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The presented adjacency correction algorithm is based on the use of the point spread function (PSF) which allows calculating the contribution of reflections from the nearby pixels to the apparent radiance of the target. The analytical expression of the PSF for an arbitrary stratified atmosphere is obtained in the approximation of primary scattering, whereas the full equation of radiative transfer is used for the estimation of the radiance reflected from the surface. The algorithm is sensor independent and can be applied for processing images of water basins with arbitrary shape of the shore line and under different geometries of observation. The program using this algorithm is included in Modular Inversion Program — MIP (Heege et al., 2014) for processing of satellite images on a routine basis. Examples of processing results are presented in the paper.

An extensive comparison between radiative transfer codes in the atmosphere–ocean system is proposed and performed. The full angular radiance distribution at several optical depths in atmosphere and water is intercompared on a set of idealized problems designed to study codes’ accuracy in modeling separate, specific system features. In-water profiles of upwelling nadir radiance, upwelling and downwelling irradiance are intercompared for a realistic case extracted from an experimental data set. Two models are involved: the FEM numerical algorithm, based on the finite element method, and the P HO-TRAN 3D backward Monte Carlo code. The results show an optimal agreement between the codes under any condition. Codes’ relative differences are always lower than the estimated statistical error on the P HO-TRAN results.

A methodology has been developed and applied to accurately quantify and analyze adjacency effects in satellite ocean color data for a set of realistic and representative observation conditions in the northern Adriatic Sea. The study, properly accounting for sea surface reflectance anisotropy, off-nadir views, coastal morphology and atmospheric multiple scattering, include a sensitivity analysis on commonly applied approximations. Results indicate that, within the accuracy limits defined by the radiometric resolution of the ocean color sensors, adjacency effects in coastal waters might be significant at both visible and NIR wavelengths up to several km off the coast. These results additionally highlight a significant dependence on the angle of observation, on the directional reflectance properties of the sea surface, and on the atmospheric multiple scattering., JRC.H.1-Water Resources

Accurate radiative transfer modeling in the coupled atmosphere-sea system is increasing in importance for the development of advanced remote-sensing applications. Aiming to quantify the uncertainties in the modeling of coastal water radiometric quantities, we performed a closure experiment to intercompare theoretical and experimental data as a function of wavelength lambda and water depth z. Specifically, the study focused on above-water downward irradiance E(d)(lambda, 0+) and in-water spectral profiles of upward nadir radiance L(u)(lambda, z), upward irradiance E(u)(lambda, z), downward irradiance E(d)(lambda, z), the E(u)(lambda, z)/L(u)(lambda, z) ratio (the nadir Q factor), and the E(u)(lambda, z)/E(d)(lambda, z) ratio (the irradiance reflectance). The theoretical data were produced with the finite-element method radiative transfer code ingesting in situ atmospheric and marine inherent optical properties. The experimental data were taken from a comprehensive coastal shallow-water data set collected in the northern Adriatic Sea. Under various measurement conditions, differences between theoretical and experimental data for the above-water E(d)(lambda, 0+) and subsurface E(d)(lambda, 0-) as well as for the in-water profiles of the nadir Q factor were generally less than 15%. In contrast, the in-water profiles of L(u)(lambda, z), E(d)(lambda, z), E(u)(lambda, z) and of the irradiance reflectance exhibited larger differences [to approximately 60% for L(u)(lambda, z) and E(u)(lambda, z), 30% for E(d)(lambda, z), and 50% for the irradiance reflectance]. These differences showed a high sensitivity to experimental uncertainties in a few input quantities used for the simulations: the seawater absorption coefficient; the hydrosol phase function backscattering probability; and, mainly for clear water, the bottom reflectance.

The finite element method (FEM) is applied to solve the problem of transfer of unpolarised monochromatic radiation in a multi-layered nonuniformly refractive medium, i.e. the coupled atmosphere-ocean system. The resulting model ensures energy conservation independently of the adopted phase function, the number of grid points and the relative refractive index. The theoretical basis is here presented together with a number of applications on realistic atmosphere-ocean systems.

The presence of an aerosol layer over a nonuniform surface causes the blurring effect in remotely sensed images. In principle from the study of this effect it seems to be possible to evaluate aerosol properties. In this paper an aerosol layer superimposed on a surface with 1-D periodical variation in reflectivity and with half plane reflectivity variation is considered, in the single scattering approximation.

Scattering from atmospheric aerosols causes blurring of satellite images. A study of this effect suggests that it might be possible to evaluate aerosol properties from these images. We consider an aerosol layer superimposed on a surface with a one-dimensional sinusoidal variation in reflectivity and with a half-plane reflectivity variation. A single scattering approximation is used to show that information about the aerosol layer height and optical depth can be extracted provided the variation in ground reflectivity is known.