Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity

Anguelova, Magdalena D.; Gaiser, P.W.

doi:10.3390/rs4051162

Cited by 38 publications

(23 citation statements)

References 50 publications

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“…Another type of directional dependence occurs because the foam and capillary waves are not uniformly distributed over the underlying structure of large-scale waves. The dependence of foam and capillary waves on the underlying structure produces an upwind-downwind asymmetry in the ocean surface emissivity [13]. The anisotropy of capillary and small gravity waves is responsible for the observed dependence of radar backscattering on wind direction.…”

Section: Ocean Emission Modelmentioning

confidence: 99%

“…So, complicated objects at the ocean surface, named integrally as -foam‖, actually presents a mixture of foam, whitecaps, bubbles, spray, aerosol, and also water-biogenic and water-oil emulsions. All of these formations are modeled with serious difficulties because of their instability and microstructure variety [13,26]. Furthermore, the third roughness effect is the diffraction of the microwaves by surface waves, which are small compared to the radiation wavelength.…”

Section: Ocean Emission Modelmentioning

confidence: 99%

“…As a rule, general differences between various geophysical models concern either the way in which sea surface wind dependency of the ocean emission is taken into account or which of the several water vapor absorption model is used for the atmospheric radiance calculation [2,12]. For low microwave frequency range (L-band) adequate sea water permittivity model becomes also important for the accurate ocean radiance modeling [9,13]. Restriction of the model by non-precipitating conditions is valid for the frequencies less than 37 GHz for clear and cloudy atmosphere and for light rain up to ~2 mm/h [14].…”

Section: Introductionmentioning

confidence: 99%

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An Updated Geophysical Model for AMSR-E and SSMIS Brightness Temperature Simulations over Oceans

2014

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Abstract:In this study, we considered the geophysical model for microwave brightness temperature (BT) simulation for the Atmosphere-Ocean System under non-precipitating conditions. The model is presented as a combination of atmospheric absorption and ocean emission models. We validated this model for two satellite instruments-for Advanced Microwave Sounding Radiometer-Earth Observing System (AMSR-E) onboard Aqua satellite and for Special Sensor Microwave Imager/Sounder (SSMIS) onboard F16 satellite of Defense Meteorological Satellite Program (DMSP) series. We compared simulated BT values with satellite BT measurements for different combinations of various water vapor and oxygen absorption models and wind induced ocean emission models. A dataset of clear sky atmospheric and oceanic parameters, collocated in time and space with satellite measurements, was used for the comparison. We found the best model combination, providing the least root mean square error between calculations and measurements. A single combination of models ensured the best results for all considered radiometric channels. We also obtained the adjustments to simulated BT values, as averaged differences between the model simulations and satellite measurements. These adjustments can be used in any research based on modeling data for removing model/calibration inconsistencies. We demonstrated the application of the model by means of the development of the new algorithm for sea surface wind speed retrieval from AMSR-E data.

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Section: Ocean Emission Modelmentioning

confidence: 99%

Section: Ocean Emission Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Updated Geophysical Model for AMSR-E and SSMIS Brightness Temperature Simulations over Oceans

2014

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“…For the purpose of present work the formation time of whitecaps * is negligible [20], so the only parameter left is the decay time τ'.…”

Section: Methodsmentioning

confidence: 99%

Numerical Simulation of Whitecaps and Foam Effects on Satellite Altimeter Response

2014

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Abstract:The determination of wave height by active satellite remote sensing, be it Synthetic Aperture Radar (SAR) or altimeter, has been a common practice for many years and is now imbedded on many meteorological and oceanographic forecasting systems. Despite their differences, all active sensors are based on the measurement of the Normalized Radar Cross Section (NRCS) of the sea surface, i.e., of its backscattering properties, which in turn depend on the wind velocity. At small and moderate wind speeds, the main mechanism is the formation of ripples (small scale waves); at higher speeds, whitecaps appear, and foam starts playing an essential role in determining NRCS. In the past few years much research effort has gone into clarifying these effects, thus improving the general quality of the measurements. Little work, however, has been devoted so far to consider the vertical spatial variation of backscattering properties, and in particular of the floating foam, over the sea surface. As it is shown in the present paper, the shape of the backscattered electromagnetic impulse in radar altimeters depends on the spatial distribution of foam over the water height in the sea waves and therefore the performance of these instruments in determining Significant Wave Height (H s ) and Sea Surface Level (SSL) is strongly affected by this effect. This work tackles these problems by making use of specially implemented numerical algorithms to simulate both sea surface processes and radar altimeter techniques. Results show that some causes of errors can be better understood and eventually corrected: in particular, the paper deals with the reconstruction of the electromagnetic Sea State Bias (SSB), the well known altimeter ranging error due to the presence of ocean waves on the sea surface.

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“…The high emissivity of sea foam increases the emissivity of the ocean (Anguelova and Gaiser, 2012) when W > 0.…”

Section: Measurements Of Sea Surface Brightness Temperaturementioning

confidence: 99%

On direct passive microwave remote sensing of sea spray aerosol production

et al. 2014

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Abstract. This study addresses and attempts to mitigate persistent uncertainty and scatter among existing approaches for determining the rate of sea spray aerosol production by breaking waves in the open ocean. The new approach proposed here utilizes passive microwave emissions from the ocean surface, which are known to be sensitive to surface roughness and foam. Direct, simultaneous, and collocated measurements of the aerosol production and microwave emissions were collected aboard the FLoating Instrument Platform (FLIP) in deep water ∼ 150 km off the coast of California over a period of ∼ 4 days. Vertical profiles of coarse-mode aerosol (0.25-23.5 µm) concentrations were measured with a forward-scattering spectrometer and converted to surface flux using dry deposition and vertical gradient methods. Back-trajectory analysis of eastern North Pacific meteorology verified the clean marine origin of the sampled air mass over at least 5 days prior to measurements. Vertical and horizontal polarization surface brightness temperature were measured with a microwave radiometer at 10.7 GHz frequency. Data analysis revealed a strong sensitivity of the brightness temperature polarization difference to the rate of aerosol production. An existing model of microwave emission from the ocean surface was used to determine the empirical relationship and to attribute its underlying physical basis to microwave emissions from surface roughness and foam within active and passive phases of breaking waves. A possibility of and initial steps towards satellite retrievals of the sea spray aerosol production are briefly discussed in concluding remarks.

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Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity

Cited by 38 publications

References 50 publications

An Updated Geophysical Model for AMSR-E and SSMIS Brightness Temperature Simulations over Oceans

An Updated Geophysical Model for AMSR-E and SSMIS Brightness Temperature Simulations over Oceans

Numerical Simulation of Whitecaps and Foam Effects on Satellite Altimeter Response

On direct passive microwave remote sensing of sea spray aerosol production

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