Estimates of sea surface height and near-surface alongshore coastal currents from combinations of altimeters and tide gauges

SARACENO, M., P. T. STRUB, AND P. M. KOSRO

JOURNAL OF GEOPHYSICAL RESEARCH

Año: 2008 p. 1 - 20

0148-0227

Present methods used to retrieve altimeter data do not provide reliable estimates ofsea surface height (SSH) in the nearshore region, resulting in a measurement gap of25–50 km next to the coast. In the present work, gridded SSH fields produced byArchiving, Validation, and Interpretation of Satellite Oceanographic data (AVISO) in theoffshore region are combined with coastal tide gauge time series of SSH to improveestimation in that gap along the west coast of the United States in the northern CaliforniaCurrent System between 40
and 45
N and 123.8
and 126
W. To assess the increasein skill provided by this procedure, the geostrophic alongshore currents, calculated fromthe new SSH fields in the gap region, are compared to three in situ, nearshore currentmeasurements, resulting in correlation coefficients of 0.73–0.83 and standard deviationsof the differences of 11.6–12.6 cm/s, substantially improved from the AVISO-only results.When the Ekman current components are estimated and added to the geostrophiccurrents, comparisons to the 10 m deep acoustic Doppler current profiler velocities areonly slightly improved. The Ekman components make a more significant contributionwhen compared to HF radar surface current measurements, providing correlations of0.94 and standard deviations of the differences of 6.4–9.5 cm/s. These results represent adramatic improvement in the quality of the SSH fields and estimated alongshorecurrents when additional, realistic SSH data from the coastal region are added.Here we use coastal tide gauges to provide the additional SSH data but also discuss moregeneral approaches for altimeter SSH retrievals in coastal regions where tidegauge data are not available.