![]() An optical sensor can detect water wave slopes generated by arbitrarily short water waves up to the wavelength of reflected light, while microwave radar can only measure a part of the surface slopes up to the radar wavelength. Their derived values are much higher than the observations of Cox and Munk (1954a, b), and much higher than the values required in (8). The MSS has also been derived from the ocean surface spectra ( Donelan and Pierson 1987 Apel 1994). (1992) is equal to our MSS for k up to 100 rad m −1. The comparison shows (not included in this paper) that the derived MSS by Jackson (1991) and Jackson et al. In their papers, the MSS contributed by the shorter waves is regarded as small structure and their effect on radar backscatter is included in the effective reflection coefficient, due to their special mathematical approach. ![]() (1992) used their derived MSS to determine the Phillips constant in the equilibrium range. (1992) is the part contributed by gravity waves. The eddy viscosity is due to turbulence at the wind-drift layer, which suppresses the spectrum of high-frequency waves with wavelengths on the order of millimeters. The parasitic capillary wave dissipation due to molecular viscosity can be balanced by the energy supply from the underlying waves, hence it is removed from the model. It is suggested that the k p/ k dependence observed in the range of gravity waves should not be extended to the region of short waves. This effect can be denoted by c 2/ U 2 10 or c 2/ c 2 p dependence of short-wave spectrum. The short-wave dissipation due to wave–drift interactions has the effect of suppressing the spectral density at high wind condition, which further influences the directional spreading rate. The physics included in this model on gravity–capillary wave spectrum is also illustrated. Also, the RBCS, calculated using the C-band filtered MSS, is in keeping with the ERS-1/-2 scatterometer empirically based algorithms CMOD3 and CMOD4. The radar backscatter cross section (RBCS), calculated from specular reflection theory using the Ku-band filtered MSS, is in keeping with the empirically based Ku-band models by Brown for the GEOS-3 13.9-GHz altimeter, and by Witter and Chelton for the Geosat 13.5-GHz altimeter. The MSS integrated from the above two spectra over high-frequency dissipation length (1 mm) fits the optical observations very well. Every year thousands of people are rescued by coastguards and lifeguards along the West and East Coasts of the United States, while approximately 100 people lose their lives.The mean-square slope (MSS) of the sea surface for upwind and crosswind is derived, based on Phillips’ equilibrium spectrum and the model herein on gravity–capillary wave spectrum. Panicked swimmers counter rip currents by trying to swim back to the shore but risk drowning due to fatigue. The current drag swimmers and small boats further into the ocean. Rip currents are narrow channels of powerful fast-moving water prevalent along the coast. Are Cross Seas and Rip Currents Similar?Ĭross waves differ from rip currents. They are relatively rare and can appear and disappear within a matter of minutes. They pull surfers and swimmers far into the ocean while rocking boats and ships from all directions. ![]() Generally, cross waves are impressive to look at, but in the real sense, they are extremely dangerous even in small swells. Cross waves are not permanent, they lose energy as they travel, and the local winds can also interfere, causing the square pattern to fade away. Visitors are advised to stay out of the ocean during the waves. They are common at the Isle of Rhe in France where they attract a significant number of tourists. Square waves can occur in any part of the ocean as long as the conditions are right. Cross waves are more dangerous than riptides as the square pattern makes it difficult to navigate. ![]() Above the surface, the waves appear gentle, but what lurks beneath are currents strong enough to wreck ships. When waves traveling in different directions collide they create the square pattern of the cross sea. Without the presence of the local winds to disrupt the swells, they travel over vast distances. Waves travel for hundreds of miles over the sea surface, and even on a calm day, storms raging far in the ocean can create rolling waves known as swells. The distinguishing feature is that the angles are occasionally greater than 45°. Square waves are caused by two different sets of waves converging at different angles. The waves appear gentle on the surface, but they are strong enough to steer swimmers, surfers, boats, and even large ships into unintended courses. Square waves, also known as cross sea or cross waves, are square-shaped grids that form on the surface of the ocean. What Causes Square Waves In The Ocean? A cross sea is caused by two sets of waves converging at different angles. ![]()
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