
Accession Number : ADA263213
Title : RADTRAN With SphericalRefractive Geometry.
Descriptive Note : Technical rept.,
Corporate Author : ATMOSPHERIC AND ENVIRONMENTAL RESEARCH INC CAMBRIDGE MA
Personal Author(s) : Gallery, William ; Isaacs, Ronald
Report Date : 22 DEC 1992
Pagination or Media Count : 39
Abstract : RADTRAN is a model and computer program for computing atmospheric transmittance and radiance in the microwave region. The previous version of RADTRAN assumed a plane parallel nonrefracting atmosphere for computing the amounts of absorbers and scatterers (e.g. oxygen, water vapor, clouds, rain) along the optical path. However, the planeparallel assumption breaks down for zenith angles greater than about 80 degrees, leading to large errors in the calculated radiance and transmittance. The standard Phillips Lab atmospheric raytrace model FSCATM has been incorporated into RADTRAN as an option to calculate the absorber amounts. FSCATM uses spherical. refractive geometry to compute the layerbylayer absorber amounts and densityweighted pressure and temperature for any slant path through the atmosphere. The atmospheric profiles from RADTRAN are retained. In the new program, called RADTRANS, the sphericalrefractive geometry is available as an option, otherwise the program retains all the capabilities of the original version. However, the spherical geometry is incompatible with the multiple scattering model so the multiple scattering calculations must still be run using the planeparallel geometry. Sample calculations are shown for the case of a satellite sensor scanning the nadir from 890 km. The radiance and the transmittance are calculated for 37, 90, and 150 GHz for both spherical and planeparallel geometries. The results show differences of up to 70 K in brightness temperature at 37 GHz out near the horizon.... Microwave Radiation, Air mass, Atmospheric radiation, Transmittance/radiance models.
Descriptors : *ATMOSPHERES, *COMPUTER PROGRAMS, *RADIANCE, *TRANSMITTANCE, ANGLES, ARTIFICIAL SATELLITES, ATMOSPHERICS, BRIGHTNESS, CLOUDS, COMPUTERS, DENSITY, ERRORS, GEOMETRY, HORIZON, LAYERS, MASS, MICROWAVES, MODELS, OXYGEN, PATHS, PRESSURE, PROFILES, RADIATION, RAIN, REGIONS, SCANNING, SCATTERING, STANDARDS, TEMPERATURE, VAPORS, WATER, WATER VAPOR.
Subject Categories : Computer Programming and Software
Atmospheric Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE