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This supplement lists the LOWTRAN 6 computer code for predicting atmospheric transmittance and the thermal radiation emitted by the atmosphere and earth from 350 to 40,000 per cm at a spectral resolution of 20 per cm. The program is based on the LOWTRAN 5 (1980) computer code. Solar/lunar scattered radiation has ben added to the code, as well as a new spherical refractive geometry subroutine and an improved water vapor continuum model. Other modifications to the code include a wind-dependent maritime aerosol model, a vertical structure aerosol model, a cirrus cloud model, and a rain model. The computer code contains representative (geographical and seasonal) atmospheric models and representative aerosol models with an option to replace them with user-derived or measured values. The program can be run in one of three modes, namely, to compute only atmospheric transmittance, to compute atmospheric transmittance and radiance, or to compute atmospheric transmittance, atmospheric radiance, and scattered solar/lunar background radiance for a given slant path geometry. Two new programs now available with the LOWTRAN 6 package, the plot program and the filter function program, are listed in this supplement.
Calculations of atmospheric transmittance and radiance require the knowledge of the integrated amounts of the absorbing gases along the path. This report describes the calculation of the integrated amounts ('air mass' or 'column density') for various infrared absorbing gases for an arbitrary slant path through the atmosphere, including the effects of both curvature and refraction, and presents a Fortran program. FSCATM, to perform the calculation. Among the features of FSCATM are: 1. It calculates the layer-by-layer integrated absorber amounts and density-weighted pressure and temperature for an arbitrary slant path through the atmosphere. 2. It assumes a spherically symmetric atmospheric with exponential profiles of density and refractivity between layer boundaries. 3. It allows a variety of options for specifying the slant path. 4. It includes six representative atmospheric profiles of pressure and temperature, and of density for the gases H2O, CO2, O3, N2O, CO, CH3, and O2 and has provision for user-supplied profiles of up to 20 gases. 5. The output layering may either be generated internally or supplied by the user. 6. It portable to 32 bit word computers in single precision and compatible with both ANSI Standard FORTRAN 66 and 77. 7. It is modular and easily modified to suit the users' particular needs. A discussion of atmospheric profile data and a survey of the literature are included in appendices.
LOWTRAN 7 is a low-resolution propagation model and computer code for predicting atmospheric transmittance and background radiance from 0 to 50,000 cm -1 at a resolution of 20 cm -1. The code is based on the LOWTRAN 6 (1983) model. Multiple scattered radiation has been added to the model as well as new molecular band model parameters and new ozone and molecular oxygen absorption parameters for the UV. Other modifications include a wind dependent desert model, new cirrus cloud models, and new cloud and rain models. The code also includes new representative (geographical and seasonal) atmospheric models and updated aerosol models with options to replace them with user-derived values. An improved extra-terrestrial solar source function is also included. Six modes of program execution are allowed with the new model and computer code for a given slant path geometry. This report contains a description to users for operating the LOWTRAN 7 computer code. It summarizes the capabilities of the new code, provides complete operating instructions as well as input and output from test cases for user validation. Also included are operating instructions for three programs that utilize LOWTRAN 7 output (plot, filter and scanning function programs).