Field Observations of Breaking of Dominant Surface Waves

The results of field observations of breaking of surface spectral peak waves, taken from an oceanographic research platform, are presented. Whitecaps generated by breaking surface waves were detected using video recordings of the sea surface, accompanied by co-located measurements of waves and wind velocity. Whitecaps were separated according to the speed of their movement, c, and then described in terms of spectral distributions of their areas and lengths over c. The contribution of dominant waves to the whitecap coverage varies with the wave age and attains more than 50% when seas are young. As found, the whitecap coverage and the total length of whitecaps generated by dominant waves exhibit strong dependence on the dominant wave steepness, ϵp, the former being proportional to ϵp6. This result supports a parameterization of the dissipation term, used in the WAM model. A semi-empirical model of the whitecap coverage, where contributions of breaking of dominant and equilibrium range waves are separated, is suggested.

High-alumina pyroxenite xenoliths from Quaternary basalts of NW Spitsbergen - evidence of continental crust delamination

The origin of spinel-garnet pyroxenite from xenoliths in Quaternary basaltoids of Spitsbergen Island (Svalbard Archipelago) is discussed. The rocks have a high concentration of Al2O3 and MgO and low Cr. The primary magmatic association Spl-Opx-Cpx and the high Al content in pyroxenes provide evidence for the formation of these rocks as cumulates of hydrous basaltic melts in the lower crust at a pressure of ~1.2 GPa. Transformation of the texture from the magmatic hypidiomorphic to the metamorphic granoblastic and growth of garnet at the expense of spinel and high-alumina pyroxenes indicate transport of rocks to a depth below the spinel/garnet phase transition boundary in the Cr2O3-free CaO-MgO-Al2O3-SiO2 system. The parameters of the Grt-Opx equilibrium range within 1060-1120 °C and 2.2-2.6 GPa. Thus, magmatic pyroxenite was transported to a great depth into the mantle, which provides evidence for delamination in the region of the lower continental crust containing ultramafic cumulates.

Inconsistent Spectral Evolution in Operational Wave Models due to Inaccurate Specification of Nonlinear Interactions

The introduction of third-generation (3G) models was based on the premise that wave spectra could evolve without prior shape restrictions only if the representation for nonlinear interactions contained as many degrees of freedom as the discretized spectrum being modeled. It is shown here that a different criterion is needed to accurately represent nonlinear spectral evolution within models, a more rigorous criterion such that the number of degrees of freedom in the nonlinear source term must be equal to the intrinsic number of degrees of freedom in the theoretical form of this source term, which is larger than the degrees of freedom in the spectrum. Evolution of spectral shapes produced by the current approximation for nonlinear interactions in 3G models, the discrete interaction approximation (DIA), is compared to the full integral solution for three different time scales: 1) relaxation of the equilibrium range following a perturbation, 2) spectral evolution of the equilibrium range during an interval of constant winds, and 3) the evolution of spectral shape during transition to swell during propagation over long distances. It is shown that the operational nonlinear source term produces significant deviations in the evolution of the wave spectra at all of these scales because of its parametric reduction of the number of degrees of freedom and incorrect energy flux scaling. It is concluded that the DIA does not meet the critical criterion for allowing a spectrum to evolve to spectral shapes consistent with those observed in nature.

Measurements of the Directional Spectrum across the Equilibrium Saturation Ranges of Wind-Generated Surface Waves

It is now well accepted that to better understand the coupling between the atmosphere and the ocean, and improve coupled ocean–atmosphere models, surface wave processes need to be taken into account. Here, properties of the directional distributions of the surface wave field across the equilibrium and saturation ranges are investigated from airborne lidar data collected during the ONR Southern California 2013 (SoCal2013) experiment, conducted off the coast of Southern California in November 2013. During the field effort, detailed characterization of the marine atmospheric boundary layer was performed from Research Platform (R/P) Floating Instrument Platform (FLIP), moored at the center of the aircraft operational domain. The wind speed ranged from approximately 1–2 to up to 11 m s−1, while the significant wave height varied from 0.8 to 2.5 m during the 10 days of data collection considered in the analysis. The directional wavenumber spectrum exhibits a clear, bimodal distribution that extends well beyond what was reported in previous studies, with the azimuthal separation between the lobes reaching ≈π for the highest wavenumbers that could be resolved: approximately 10–12 rad m−1. The results demonstrate that opposing wave components can be found in one storm system rather than requiring waves from opposing storms, with implications for ocean acoustics. With the broad wavenumber range of the directional spectra obtained from the lidar, the transition from the equilibrium to saturation ranges over a range of wind forcing conditions is found to occur for ≈ 1–2 × 10−3, where kn is the wavenumber at the upper limit of the equilibrium range, u* the friction velocity, and g the gravitational acceleration. The results are discussed in the context of Phillips’ model of the equilibrium range of wind-generated gravity waves.

International Real Estate Review

This paper examines the long-run equilibrium between real house prices and macroeconomic fundamentals in U.S. housing markets, as well as the short-run adjustment of real house prices back to the equilibrium. Pooled mean-group and mean-group estimation techniques developed by Pesaran and Smith (1995) and Pesaran et al. (1999) are applied to a panel of the 51 U.S. states over the period of 1976Q3 to 2012Q4. Our results suggest a common long-run relationship over the sample period between real house prices and their economic fundamental determinants in the 51 U.S. states. However, the speed of adjustment of real house prices varies vastly across states, with a half-life estimate of 22 quarters on average, and the deviations of real house prices from the equilibrium range from ¡V30% to 46% across states over time.

Wave Breaking Dissipation in a Young Wind Sea

Coupled in situ and remote sensing measurements of young, strongly forced wind waves are applied to assess the role of breaking in an evolving wave field. In situ measurements of turbulent energy dissipation from wave-following Surface Wave Instrument Float with Tracking (SWIFT) drifters and a tethered acoustic Doppler sonar system are consistent with wave evolution and wind input (as estimated using the radiative transfer equation). The Phillips breaking crest distribution Λ(c) is calculated using stabilized shipboard video recordings and the Fourier-based method of Thomson and Jessup, with minor modifications. The resulting Λ(c) are unimodal distributions centered around half of the phase speed of the dominant waves, consistent with several recent studies. Breaking rates from Λ(c) increase with slope, similar to in situ dissipation. However, comparison of the breaking rate estimates from the shipboard video recordings with the SWIFT video recordings show that the breaking rate is likely underestimated in the shipboard video when wave conditions are calmer and breaking crests are small. The breaking strength parameter b is calculated by comparison of the fifth moment of Λ(c) with the measured dissipation rates. Neglecting recordings with inconsistent breaking rates, the resulting b data do not display any clear trends and are in the range of other reported values. The Λ(c) distributions are compared with the Phillips equilibrium range prediction and previous laboratory and field studies, leading to the identification of several inconsistencies.