Leben, R. R., Colorado Center for Astrodynam, Boulder, Colorado, USA, leben@colorado.edu
Hamlington, B. D., Colorado Center for Astrodynamics Research, University of Colorado, Boulder, Colorado, USA, benjamin.hamlington@colorado.edu
Powell, B. S., Institute of Marine Sciences, University of California, Santa Cruz, California, USA, powellb@ucsc.edu

OPTIMAL FILTERS FOR ESTIMATING SLOPE AND HIGHER-ORDER DERIVATIVES FROM ALONG-TRACK AND WIDE-SWATH ALTIMETRY

The rate of change or slope of the sea surface height from along-track altimetry is used to derive surface geostrophic currents; however, differentiation has high-pass characteristics that cause undesirable noise amplification. To mitigate the noise-enhancement effect on the accuracy of altimeter-derived velocities, along-track filtering is often applied to reduce the measurement noise and then the slope is estimated by a difference operation. Although these types of ad hoc methods have been successfully used for mesoscale studies, they do not optimally attenuate the white noise measurement error nor fully exploit the spatial resolution of the altimeter measurements. Optimal filters that combine filtering and differentiation can be derived that minimize the white noise signal while retaining second-order accurate approximation of the derivative on compact sampling stencils or grids. We show 1-D and 2-D versions of this class of optimal filters for estimating slope and higher order derivatives from along-track and wide-swath altimetry. Application of optimal filters to along-track and simulated wide-swath altimetry will be presented to highlight the efficacy of these filters for the altimetric study of velocity and vorticity fields.

Oral presentation

Presentation is given by student: No
Session #:006
Date: 03-05-2008
Time: 14:15