The Experts below are selected from a list of 189 Experts worldwide ranked by ideXlab platform
Bertrand Chapron - One of the best experts on this subject based on the ideXlab platform.
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earth viewing l band radiometer sensing of sea surface scattered celestial Sky Radiation part i general characteristics
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Joseph Tenerelli, Nicolas Reul, Alexis Mouche, Bertrand ChapronAbstract:The ldquogalactic glitterrdquo phenomenon at L-band, i.e., the scattering of celestial Sky Radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident celestial brightness is uniform, sea surface roughness has a negligible impact on the glitter. At such a point, variations in both the orientation of the incidence plane and the wind direction relative to the scattering azimuth have negligible impact. By contrast, when the specular point lies in the vicinity of a localized maximum of brightness, scattering by the roughened ocean surface may reduce the glitter by more than 30%, as compared to a perfectly flat surface, and the glitter amplitude may vary by up to 0.7 K with variations in wind direction and by up to 0.5 K with variations in incidence plane orientation. It is shown that accounting for the roughness impact on celestial noise contamination is of particular concern for the remote sensing of SSS.
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earth viewing l band radiometer sensing of sea surface scattered celestial Sky Radiation part ii application to smos
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Nicolas Reul, Joseph Tenerelli, Nicolas Floury, Bertrand ChapronAbstract:We examine how the rough sea surface scattering of L-band celestial Sky Radiation might affect the measurements of the future European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. For this purpose, we combined data from several surveys to build a comprehensive all-Sky L-band celestial Sky brightness temperature map for the SMOS mission that includes the continuum Radiation and the hydrogen line emission rescaled for the SMOS bandwidth. We also constructed a separate map of strong and very localized sources that may exhibit L-band brightness temperatures exceeding 1000 K. Scattering by the roughened ocean surface of Radiation from even the strongest localized sources is found to reduce the contributions from these localized strong sources to negligible levels, and rough surface scattering solutions may be obtained with a map much coarser than the original continuum maps. In rough ocean surface conditions, the contribution of the scattered celestial noise to the reconstructed brightness temperatures is not significantly modified by the synthetic antenna weighting function, which makes integration over the synthetic beam unnecessary. The contamination of the reconstructed brightness temperatures by celestial noise exhibits a strong annual cycle with the largest contamination occurring in the descending swaths in September and October, when the specular projection of the field of view is aligned with the Galactic equator. Ocean surface roughness may alter the contamination by over 0.1 K in 30% of the SMOS measurements. Given this potentially large impact of surface roughness, an operational method is proposed to account for it in the SMOS level 2 sea surface salinity algorithm.
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Earth-Viewing L-Band Radiometer Sensing of Sea Surface Scattered Celestial Sky Radiation—Part I: General Characteristics
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Joseph Tenerelli, Nicolas Reul, Alexis Mouche, Bertrand ChapronAbstract:The ldquogalactic glitterrdquo phenomenon at L-band, i.e., the scattering of celestial Sky Radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident celestial brightness is uniform, sea surface roughness has a negligible impact on the glitter. At such a point, variations in both the orientation of the incidence plane and the wind direction relative to the scattering azimuth have negligible impact. By contrast, when the specular point lies in the vicinity of a localized maximum of brightness, scattering by the roughened ocean surface may reduce the glitter by more than 30%, as compared to a perfectly flat surface, and the glitter amplitude may vary by up to 0.7 K with variations in wind direction and by up to 0.5 K with variations in incidence plane orientation. It is shown that accounting for the roughness impact on celestial noise contamination is of particular concern for the remote sensing of SSS.
