Comparing a hyperspectral Monte-Carlo approach for simulating water surface reflectance signatures based upon radiative transfer theory: simulating clear water Caribbean Sea bottom types

摘要

A homogeneous water column hyperspectral Monte Carlo modeling approach is compared to an analytical solution to a radiative transfer model system for irradiance. Both mathematical models and the solution approaches describe the transfer of irradiant light in a homogeneous medium. The analytical model has been previously used to describe the transfer of irradiant energy in a homogenous water column, with and without fluorescence source terms as well as a direct specular or a collimated irradiance source term. The response of the water surface reflectance under solar irradiance or an artificial collimated light source is thus modeled. Synthetic reflectance signatures generated from the 2 mathematical models describe the interaction of irradiant photon flux in terms of the 2 flow irradiance equations. The Monte Carlo model is used for creating synthetic coastal water color or reflectance signatures for clear waters with different bottom reflectance signatures using data collected in the Caribbean Sea region. The analytical model has suggested proportionality between the absorption and backscatter coefficients around 0.29. In this paper the proportionality factor'for clear water using the Monte Carlo model of irradiance was found to vary, but averaged around 0.26. This compares to 0.33 from other published values used in simple remote sensing algorithms. Results suggest that the optical pathlength (the maximum distance a photon travels before interaction (scattering or absorption) within the medium) will be a dominant factor influencing the ability of the Monte Carlo model to accurately represent measured or known reflectance signatures. The hyperspectral Monte Carlo mathematical modeling results also suggest the value of the technique for calculating the backscattering coefficient in waters with varying suspended matter, dissolved organic matter (DOM) and phytoplankton pigments.