a weak flow develops in the two deeper model layers where no inflow/ outflow is prescribed at the boundaries. Comparisons of the assimilation results with available in situ observations show a considerable improvement in the degree of realism of the climatological model behavior, with respect to the model in which no data are assimilated. In particular, the possibility of building into the model more realistic eddy characteristics, through the assimilation of the surface eddy field, proves very successful in driving components of the mean model circulation that are in good agreement with the available observations.
Submitted 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 1993
Showing items related by title, author, creator and subject.
Understanding the ocean carbon and sulfur cycles in the context of a variable ocean : a study of anthropogenic carbon storage and dimethylsulfide production in the Atlantic Ocean Levine, Naomi M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2010-02)Anthropogenic activity is rapidly changing the global climate through the emission of carbon dioxide. Ocean carbon and sulfur cycles have the potential to impact global climate directly and through feedback loops. Numerical ...
Green, Rebecca E. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2002-06)Predictions of chlorophyll concentration from satellite ocean color are an indicator of phytoplankton primary productivity, with implications for foodweb structure, fisheries, and the global carbon cycle. Current models ...
Oceanic lithosphere magnetization : marine magnetic investigations of crustal accretion and tectonic processes in mid-ocean ridge environments Williams, Clare M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-09)The origin of symmetric alternating magnetic polarity stripes on the seafloor is investigated in two marine environments; along the ridge axis of the fast spreading East Pacific Rise (EPR) (9º 25’-9º 55’N) and at Kane ...