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Earth-Viewing L-Band Radiometer Sensing of Sea Surface Scattered Celestial Sky Radiation—Part II: Application to SMOS
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Nicolas Reul, Joseph Tenerelli, Nicolas Floury, Bertrand ChapronAbstract:We examine how the rough sea surface scattering of L-band celestial Sky Radiation might affect the measurements of the future European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. For this purpose, we combined data from several surveys to build a comprehensive all-Sky L-band celestial Sky brightness temperature map for the SMOS mission that includes the continuum Radiation and the hydrogen line emission rescaled for the SMOS bandwidth. We also constructed a separate map of strong and very localized sources that may exhibit L-band brightness temperatures exceeding 1000 K. Scattering by the roughened ocean surface of Radiation from even the strongest localized sources is found to reduce the contributions from these localized strong sources to negligible levels, and rough surface scattering solutions may be obtained with a map much coarser than the original continuum maps. In rough ocean surface conditions, the contribution of the scattered celestial noise to the reconstructed brightness temperatures is not significantly modified by the synthetic antenna weighting function, which makes integration over the synthetic beam unnecessary. The contamination of the reconstructed brightness temperatures by celestial noise exhibits a strong annual cycle with the largest contamination occurring in the descending swaths in September and October, when the specular projection of the field of view is aligned with the Galactic equator. Ocean surface roughness may alter the contamination by over 0.1 K in 30% of the SMOS measurements. Given this potentially large impact of surface roughness, an operational method is proposed to account for it in the SMOS level 2 sea surface salinity algorithm.
Chenxi Wang - One of the best experts on this subject based on the ideXlab platform.
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a fast all Sky Radiation model for solar applications with narrowband irradiances on tilted surfaces farms nit part ii the cloudy Sky model
Solar Energy, 2018Co-Authors: Yu Xie, Manajit Sengupta, Chenxi WangAbstract:Abstract The solar energy industry often uses individual steps to empirically compute plane-of-array (POA) irradiance from horizontal irradiance and decompose it to narrow-wavelength bands. Conventional radiative transfer models designed for meteorological applications requires significant computing efforts in practice; however, they provide a physics-based solution of radiance and therefore are capable of computing spectral POA irradiances in a single step. In this study, we integrate the advantages of the current models and develop an innovative radiative transfer model, the Fast All-Sky Radiation Model for Solar applications with Narrowband Irradiances on Tilted surfaces (FARMS-NIT), to efficiently compute irradiances on inclined photovoltaics (PV) panels for 2002 narrow-wavelength bands from 0.28 to 4.0 µm. This study is reported in two parts. Part I presents the methodology and performance evaluation of the new model under clear-Sky conditions. The Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS), which was designed to compute clear-Sky irradiances, is employed to rapidly provide the optical properties of a given clear-Sky atmosphere. The clear-Sky radiances in the narrow-wavelength bands are computed by considering three paths of photon transmission and solving the radiative transfer equation with the single-scattering approximation. The Bi-directional Transmittance Distribution Function (BTDF) of aerosols is given by their single-scattering phase function with a correction using a two-stream approximation. The validation analysis confirms that FARMS-NIT has improved accuracy compared to TMYSPEC as evaluated by both surface observations and a state-of-the-art radiative transfer model. This model substantially improves computational efficiency compared to other radiative transfer models though it uses slightly more computing time than TMYSPEC. Part II of this study addresses the model in cloud-Sky conditions and will be published as a companion paper.
Yu Xie - One of the best experts on this subject based on the ideXlab platform.
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a fast all Sky Radiation model for solar applications with narrowband irradiances on tilted surfaces farms nit part ii the cloudy Sky model
Solar Energy, 2018Co-Authors: Yu Xie, Manajit Sengupta, Chenxi WangAbstract:Abstract The solar energy industry often uses individual steps to empirically compute plane-of-array (POA) irradiance from horizontal irradiance and decompose it to narrow-wavelength bands. Conventional radiative transfer models designed for meteorological applications requires significant computing efforts in practice; however, they provide a physics-based solution of radiance and therefore are capable of computing spectral POA irradiances in a single step. In this study, we integrate the advantages of the current models and develop an innovative radiative transfer model, the Fast All-Sky Radiation Model for Solar applications with Narrowband Irradiances on Tilted surfaces (FARMS-NIT), to efficiently compute irradiances on inclined photovoltaics (PV) panels for 2002 narrow-wavelength bands from 0.28 to 4.0 µm. This study is reported in two parts. Part I presents the methodology and performance evaluation of the new model under clear-Sky conditions. The Simple Model of the Atmospheric Radiative Transfer of Sunshine (SMARTS), which was designed to compute clear-Sky irradiances, is employed to rapidly provide the optical properties of a given clear-Sky atmosphere. The clear-Sky radiances in the narrow-wavelength bands are computed by considering three paths of photon transmission and solving the radiative transfer equation with the single-scattering approximation. The Bi-directional Transmittance Distribution Function (BTDF) of aerosols is given by their single-scattering phase function with a correction using a two-stream approximation. The validation analysis confirms that FARMS-NIT has improved accuracy compared to TMYSPEC as evaluated by both surface observations and a state-of-the-art radiative transfer model. This model substantially improves computational efficiency compared to other radiative transfer models though it uses slightly more computing time than TMYSPEC. Part II of this study addresses the model in cloud-Sky conditions and will be published as a companion paper.
