Reflection and transmission of solar light by clouds: asymptotic theory

A. A. Kokhanovsky (1) , T. Nauss (2)

1 Institute of Remote Sensing
2 LCRS - Laboratory for Climatology and Remote Sensing [Marburg]

The authors introduce the radiative transfer model CLOUD for reflection, transmission, and absorption characteristics of terrestrial clouds and discuss the accuracy of the approximations used within the model. A Fortran implementation of CLOUD is available for download. This model is fast, accurate, and capable of calculating multiple raditiative transfer characteristics of cloudy media including the spherical and plane albedo, reflection and transmission functions, absorptance as well as global and diffuse transmittance. The approximations are based on the asymptotic solutions of the radiative transfer equations.

While the analytic part of the solutions is treated in the code in an approximate way, the correspondent reflection function (RF) of a semi-infinite water cloud R_? is calculated using numerical solutions of the radiative transfer equations in the assumption of Deirmendjian's cloud C1 model. In the case of ice clouds, the fractal ice crystal model is used. The resulting values of R_? with respect to the viewing geometry are stored in a look-up table (LUT).

Domaines: Océan, Atmosphère

A. A. Kokhanovsky, T. Nauss. Reflection and transmission of solar light by clouds: asymptotic theory. Atmospheric Chemistry and Physics Discussions, 2006, 6 (4), pp.8301-8334. ⟨hal-00302091⟩