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Publicly available 3D radiative transfer codes

• comparison of stochastic methods for generating heterogeneous cloud structures
• matlab programs for stochastic cloud generation using IAAFT (Iterative Amplitude Adapted Fourier Transform) algorithm
• The IAAFT model is described in Venema, V., S. Meyer, S. Gimeno García, A. Kniffka, C. Simmer, S. Crewell, U. Löhnert, T. Trautmann, and A. Macke, 2006: Surrogate cloud fields generated with the Iterative Amplitude Adapted Fourier Transform algorithm. Tellus, 58A, 104-120. [Abstract] [Full paper (PDF 1.2 MB)]

• Generates 3D cloud (specifically Cirrus) structures
• Program is in C and requires publicly available FFTW and NetCDF libraries installed (links provided at CLOUDGEN web site)
• Site includes illustrations, publications, and presentations on 3D Cirrus cloud structures
• Model is described in Hogan, R. J., and S. F. Kew, 2005: A 3D stochastic cloud model for investigating the radiative properties of inhomogeneous cirrus clouds. Q. J. R. Meteorol. Soc., 131, 2585-2608. [Full paper (PDF 2.3 MB)]

• Simulated cloud structure is determined by a small number of parameters including power-law scaling and variance of cloud water path.
• Horizontal 2D variability is generated by a stochastic model.
• Vertical variability follows idealized profiles based on the total water path and temperature appropriate for the modeled regime (e.g. stratocumulus).
• Model is described in Di Giuseppe, F., and A. M. Tompkins, 2003: Effect of spatial organisation on solar radiative transfer in three dimensional idealised stratocumulus cloud fields. J. Atmos. Sci., 60, 1774-1794. [Full paper (PDF 1.8 MB)]

• This fast model generates 2D fields of two correlated variables (e.g., geometrical and optical thicknesses, or optical thickness and droplet effective radius) that have the same PDF and spatial correlation statistics as an observed cloud field provided to the model as input. For details, see this manuscript (PDF 2.2 MB).
• An earlier version of the code (generating 2D fields of only one variable) is described in Prigarin, S. M., and A. Marshak, 2005: Numerical model of broken clouds adapted to observations. Atmospheric and Oceanic Optics, 18, 236-242. [Abstract] [Full paper (PDF 300 KB)]
• At present, the model runs only on Windows PCs. For more information, please contact the authors.

• Generates 3-D clouds based on aircraft observations along multiple flight paths.
• Horizontal structure is reconstructed assuming similar autocorrelation functions along and across flight directions.
• Publicly available code is written in Fortran 90.
• Model is described in Schmidt, K. S., V. Venema, F. Di Giuseppe, R. Scheirer, M. Wendisch, P. Pilewskie, 2007: Reproducing cloud microphysical and irradiance measurements using three 3D cloud generators. Quart. J. Royal Meteor. Soc., 133, Part A, 765-780. [Abstract]

• Generates ensemble of 1D cloud masks according to a (continuous) statistical cell model (Alexandrov, 2010) with given cell occupation probability and sample length (specified as the number of cells in the sample). Then, analyzes this ensemble deriving statistical distributions of cloud/gap lengths and cloud fraction, which are compared with theoretical results.
• Program is in IDL. Program type is "main" (edit the parameters in the program's header, then compile/run using ".r" command). Creates plots (in EPS format) similar to Figs. 2-7 in Alexandrov (2010)
• The model is described in Alexandrov, M. D., A. Marshak, and A. S. Ackerman, 2010: Cellular statistical models of broken cloud fields. Part I: Theory. J. Atmos. Sci., 67, 2125-2151, doi:10.1175/2010JAS3364.1. [Abstract] [Full paper (PDF 156 KB)] and compared with LES output in Alexandrov, M. D., A. Marshak, and A. S. Ackerman, 2010: Cellular statistical models of broken cloud fields. Part II: Comparison with dynamical model, statistics of diverse ensembles. J. Atmos. Sci., 67, 2152-2170, doi:10.1175/2010JAS3365.1. [Abstract] [Full paper (PDF 156 KB)]

• Includes theory and illustrations of bounded cascades, a widely used method for generating heterogeneous cloud structures (including in GCMs)
• Bounded cascades also described in Cahalan, R. F., 1994: Bounded cascade clouds albedo and effective thickness. Nonlinear Proc. Geophys., 1, 156-167. [Abstract] [Full paper (PDF 1.1 MB)]
• No public code is available at this time.

• Includes theory and illustrated examples of fractal cloud generation
• No public code is available at this time.