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Assessing the Performance of the Fast All-Sky Radiation Model for Solar Applications with Narrowband Irradiances on Tilted Surfaces (FARMS-NIT)
2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC 28th PVSEC & 34th EU PVSEC), 2018Co-Authors: Yu Xie, Manajit SenguptaAbstract:This study evaluates the performance of a new radiative transfer model, Fast All-Sky Radiation Model for Solar Applications with Narrowband Irradiances on Tilted surfaces (FARMS-NIT), that efficiently computes spectral irradiances on inclined photovoltaic (PV) panels. FARMS-NIT numerically solves the spatial distribution of solar Radiation in 2,002 wavelength bands, and thereby accurately provides plane-of-array (POA) irradiances by integrating radiances over inclined surfaces. The FARMS-NIT for clear-and cloudy-Sky conditions are used to compute POA irradiances for TMY3 sites and compared with the simulation by TMYSPEC. Our results indicate that FARMS-NIT leads to $\sim$ 5% greater spectral irradiances compared to TMYSPEC. The difference in POA irradiance with a latitude tilt angle is slightly larger than global horizonal irradiance (GHI).
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Fast All-Sky Radiation Model for Solar Applications (FARMS): A Brief Overview of Mechanisms, Performance, and Applications: Preprint
2016Co-Authors: Yu Xie, Manajit SenguptaAbstract:Solar Radiation can be computed using radiative transfer models, such as the Rapid Radiation Transfer Model (RRTM) and its general circulation model applications, and used for various energy applications. Due to the complexity of computing Radiation fields in aerosol and cloudy atmospheres, simulating solar Radiation can be extremely time-consuming, but many approximations--e.g., the two-stream approach and the delta-M truncation scheme--can be utilized. To provide a new fast option for computing solar Radiation, we developed the Fast All-Sky Radiation Model for Solar applications (FARMS) by parameterizing the simulated diffuse horizontal irradiance and direct normal irradiance for cloudy conditions from the RRTM runs using a 16-stream discrete ordinates radiative transfer method. The solar irradiance at the surface was simulated by combining the cloud irradiance parameterizations with a fast clear-Sky model, REST2. To understand the accuracy and efficiency of the newly developed fast model, we analyzed FARMS runs using cloud optical and microphysical properties retrieved using GOES data from 2009-2012. The global horizontal irradiance for cloudy conditions was simulated using FARMS and RRTM for global circulation modeling with a two-stream approximation and compared to measurements taken from the U.S. Department of Energy's Atmospheric Radiation Measurement Climate Research Facility Southern Great Plains site. Ourmore » results indicate that the accuracy of FARMS is comparable to or better than the two-stream approach; however, FARMS is approximately 400 times more efficient because it does not explicitly solve the radiative transfer equation for each individual cloud condition. Radiative transfer model runs are computationally expensive, but this model is promising for broad applications in solar resource assessment and forecasting. It is currently being used in the National Solar Radiation Database, which is publicly available from the National Renewable Energy Laboratory at http://nsrdb.nrel.gov.« less
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A Fast All-Sky Radiation Model for Solar applications (FARMS): Algorithm and performance evaluation
Solar Energy, 2016Co-Authors: Yu Xie, Manajit Sengupta, Jimy DudhiaAbstract:Abstract Radiative transfer (RT) models simulating broadband solar Radiation have been widely used by atmospheric scientists to model solar resources for various energy applications such as operational forecasting. Due to the complexity of solving the RT equation, the computation under cloudy conditions can be extremely time consuming though many approximations (e.g. two-stream approach and delta-M truncation scheme) have been utilized. Thus, a more efficient RT model is crucial for model developers as a new option for approximating solar Radiation at the land surface with minimal loss of accuracy. In this study, we developed a fast all-Sky Radiation model for solar applications (FARMS) using the simplified clear-Sky RT model, REST2, and simulated cloud transmittances and reflectances from Rapid Radiation Transfer Model (RRTM) with a sixteen-stream Discrete Ordinates Radiative Transfer (DISORT). Simulated lookup tables (LUTs) of cloud transmittances and reflectances are created by varying cloud optical thicknesses, cloud particle sizes, and solar zenith angles. Equations with optimized parameters are fitted to the cloud transmittances and reflectances to develop the model. The all-Sky solar irradiance at the land surface can then be computed rapidly by combining REST2 with the cloud transmittances and reflectances. This new RT model is more than 1000 times faster than those currently utilized in solar resource assessment and forecasting since it does not explicitly solve the RT equation for each individual cloud condition. Our results indicate the accuracy of the fast radiative transfer model is comparable to or better than two-stream approximation in term of computing cloud transmittance and solar Radiation.
