Microwave Specular Measurements and Ocean Surface Wave Properties

Microwave reflectometers provide spectrally integrated information of ocean surface waves several times longer than the incident electromagnetic (EM) wavelengths. For high wind condition, it is necessary to consider the modification of relative permittivity by air in foam and whitecaps produced by wave breaking. This paper describes the application of these considerations to microwave specular returns from the ocean surface. Measurements from Ku and Ka band altimeters and L band reflectometers are used for illustration. The modeling yields a straightforward integration of a closed-form expression connecting the observed specular normalized radar cross section (NRCS) to the surface wave statistical and geometric properties. It remains a challenge to acquire sufficient number of high-wind collocated and simultaneous reference measurements for algorithm development or validation and verification effort. Solutions from accurate forward computation can supplement the sparse high wind databases. Modeled specular NRCSs are provided for L, C, X, Ku, and Ka bands with wind speeds up to 99 m/s.

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Modeling Microseism Generation by Inhomogeneous Ocean Surface Waves in Hurricane Bonnie Using the Non-Linear Wave Equation

Remote Sensing ◽

10.3390/rs10101624 ◽

2018 ◽

Vol 10 (10) ◽

pp. 1624

Author(s):

Joshua Wilson

Keyword(s):

Wave Equation ◽

Surface Wave ◽

Surface Waves ◽

Ocean Surface ◽

Linear Wave ◽

Linear Wave Equation ◽

Ocean Surface Waves ◽

Non Linear ◽

Hurricane Bonnie ◽

Ocean Surface Wave

It has been shown that hurricanes generate seismic noise, called microseisms, through the creation and non-linear interaction of ocean surface waves. Here we model microseisms generated by the spatially inhomogeneous waves of a hurricane using the non-linear wave equation where a second-order acoustic field is created by first-order ocean surface wave motion. We treat range-dependent waveguide environments to account for microseisms that propagate from the deep ocean to a receiver on land. We compare estimates based on the ocean surface wave field measured in hurricane Bonnie in 1998 with seismic measurements made roughly 1000 km away in Florida.

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First Observations of Microbaroms with Single Absolute Barometers

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2011jtecha1526.1 ◽

2011 ◽

Vol 28 (7) ◽

pp. 933-943 ◽

Cited By ~ 3

Author(s):

Ganesh K. Subramanian ◽

Andreas Muschinski

Keyword(s):

Surface Wave ◽

Atlantic Ocean ◽

Surface Waves ◽

Frequency Spectrum ◽

Ocean Surface ◽

Upper Atmosphere ◽

Ocean Surface Waves ◽

Equilibrium Spectrum ◽

Ocean Surface Wave ◽

First Time

Abstract The first observations of microbaroms with single absolute barometers are presented and discussed. Microbaroms are pulses of atmospheric infrasound emitted by ocean surface waves. They can propagate over thousands of kilometers through the atmosphere, and they can reach altitudes well into the upper atmosphere before they are refracted down to the earth’s surface. Typical microbarom periods are 5 s, typical wavelengths are 1.5 km, and typical surface amplitudes are 100 mPa (1 μbar). The data presented here were collected during the 2-week period from 26 February through 10 March 2008 in Amherst, Massachusetts, which is located about 150 km away from the Atlantic Ocean. The authors report for the first time, to the best of their knowledge, an f−5 microbarom frequency spectrum, which is consistent with Phillips’s f−5 ocean surface wave equilibrium spectrum.

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