The reflection of ocean surface is often assumed azimuthally symmetric in the previous vector discrete ordinate radiative transfer(VDISORT)and many other radiative transfer solvers.This assumption can lead to obvious ...The reflection of ocean surface is often assumed azimuthally symmetric in the previous vector discrete ordinate radiative transfer(VDISORT)and many other radiative transfer solvers.This assumption can lead to obvious errors in the simulated radiances.In this study,the vector radiative transfer equation is solved with a polarized bidirectional reflection distribution function(pBRDF)for computing the surface-leaving radiation from the lower boundary.An azimuthally asymmetric pBRDF model at visible and infrared bands over oceans is fully coupled with the updated VDISORT model.The radiance at the ocean surface is combined with the contributions of atmospheric scattering and surface properties.It is shown that the radiance at the ocean surface also exhibits a strong angular dependence in the Stokes vector and the magnitudes of I.Q.and V increase for a larger azimuthal dependence of pBRDF.In addition,the solar position affects the peaks of sun glitter pattern,thus modulating the signal magnitudes and the angular distributions.As ocean wind increases,the reflection weakens with reduced magnitudes of Stokes parameters and lessvarying angular distributions.展开更多
An expression of degree of polarization（DOP） for metallic material is presented based on the three-component polarized bidirectional reflectance distribution function（p BRDF） model with considering specular reflec...An expression of degree of polarization（DOP） for metallic material is presented based on the three-component polarized bidirectional reflectance distribution function（p BRDF） model with considering specular reflection, directional diffuse reflection and ideal diffuse reflection. The three-component p BRDF model with a detailed reflection assumption is validated by comparing simulations with measurements. The DOP expression presented in this paper is related to surface roughness, which makes it more reasonable in physics. Test results for two metallic samples show that the DOP based on the three-component p BRDF model accords well with the measurement and the error of existing DOP expression is significantly reduced by introducing the diffuse reflection. It indicates that our DOP expression describes the polarized reflection properties of metallic surfaces more accurately.展开更多
The ocean surface emissivity model plays a pivotal role in satellite data assimilation and the retrieval of ocean physical parameters.In our previous research,we developed a physical emissivity model featuring a polar...The ocean surface emissivity model plays a pivotal role in satellite data assimilation and the retrieval of ocean physical parameters.In our previous research,we developed a physical emissivity model featuring a polarized Bidirectional Reflectance Distribution Function(pBRDF-E).This model effectively ensures the consistency between surface emission and reflection parameters.However,it suffers from low computational efficiency.In this study,we introduce a fast ocean emissivity model,OceanEM.Leveraging the emissivity data output from the pBRDF-E model,OceanEM is developed by using a multilayer perceptron neural network.It can compute the polarization emissivity vector across a wide range of conditions:incidence angles from 0°to 80°,wind speeds from 2 to 50 m s^(-1),sea surface temperatures from-2°to 30℃,sea surface salinities from 0 to 40 psu,and frequencies from 1.4 to 410 GHz.Alongside the FAST Microwave Emissivity Model(FASTEM6)and SURface Fast Emissivity Model for Ocean(SURFEM-ocean),OceanEM is integrated into the Advanced Radiative Transfer Modeling System(ARMS)as a user-selectable option.To validate the accuracy of OceanEM,we compare it with FASTEM6 and SURFEM-ocean using data from WindSAT,a polarimetric radiometer onboard the Coriolis satellite.The results show that the three models generally yield consistent simulations of WindSAT brightness temperatures.Specifically,for channels at 6.8GHz,10.7 GHz(both horizontal and vertical polarization),and 18.7 GHz(vertical polarization),OceanEM demonstrates higher accuracy than FASTEM6 but lower than SURFEM-ocean.Conversely,for channels of 18.7 GHz(horizontal polarization),23.8 GHz,and 37.0 GHz(both horizontal and vertical polarization),OceanEM outperforms both FASTEM6 and SURFEM-ocean.展开更多
基金Supported by the National Natural Science Foundation of China(U2142212 and U2242211),Hunan Provincial Natural Science Foundation of China(2021JC0009)National Key Research and Development Program of China[2019QZKK(Qinghai Tibet KeKao)].
文摘The reflection of ocean surface is often assumed azimuthally symmetric in the previous vector discrete ordinate radiative transfer(VDISORT)and many other radiative transfer solvers.This assumption can lead to obvious errors in the simulated radiances.In this study,the vector radiative transfer equation is solved with a polarized bidirectional reflection distribution function(pBRDF)for computing the surface-leaving radiation from the lower boundary.An azimuthally asymmetric pBRDF model at visible and infrared bands over oceans is fully coupled with the updated VDISORT model.The radiance at the ocean surface is combined with the contributions of atmospheric scattering and surface properties.It is shown that the radiance at the ocean surface also exhibits a strong angular dependence in the Stokes vector and the magnitudes of I.Q.and V increase for a larger azimuthal dependence of pBRDF.In addition,the solar position affects the peaks of sun glitter pattern,thus modulating the signal magnitudes and the angular distributions.As ocean wind increases,the reflection weakens with reduced magnitudes of Stokes parameters and lessvarying angular distributions.
文摘An expression of degree of polarization（DOP） for metallic material is presented based on the three-component polarized bidirectional reflectance distribution function（p BRDF） model with considering specular reflection, directional diffuse reflection and ideal diffuse reflection. The three-component p BRDF model with a detailed reflection assumption is validated by comparing simulations with measurements. The DOP expression presented in this paper is related to surface roughness, which makes it more reasonable in physics. Test results for two metallic samples show that the DOP based on the three-component p BRDF model accords well with the measurement and the error of existing DOP expression is significantly reduced by introducing the diffuse reflection. It indicates that our DOP expression describes the polarized reflection properties of metallic surfaces more accurately.
基金Supported by the National Key Research and Development Program of China(2021YFB3900400)National Natural Science Foundation of China(U2142212)。
文摘The ocean surface emissivity model plays a pivotal role in satellite data assimilation and the retrieval of ocean physical parameters.In our previous research,we developed a physical emissivity model featuring a polarized Bidirectional Reflectance Distribution Function(pBRDF-E).This model effectively ensures the consistency between surface emission and reflection parameters.However,it suffers from low computational efficiency.In this study,we introduce a fast ocean emissivity model,OceanEM.Leveraging the emissivity data output from the pBRDF-E model,OceanEM is developed by using a multilayer perceptron neural network.It can compute the polarization emissivity vector across a wide range of conditions:incidence angles from 0°to 80°,wind speeds from 2 to 50 m s^(-1),sea surface temperatures from-2°to 30℃,sea surface salinities from 0 to 40 psu,and frequencies from 1.4 to 410 GHz.Alongside the FAST Microwave Emissivity Model(FASTEM6)and SURface Fast Emissivity Model for Ocean(SURFEM-ocean),OceanEM is integrated into the Advanced Radiative Transfer Modeling System(ARMS)as a user-selectable option.To validate the accuracy of OceanEM,we compare it with FASTEM6 and SURFEM-ocean using data from WindSAT,a polarimetric radiometer onboard the Coriolis satellite.The results show that the three models generally yield consistent simulations of WindSAT brightness temperatures.Specifically,for channels at 6.8GHz,10.7 GHz(both horizontal and vertical polarization),and 18.7 GHz(vertical polarization),OceanEM demonstrates higher accuracy than FASTEM6 but lower than SURFEM-ocean.Conversely,for channels of 18.7 GHz(horizontal polarization),23.8 GHz,and 37.0 GHz(both horizontal and vertical polarization),OceanEM outperforms both FASTEM6 and SURFEM-ocean.