Takeo S. Saitoh - One of the best experts on this subject based on the ideXlab platform.
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Advanced energy-efficient house (HARBEMAN house) with solar thermal, photovoltaic, and Sky Radiation energies (experimental results)
Solar Energy, 2001Co-Authors: Takeo S. Saitoh, Fujino TetsujiAbstract:Abstract An energy-independent residential house (‘HARBEMAN house’; Harmony BEtween Man And Nature), incorporating Sky Radiation cooling, solar thermal, and photovoltaic energies was built in Sendai, Japan during July, 1996. This paper reports monitored results of this house since September 1996 to date. The paper also presents simulation results for the HARBEMAN house and its results compared with the annual experimental data. The HARBEMAN house, which meets almost all the energy demands, including space heating and cooling, domestic hot water, electricity generated by photovoltaic cell and rainwater for standard Japanese homes. Sky Radiation cooling, solar thermal/photovoltaic (PV), and underground coolness as well as rainwater and waste heat are utilized in combination. Annual variations of water temperature in the underground main tank, heating/cooling/domestic hot water demands, collected and emitted heats by the solar collector and Sky radiator have been monitored.
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A highly-advanced solar house with solar thermal and Sky Radiation cooling
Applied Energy, 1999Co-Authors: Takeo S. SaitohAbstract:A unique energy-independent house ([`]HARBEMAN house'; HARmony BEtween Man And Nature) incorporating solar thermal, underground coolers, Sky Radiation cooling, photovoltaic electricity generation and rain-water collection was built in Sendai (latitude; 38° 17'00'' north and longitude; 140° 50'14'' east), Japan during July, 1996. The average solar energy received on a horizontal surface there in January is 7900 kJ/m2/day. This paper reports the experimental results since September 1996 to date. The annual variations of water temperature in the underground main tank, heating /cooling/domestic hot water demands, collected and emitted heats by solar collector and Sky radiator, were measured. The paper also clarifies the method of computer simulation results for the HARBEMAN house and its results compared with the annual experimental data. The proposed HARBEMAN house, which meets almost all its energy demands, including space heating and cooling, domestic hot water, electricity generated by photovoltaic cell and rainwater for standard Japanese homes. The proposed system has two operational modes: (i) a long-term thermal energy storage mode extending from September to March and (ii) a long-term cool storage mode extending from April to August. The system is intended to utilize as little energy as possible to collect and emit the heat. This paper also clarifies the primary energy consumption, the external costs (externalities) and the means for the reduction of carbon-dioxide (CO2) emissions. The primary-energy consumption and carbon-dioxide emissions of the proposed house are only one-tenth of those of the conventional standard house. Moreover, the thermal performance of this house will be compared with the results of the IEA solar low-energy house TASK 13. Finally, this paper validates the external costs of this house, which have been intensively discussed in recent years in European countries. The present energy-sufficient house will be attempting in 21st century to reduce carbon dioxide emissions, which will be one of the key factors for mitigating global warming.
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An advanced low-energy and CO{sub 2} emission-free house (HARBEMAN house) with Sky Radiation cooling
1999Co-Authors: Takeo S. Saitoh, T. FujinoAbstract:A unique energy-independent house (HARBEMAN house--Harmony Between Man and Nature) incorporating Sky Radiation cooling and solar thermal, underground coolness and so on was built as a residential house in Sendai, Japan (latitude; 38 deg. 17{prime}00{double_prime} north and longitude; 140 deg. 50{prime}14{double_prime} east) in 1996. The average solar energy received on a horizontal surface in January in Sendai is 7,200 kJ/m{sup 2}/day. This paper describes the experimental results of this sophisticated house since September 1996 to date. The paper also reports the method of computer simulation for the HARBEMAN house and the results compared with the annual experimental data for 1997 and 1998. The proposed HARBEMAN house meets almost all its energy demands, including space heating and cooling, domestic hot water, electricity generated by photovoltaic cell and rainwater for the Japanese standard homes. Sky Radiation cooling, solar thermal/PV and natural underground coolness cooling as well as rainwater and waste heat are combinedly utilized.
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A high-tech low-energy house with solar thermal and Sky Radiation cooling
1998Co-Authors: Takeo S. Saitoh, Fujino Tetsuji, Masanori SuzukiAbstract:A unique energy-independent house (HARBEMAN HOUSE; HARmony BEtween Man And Nature) incorporating solar thermal, underground coolness, Sky Radiation cooling, photovoltaic electricity generation and rain water was built in Sendai, Japan on July, 1996. The average solar energy received on a horizontal surface in January is 7900 kJ/m{sup 2}/day. This paper reports the experimental results since September 1996 to date. The annual variations of water temperature in the underground main tank, heating/cooling/domestic hot water demands, collected and emitted heats by solar collector and Sky radiator, were obtained by the measured data. The paper also clarifies the method of computer simulation results for the HARBEMAN HOUSE and its results compared with the annual experimental data. The proposed HARBEMAN house, which meets almost all its energy demands, including space heating and cooling, domestic hot water, electricity generated by photovoltaic cell and rainwater for standard Japanese homes. The proposed system has two operational modes: (i) a long-term thermal energy storage mode extending from September to next March and (ii) a long-term cool storage mode extending from April to August. The system is intended to utilize as little energy as possible to collect and emit the heat. This paper also clarifies the primary energy consumption,more » the external costs (externalities) and the effect for reduction of carbon dioxide (CO2) emissions. The primary energy consumption and carbon dioxide emissions of the proposed house are only one-tenth of these of the conventional standard house. Finally, this paper validates the external costs of this house, which have been intensively discussed in recent years in European countries. The present energy-sufficient house will be promising in the 21st century to reduce carbon dioxide emissions, which will be one of the key factors for mitigating global warming.« less
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A theoretical model for an open system with Sky Radiation cooling and solar Radiation
1995Co-Authors: Takeo S. Saitoh, Yotaro Yanamoto, Junzo ShinomiyaAbstract:Since the atmosphere of the earth is relatively transparent in the infrared (i.r.) wave length region between 8 and 13 {mu}m, what the authors call the atmospheric window, a part of the thermal Radiation at the surface of the earth is lost into space and cooling takes place. This phenomenon is referred to as Sky Radiation cooling. In this paper, the combined heat transfer simulation was performed for a water reservoir undergoing Sky Radiation cooling as well as solar Radiation, evaporation, convective heat transfer and heat conduction to the soil. Examples of applications considered here are warming of rice field water, swimming pools, breeding reservoirs, and solar ponds. The present study will provide good information to cope with the unusual cold weather experienced during the summer of 1993 in Japan. According to the present analysis, the water temperature of a rice field can be considerably raised and, as a result, a bad harvest avoided.
Nicolas Reul - One of the best experts on this subject based on the ideXlab platform.
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earth viewing l band radiometer sensing of sea surface scattered celestial Sky Radiation part i general characteristics
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Joseph Tenerelli, Nicolas Reul, Alexis Mouche, Bertrand ChapronAbstract:The ldquogalactic glitterrdquo phenomenon at L-band, i.e., the scattering of celestial Sky Radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident celestial brightness is uniform, sea surface roughness has a negligible impact on the glitter. At such a point, variations in both the orientation of the incidence plane and the wind direction relative to the scattering azimuth have negligible impact. By contrast, when the specular point lies in the vicinity of a localized maximum of brightness, scattering by the roughened ocean surface may reduce the glitter by more than 30%, as compared to a perfectly flat surface, and the glitter amplitude may vary by up to 0.7 K with variations in wind direction and by up to 0.5 K with variations in incidence plane orientation. It is shown that accounting for the roughness impact on celestial noise contamination is of particular concern for the remote sensing of SSS.
