|
Applications involving surveillance, tracking, identification, and modeling of objects on the ocean surface require a knowledge of the visible and infrared radiation incident on that surface. This model allows the user to compute the spectral and band-averaged radiance from the sky for any view angle. The model formulations are based upon an analytic solution of the radiative-transfer equation using an advanced two-stream approximation for the up-welling and downwelling radiation fields. The boundary condition at the lower surface is fulfilled by the use of a diffuse spectral reflectance and a diffuse spectral emissivity. Single and multiple scattering and emission by the maritime aerosols are included by the use of a three-component Navy aerosol model for the boundary layer. The vertical aerosol density profiles are characterized by Fermi-Dirac and exponential distributions with scale heights that are different for each of the three aerosol components. The indices of refraction as well as the sizes of the particulates are functions of the wavelength and the relative humidity. A subroutine in the computerized version of the model explicitly computes the volume attenuation coefficients, the single-scattering albedo, and the single-scattering phase function for use in the sky radiance formulas. The user has the option of implementing any of six standard vertical temperature profiles or he can use his own temperature data. The multiple scattering of the atmospheric and sea-surface thermally emitted radiation is treated in a mathematically exact way by fitting the Planck radiance to a series of exponential functions in optical depth. The model input parameters consist of: current wind speed, 24-hour average wind speed, relative humidity, air mass, ocean temperature, air temperature profile, wavelength, the day of the year, Sun angles, and view angle. Output quantities are: sky radiance and solar irradiance for any wavelength from the visible to 40 micrometers.
|
