Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Ocean Modelling 35 (2010): 119-133, doi:10.1016/j.ocemod.2010.08.003.
Four-dimensional Variational data assimilation (4DVAR) in the Regional Ocean
Modeling System (ROMS) is used to produce a best-estimate analysis of ocean
circulation in the New York Bight during spring 2006 by assimilating observations
collected by a variety of instruments during an intensive field program. An incremental
approach is applied in an overlapped cycling system with 3-day data assimilation window
to adjust model initial conditions. The model-observation mismatch for all observed
variables is reduced substantially. Comparisons between model forecast and independent
observations show improved forecast skill for about 15 days for temperature and salinity,
and 2 to 3 days for velocity. Tests assimilating only certain subsets of the data indicate
that assimilating satellite sea surface temperature improves the forecast of surface and
subsurface temperature but worsens the salinity forecast. Assimilating in situ
temperature and salinity from gliders improves the salinity forecast but has little effect on
temperature. Assimilating HF-radar surface current data improves the velocity forecast
by 1-2 days yet worsens the forecast of subsurface temperature. During some time
periods the convergence for velocity is poor as a result of the data assimilation system
being unable to reduce errors in the applied winds because surface forcing is not among
the control variables. This study demonstrates the capability of 4DVAR data assimilation
system to reduce model-observation mismatch and improve forecasts in the coastal ocean,
and highlights the value of accurate meteorological forcing.
This work was funded by National Science Foundation grant OCE-0238957.
New York Bight
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