Elfouhaily T., D.R.
Thompson, B. Chapron, D. Vandemark, 2001: Improved electromagnetic
bias theory: Inclusion of hydrodynamic modulations, JOURNAL OF
GEOPHYSICAL RESEARCH-OCEANS, 106 (C3),
4655-4664.
Sea level rise with time and variation
about the globe is measured using satellite radar altimeters such as
TOPEX/POSEIDON. The present study addresses improvements in one of the
critical geophysical corrections applied to the radar sea level estimates.
The correction is called the electromagnetic bias and it is an
altimeter-specific term to compensate for that fact that the radar's
probing pulse reflects off a wave-covered, moving sea surface rather than
a flat well-understood reflector. Sea level rise is occurring at a rate
of 1 to 2 mm/year. The EM bias correction presently carries an
uncertainty of 3-4 cm - the largest within the altimeter's error budget.
While averaging the long-term signals does lower this error source's
importance, improvement in its estimate is desired.
This paper is one in a series of three describing a model for the ocean
surface and the altimeter's reflection from it. The model must depict the
ocean surface in sufficient detail to go beyond the typical assumption of
a smoothly varying wave-like (or linear) surface. The non-linearity
needed in the surface wave model is the key focus of this paper. The
basis comes from the classic idea that the long ocean wave heave acts on
shorter ocean waves to modify the entire surface wave description.
Results show that our new incorporation of long and short wave
interactions leads to revised estimates of the altimeter electromagnetic
bias. Model results are now being used to instruct the possible
combination of altimeter and operational ocean wave model data, where the
wave model data will be used as an additional input to improve the
operational sea level estimate.
