Effective medium approximation model of sea foam layer microwave emissivity of a vertical profile

Wei, En-Bo

doi:10.1080/01431161.2012.718461

Cited by 17 publications

(11 citation statements)

References 39 publications

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“…Unstable atmospheric conditions enhance the generation and the thickness and coverage of foam and whitecaps. Although the phenomenon of increases in observed radiances under unstable conditions has been studied (Monahan and O'Muircheartaigh, 1986;Reul and Chapron, 2003;Shibata, 2003Shibata, , 2007Wei, 2013), no emissivity model is yet available that includes the effect of atmospheric stability on foam coverage.…”

Section: Biases In Cold Sectorsmentioning

confidence: 99%

Effects of all‐sky assimilation of GCOM‐W/AMSR2 radiances in the ECMWF numerical weather prediction system

Kazumori

Geer

English

2015

Quart J Royal Meteoro Soc

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This article assesses the impact of Advanced Microwave Scanning Radiometer 2 (AMSR2) radiances in the all‐sky assimilation of the European Centre for Medium‐Range Weather Forecasts (ECMWF). Individual impacts of three microwave imagers including AMSR2 were examined by using a baseline experiment that had no microwave imager data. The three microwave imagers brought similar improvements in humidity, temperature and wind first‐guess (FG) fields in the troposphere. Improvements were found in fits to both analyses and other observations. Moreover, significant improvements in wind and geopotential height fields in the troposphere were found in day 3–6 forecasts. AMSR2 made larger improvements than other microwave imagers to geopotential height forecasts in the Northern Hemisphere. The use of AMSR2 radiance data in addition to the other existing microwave imagers gave mixed results. Consistent improvements in the FG fit to humidity observations were confirmed. However, the FG fit for several channels of the microwave temperature sounding instruments was degraded. The mean FG departure of AMSR2 showed biases that varied according to the time of day and meteorological conditions. The causes of the biases were identified as insufficient representation of the cloud liquid water path (LWP) in the forecast model under unstable conditions and insufficient amplitude of LWP diurnal variation in stratocumulus areas in the Tropics. The assimilation of too much biased data might start to bring negative effects for the analyses and forecasts, which for some parameters could outweigh the improvements in the assimilation. However, despite this, AMSR2 brought significant improvements of the geopotential height field in the Southern Hemisphere lower troposphere for day 5–7 forecasts.

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Section: Biases In Cold Sectorsmentioning

confidence: 99%

Effects of all‐sky assimilation of GCOM‐W/AMSR2 radiances in the ECMWF numerical weather prediction system

Kazumori

Geer

English

2015

Quart J Royal Meteoro Soc

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“…To adequately account for foam effects on brightness temperature or emissivity, one needs to understand the microwave electromagnetic properties of a foam layer, such as permittivity and emissivity. In fact, these two complex properties are not only related to foam microstructure parameters such as air volume fraction (AVF), foam layer thickness and size of seawater-coated air bubbles, but also microwave frequency, SST and SSS [5][6][7][8][9][10][11]. Although the sea foam layer can increase sea surface emissivity [12], this mechanism is not clearly understood, especially in calculating or predicting emissivity and permittivity of that layer.…”

Section: Introductionmentioning

confidence: 99%

“…To disclose the effects of other foam parameters, such as the ratio of coated air bubbles' inner to outer radii, coherent wave interaction, and sticky force parameter on foam emissivities, microwave radiative transfer theory has also been applied to the foam layer [7,9,22,23]. For the AVF with vertical distribution in a foam layer, Wei [10] proposed an EMA method to estimate foam emissivity of a non-uniform AVF. Similarly, Anguelova et al [5] and Raizer [21] presented a radiative transfer model for estimating the emissivity of a vertically structured foam layer at microwave frequencies.…”

Section: Introductionmentioning

confidence: 99%

“…Anguelova [3] systematically investigated well-known effective permittivity formulae of composite media according their applicability to the sea foam layer. To investigate the emissivity increment induced by a foam-covered sea surface, theoretical models [8][9][10][11][16][17][18][19][20][21] were developed with electromagnetic wave theory, microwave vector radiative transfer equation (VRTE), and EMA theory. For instance, Guo et al [17] investigated the influence of foam microstructures, microwave frequency and foam-layer thickness on the emissivity of a foam-covered sea surface with quasi-crystalline approximation and VRTE, by treating the foam as densely packed air bubbles coated with seawater.…”

Section: Introductionmentioning

confidence: 99%

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Emissivity Measurements of Foam-Covered Water Surface at L-Band for Low Water Temperatures

et al. 2014

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For a foam-covered sea surface, it is difficult to retrieve sea surface salinity (SSS) with L-band brightness temperature (1.4 GHz) because of the effect of a foam layer with wind speeds stronger than 7 m/s, especially at low sea surface temperature (SST). With foam-controlled experiments, emissivities of a foam-covered water surface at low SST (−1.4 °C to 1.7 °C) are measured for varying SSS, foam thickness, incidence angle, and polarization. Furthermore, a theoretical model of emissivity is introduced by combining wave approach theory with the effective medium approximation method. 10914 the foam layer emissivity increments are discussed for frequencies between 1 and 37 GHz.

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“…New models for the emissivity of vertically stratified foam layers have been published since our survey of foam emissivity modeling (Anguelova & Gaiser, ). The models of Wei () and Plant and Irisov () are notable for their different approach to accounting for the foam vertical variations. Thus, these models are good for independent comparison with our model (further discussed in section ).…”

Section: Modelsmentioning

confidence: 99%

Whitecap Fraction From Satellite Measurements: Algorithm Description

Anguelova

Bettenhausen

2019

JGR Oceans

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Many air‐sea interaction processes are quantified in terms of whitecap fraction W because whitecaps are the most visible and direct way of observing breaking waves with air entrainment in the open ocean. Photographs or video images of the sea state collected from towers, ships, and aircrafts have been used over the years to obtain W. Satellite remote sensing of W is a recent development that allows long‐term, consistent observations of whitecapping on a global scale. The method for estimating W uses the variations of ocean surface emissivity at microwave frequencies (6 to 37 GHz) due to presence of sea foam on a rough sea surface. Satellite‐borne microwave radiometers detect these variations at the ocean surface as changes of the brightness temperature TB at the top of the atmosphere. We present the physical and parameterized models, as well as the input data, necessary to calculate W from WindSat TB observations with our W (TB) algorithm. We describe the implementation versions through which the W (TB) algorithm has developed. We show that satellite‐based W data vary with the frequency and polarization of the TB observations. The wind speed dependence of the W retrievals at horizontal and vertical polarizations shows different behavior and compares differently with in situ W data and existing wind speed parameterizations W(U10). We discuss the applicability of our methodology to other radiometric data. We indicate possible modifications and tuning of the models in the W (TB) algorithm that can help to further improve the accuracy of the satellite W retrievals.

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Effective medium approximation model of sea foam layer microwave emissivity of a vertical profile

Cited by 17 publications

References 39 publications

Effects of all‐sky assimilation of GCOM‐W/AMSR2 radiances in the ECMWF numerical weather prediction system

Effects of all‐sky assimilation of GCOM‐W/AMSR2 radiances in the ECMWF numerical weather prediction system

Emissivity Measurements of Foam-Covered Water Surface at L-Band for Low Water Temperatures

Whitecap Fraction From Satellite Measurements: Algorithm Description

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