Editor’s note: For easy download the posted pdf of the State of the Climate for 2017 is a low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
Abstract. In this paper we investigate the underlying dynamics associated with a strong, line-shaped submesoscale feature that was observed in radar imagery at the boundary between Gulf Stream (GS) and shelf water near Cape Hatteras during the first Naval Research Laboratory High-Resolution Remote Sensing Experiment (HIRES 1). The lineshaped feature, which appears as a pronounced (---10 dB) increase in radar cross section, extends several kilometers in the east-west direction. In situ current measurements have shown that this feature coincides with the boundary of a sharp current convergence front. These measurements also indicate that the frontal dynamics is associated with the subduction of denser GS water under lighter shelf water. Using the observation that the convergence can be attributed to a hydrodynamic instability at the water interface, we have modeled the resulting subsurface hydrodynamics on the basis of a rigid-lid, twodimensional solution of the Navier Stokes equation. The calculations of subsurface current flow were used as input to a spectral (wave action) model of wave-current interaction to obtain the surface wave field, which in turn was used to provide input for modeling of radar backscatter. The resulting description also includes the effects of surfactant-induced wave damping on electromagnetic backscatter. Our predictions are compared with real aperture radar imagery and in situ measurements from the HIRES 1 experiment. IntroductionThe ability to infer the underlying current and depth structure from microwave frequency radar imagery of the ocean surface is a long-standing problem of considerable interest. Efforts to infer subsurface structure are inherently limited since radar signals at best penetrate the subsurface at the level of tens of centimeters or less. As a consequence, in the absence of ground truth, it is possible to understand subsurface structure in this manner only on the basis of some understanding and modeling of the underlying dynamics. On the other hand, interpretation of features apparent in ocean imagery is possible only if the link between radar modulation and variations in the small-scale surface roughness due to currents, depth, wind, and the associated momentum fluxes is correctly described. Further complicating the problem, especially at low wind speed, is the effect of wave damping from surfactants. A complete analysis of this problem is manifold, involving subsurface and surface hydrodynamics and electromagnetic backscatter. shown that this signature occurs along the boundary of a sharp current convergence front. These measurements also indicate that the frontal dynamics is associated with the subduction of denser Gulf Stream (GS) water under lighter shelf water. The goal of this paper is to marry subsurface current flow, surface wave-current interaction, and radar imaging, on the basis of a full-spectral representation, to obtain an understanding of this high radar backscatter feature, which will be referred to as a current "rip." As shown in Plate 1, the resul...
Editors note: For easy download the posted pdf of the State of the Climate for 2014 is a very low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download.
The relationship between personal prayer and perceived purpose in life is explored among two samples of twelve-to-fifteen-year-olds. The first sample comprises 914 males and 726 females who never attend church. The second sample comprises 232 males and 437 females who attend church most weeks. The data demonstrate a significant positive relationship between frequency of personal prayer and perceived purpose in life among both groups.
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