| SHARC, A Model for Calculating Atmospheric and Infrared Radiation Under Non-Equilibrium Conditions, (1994) | |||||||||
Abstract | |||||||||
| A new computer model, SHARC, has been developed by the Air Force for calculating high-altitude atmospheric IR radiance and transmittance spectra with a resolution of better than 1 cm to the -1 power. Comprehensive coverage of the 2 to 40 micrometer (250 to 5000 cm to the -1 power) wavelength region is provided for arbitrary lines of sight in the 50-300 km altitude regime. SHARC accounts for the deviation from local thermodynamic equilibrium (LTE) in vibrational state populations by explicitly modeling the detailed production, loss, and energy transfer processes among the important molecular vibrational states. The calculated vibrational populations are found to be similar to those obtained from other non-LTE codes. The radiation transport algorithm is based on a single-line equivalent width approximation along with a statistical correction for line overlap. The approach is reasonably accurate for most applications and is roughly two orders of magnitude faster than the traditional LBL methods which explicitly integrate over individual line shapes. In addition to quiescent atmospheric processes, this model calculates the auroral production and excitation of COsub2, NO, and NO(+) in localized regions of the atmosphere. Illustrative comparisons of SHARC predictions to other models and to data from the CIRRIS, SPIRE and FWI field experiments are presented. | |||||||||
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