Single-scattering albedo A_S(λ) (left column) and extinction cross section C_ext [cm²] (right column) as a function of wavelength at selected pressure levels. Calculated with (solid) and without (dashed) a distribution of hollow spheres for the T_eff = 1800 K, log(g) = 3.0 profile. Shown are the pressure levels nearest to 10⁻¹⁰, 10⁻⁵, and 10⁻³ bar (top, middle, and bottom panels). These levels are representative of the upper atmosphere, the typical lowest pressure of general circulation models, and the regime where transmission observations are sensitive, respectively. Four cloud particle cases are shown: monodisperse distribution of compact particles (black), Gaussian distribution of compact particles (red), monodisperse distribution of highly micro-porous particles f_por = 0.9 (blue), and Gaussian distribution of highly micro-porous particles (green).