Formulas that express the optical thickness and the single scattering albedo (or volume scattering and absorption coefficients) through hemispherical irradiance inside optically thick and horizontally homogeneous extended cloud are derived for short-wave spectral ranges. A cloud with vertical heterogeneity and a multilayer cloud system are considered. The evaluation of uncertainties and applicability limits for these formulas is carried out. The formulas are applied to the interpretation of spectral radiation measurements taken during two aircraft field experiments. The spectral dependence of these optical parameters for different cloud sublayers is found and presented. ¿ 2001 American Geophysical Union