Publications

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2017
Villas Bôas, AB, Gille ST, Mazloff MR, Cornuelle BD.  2017.  Characterization of the deep-water surface wave variability in the California current region. Journal of Geophysical Research: Oceans.   10.1002/2017JC013280   Abstract

Surface waves are crucial for the dynamics of the upper ocean not only because they mediate exchanges of momentum, heat, energy, and gases between the ocean and the atmosphere, but also because they determine the sea state. The surface wave field in a given region is set by the combination of local and remote forcing. The present work characterizes the seasonal variability of the deep–water surface wave field in the California Current region, as retrieved from over two decades of satellite altimetry data combined with wave buoys and wave model hindcast (WaveWatch III). In particular, the extent to which the local wind modulates the variability of the significant wave height, peak period, and peak direction is assessed. During spring/summer, regional–scale wind events of up to 10 m/s are the dominant forcing for waves off the California coast, leading to relatively short period waves (8-10 s) that come predominantly from the north–northwest. The wave climatology throughout the California Current region shows average significant wave heights exceeding 2 m during most of the year, which may have implications for the planning and retrieval methods of the Surface Water and Ocean Topography (SWOT) satellite mission.

2014
Mazloff, MR, Gille ST, Cornuelle B.  2014.  Improving the geoid: Combining altimetry and mean dynamic topography in the California coastal ocean. Geophysical Research Letters. 41:8944-8952.   10.1002/2014gl062402   AbstractWebsite

Satellite gravity mapping missions, altimeters, and other platforms have allowed the Earth's geoid to be mapped over the ocean to a horizontal resolution of approximately 100km with an uncertainty of less than 10cm. At finer resolution this uncertainty increases to greater than 10cm. Achieving greater accuracy requires accurate estimates of the dynamic ocean topography (DOT). In this study two DOT estimates for the California Current System with uncertainties less than 10cm are used to solve for a geoid correction field. The derived field increases the consistency between the DOTs and along-track altimetric observations, suggesting it is a useful correction to the gravitational field. The correction is large compared to the dynamic ocean topography, with a magnitude of 15cm and significant structure, especially near the coast. The results are evidence that modern high-resolution dynamic ocean topography products can be used to improve estimates of the geoid.

1999
Worcester, PF, Cornuelle BD, Dzieciuch MA, Munk WH, Howe BM, Mercer JA, Spindel RC, Colosi JA, Metzger K, Birdsall TG, Baggeroer AB.  1999.  A test of basin-scale acoustic thermometry using a large-aperture vertical array at 3250-km range in the eastern North Pacific Ocean. Journal of the Acoustical Society of America. 105:3185-3201.   10.1121/1.424649   AbstractWebsite

Broadband acoustic signals were transmitted during November 1994 from a 75-Hz source suspended near the depth of the sound-channel axis to a 700-m long vertical receiving array approximately 3250 km distant in the eastern North Pacific Ocean. The early part of the arrival pattern consists of raylike wave fronts that are resolvable, identifiable, and stable. The later part of the arrival pattern does not contain identifiable raylike arrivals, due to scattering from internal-wave-induced sound-speed fluctuations. The observed ray travel times differ from ray predictions based on the sound-speed field constructed using nearly concurrent temperature and salinity measurements by more than a priori variability estimates, suggesting that the equation used to compute sound speed requires refinement. The range-averaged ocean sound speed can be determined with an uncertainty of about 0.05 m/s from the observed ray travel times together with the time at which the near-axial acoustic reception ends, used as a surrogate for the group delay of adiabatic mode 1. The change in temperature over six days can be estimated with an uncertainty of about 0.006 degrees C. The sensitivity of the travel times to ocean variability is concentrated near the ocean surface and at the corresponding conjugate depths, because all of the resolved ray arrivals have upper turning depths within a few hundred meters of the surface. (C) 1999 Acoustical Society of America. [S0001-4966(99)04506-3].