Plane-parallel SHDOM for Data Assimilation (SHDOMPPDA)


This web page is the distribution point for two closely related radiative transfer models. SHDOMPP is the plane-parallel version of SHDOM. SHDOMPPDA is a version of SHDOMPP for data assimilation. SHDOMPPDA includes forward, tangent linear, and adjoint models of SHDOMPP packaged in a Fortran 90 module with a easy to use interface.

SHDOMPP computes unpolarized radiative transfer in a plane-parallel medium for either collimated solar and/or thermal emission sources of radiation. Currently Lambertian and RPV land surface BRDF surface reflection are supported. The atmosphere optical properties are specified with an input file listing the layer interface heights and temperatures, and layer optical depth, single scattering albedo, and Legendre series coefficients of the phase function. Two output files are generated: one with the upwelling and downwelling hemispheric fluxes and actinic fluxes at the layer boundaries and another with radiances at specified heights and directions. The SHDOMPP calculation may be either monochromatic or spectrally integrated with a k-distribution.

SHDOMPPDA inputs pressure, temperature, water vapor, and ozone profiles, and mixing ratio and number concentration profiles for any number of hydrometeor species. The pressure, temperature, water vapor and ozone profiles are passed to user provided molecular absorption routines (i.e. an interface for molecular absorption routines is provided, but actual algorithms are not). SHDOMPPDA includes optical property calculations using scattering tables as a function of mass mean radius. Mass mean radius is chosen instead of effective radius because it can be directly calculated from the input hydrometeor mass mixing ratio and number concentration without further assumptions about the particle size distribution and shape. Molecular Rayleigh scattering is calculated for wavelengths shorter than 1 micron. The SHDOMPPDA forward radiative transfer routine calculates the top of atmosphere monochromatic radiances (in reflectance units or brightness temperature) for a number of specified directions for a single input column of properties.


A journal article on the SHDOMPP and SHDOMPPDA algorithms has been published and is available as a PDF file (870 kB). (Evans, K. F., 2007: SHDOMPPDA: A radiative transfer model for cloudy sky data assimilation. J. Atmos. Sci., 64, 3858-3868.) The SHDOMPP documentation file has the input file format, list of input parameters, information about running SHDOMPP and other programs in the distribution, and a list of files in the distribution.

The SHDOMPPDA documentation file has an overview of the SHDOMPPDA_FWD_TL_ADJ module, description of arguments for key routines, information about running the two programs to make scattering tables, and a list of files in the distribution.

SHDOMPP and SHDOMPPDA Distributions

The models are distributed via this Web page. SHDOMPP and the forward model of SHDOMPPDA are freely distributed. The source files for the SHDOMPPDA tangent linear (shdomppda_ftls.f90) and the adjoint (shdomppda_ads.f90) cannot be freely distributed due to licensing requirements by FASTOPT, the owner of the TAF compiler used to produce these files. Dummy routines are distributed instead. If the tangent linear or adjoint is needed, please request permission from, and then contact me ( with evidence of this permission, so I can email the files to you.

SHDOMPP and SHDOMPPDA are distributed as a gzipped Unix tar files. Each distribution contains a documentation file, Fortran 90 source code and a makefile, and example scripts and data files that illustrate using the models. SHDOMPPDA is meant to be used by calling the Fortran subroutines in the shdomppda_fwd_tl_adj module, but an example program is included.

The SHDOMPP distribution is 275kB.

The SHDOMPPDA distribution is 903 kB.

Get yang2005_ice_scatter.db (16 MB) for making SHDOMPPDA ice crystal scattering tables.

Last modified: July 16, 2008

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