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earth viewing l band radiometer sensing of sea surface scattered celestial Sky Radiation part ii application to smos
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Nicolas Reul, Joseph Tenerelli, Nicolas Floury, Bertrand ChapronAbstract:We examine how the rough sea surface scattering of L-band celestial Sky Radiation might affect the measurements of the future European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. For this purpose, we combined data from several surveys to build a comprehensive all-Sky L-band celestial Sky brightness temperature map for the SMOS mission that includes the continuum Radiation and the hydrogen line emission rescaled for the SMOS bandwidth. We also constructed a separate map of strong and very localized sources that may exhibit L-band brightness temperatures exceeding 1000 K. Scattering by the roughened ocean surface of Radiation from even the strongest localized sources is found to reduce the contributions from these localized strong sources to negligible levels, and rough surface scattering solutions may be obtained with a map much coarser than the original continuum maps. In rough ocean surface conditions, the contribution of the scattered celestial noise to the reconstructed brightness temperatures is not significantly modified by the synthetic antenna weighting function, which makes integration over the synthetic beam unnecessary. The contamination of the reconstructed brightness temperatures by celestial noise exhibits a strong annual cycle with the largest contamination occurring in the descending swaths in September and October, when the specular projection of the field of view is aligned with the Galactic equator. Ocean surface roughness may alter the contamination by over 0.1 K in 30% of the SMOS measurements. Given this potentially large impact of surface roughness, an operational method is proposed to account for it in the SMOS level 2 sea surface salinity algorithm.
-
Earth-Viewing L-Band Radiometer Sensing of Sea Surface Scattered Celestial Sky Radiation—Part I: General Characteristics
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Joseph Tenerelli, Nicolas Reul, Alexis Mouche, Bertrand ChapronAbstract:The ldquogalactic glitterrdquo phenomenon at L-band, i.e., the scattering of celestial Sky Radiation by the rough ocean surface, is examined here as a potential source of error for sea surface salinity (SSS) remote sensing. We begin by considering the transformations that must be applied to downwelling celestial noise in order to compute the eventual impact on the antenna temperature. Then, outside the context of any particular measurement system, we use approximate scattering models along with a model for the equilibrium wind wave spectrum to examine how the scattered signal at the surface might depend on the geophysical conditions and scattering geometry. It is found that, when the specular point lies far away from the galactic plane, where the incident celestial brightness is uniform, sea surface roughness has a negligible impact on the glitter. At such a point, variations in both the orientation of the incidence plane and the wind direction relative to the scattering azimuth have negligible impact. By contrast, when the specular point lies in the vicinity of a localized maximum of brightness, scattering by the roughened ocean surface may reduce the glitter by more than 30%, as compared to a perfectly flat surface, and the glitter amplitude may vary by up to 0.7 K with variations in wind direction and by up to 0.5 K with variations in incidence plane orientation. It is shown that accounting for the roughness impact on celestial noise contamination is of particular concern for the remote sensing of SSS.
-
Earth-Viewing L-Band Radiometer Sensing of Sea Surface Scattered Celestial Sky Radiation—Part II: Application to SMOS
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Nicolas Reul, Joseph Tenerelli, Nicolas Floury, Bertrand ChapronAbstract:We examine how the rough sea surface scattering of L-band celestial Sky Radiation might affect the measurements of the future European Space Agency Soil Moisture and Ocean Salinity (SMOS) mission. For this purpose, we combined data from several surveys to build a comprehensive all-Sky L-band celestial Sky brightness temperature map for the SMOS mission that includes the continuum Radiation and the hydrogen line emission rescaled for the SMOS bandwidth. We also constructed a separate map of strong and very localized sources that may exhibit L-band brightness temperatures exceeding 1000 K. Scattering by the roughened ocean surface of Radiation from even the strongest localized sources is found to reduce the contributions from these localized strong sources to negligible levels, and rough surface scattering solutions may be obtained with a map much coarser than the original continuum maps. In rough ocean surface conditions, the contribution of the scattered celestial noise to the reconstructed brightness temperatures is not significantly modified by the synthetic antenna weighting function, which makes integration over the synthetic beam unnecessary. The contamination of the reconstructed brightness temperatures by celestial noise exhibits a strong annual cycle with the largest contamination occurring in the descending swaths in September and October, when the specular projection of the field of view is aligned with the Galactic equator. Ocean surface roughness may alter the contamination by over 0.1 K in 30% of the SMOS measurements. Given this potentially large impact of surface roughness, an operational method is proposed to account for it in the SMOS level 2 sea surface salinity algorithm.