Publication Date:
2022-05-25
Description:
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
Description:
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.
Description:
This research was carried out with the support of the National Aeronaut ics
Space Administration, through a contract to MIT from the Jet Propulsion
Laboratory, # 958208, as a part of the TOPEX-Poseidon investigation.
Keywords:
Ocean-atmosphere interaction
;
Ocean currents
;
Ocean temperature
Repository Name:
Woods Hole Open Access Server
Type:
Thesis
Format:
application/pdf
