Define how liquid water content and effective droplet radius are translated to optical properties.
wc_properties type
Possible choices for type are
hu

Parameterization by Hu and Stamnes (1993); this is the default setting. Note that the parameterization is somewhat different for correlated_k FU than for all other cases because in the latter case the parameterization from the newer (March 2000) Fu and Liou code is used while otherwise the data are taken from the original paper by Hu and Stamnes (1993). Note that this parameterization has been developed to calculate irradiances, hence it is less suitable for radiances. This is due to the use of the Henyey-Greenstein phase function as an approximation of the real Mie phase function.
echam4

Use the very simple two-band parameterization of the ECHAM4 climate model, described in Roeckner et al. (1996); this is probably only meaningful if you want to compare your results with ECHAM4, the two bands are 0.2 - 0.68 micrometer and 0.68 - 4.0 micrometer; within these bands, the optical properties are assumed constant.
mie

Use pre-calculated Mie tables; useful for correlated_k; the tables are expected in data_files_path/correlated_k/../.For spectral or pseudo-spectral (correlated_k sbdart) calculations, a set of pre-calculated tables is also available; the wavelength grid points of these data has been carefully selected such that the extinction cross section, single scattering albedo, and the asymmetry parameter are accurate to 1% (compared to the fully-resolved Mie calculation) for all wavelengths between 250nm and 100 micrometer. For spectral or pseudo-spectral calculations wc_properties_interpolate has to be defined explicitely to initiate the interpolation of the optical properties to the internal wavelength grid. Please note that this option may be extremely memory-consuming because for each internal wavelength a full set of Legendre moments of the phase function is stored (up to several thousands). The Mie tables are not part of the standard distribution (because of their large size) but they are freely available from http://www.libradtran.org. This is the correct option to calculate radiances, to be preferred over the Henyey-Greenstein approach of Hu and Stamnes (1993).
filename

Read optical properties from specified filename; file format is as produced by the mie-tool of the libRadtran package(see output_user cloudprp) or by Frank Evans' cloudprp; for each of the internal (computational) wavelengths, a separate file is expected. Use only if you really know what you are doing (this option is subject to change).





Arve Kylling 2010-03-10