SHARC, A Model for Calculating Atmospheric and Infrared Radiation Under Non-Equilibrium Conditions

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. Comprehensive coverage of the 2 to 40 microns (250/cm to 5,000/cm) wavelength region is provided for arbitrary lines...

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Bibliographic Details
Main Authors: Sundberg, R L, Duff, J W, Gruninger, J H, Bernstein, L S, Sharma, R D
Format: Report
Language:English
Subjects:
AIR FORCE
ALGORITHMS
ALTITUDE
ATMOSPHERE MODELS
ATMOSPHERES
Atmospheric Physics
ATMOSPHERIC TEMPERATURE
ATMOSPHERICS
AURORAE
COMPARISON
Computer Programming and Software
COMPUTER PROGRAMS
ENERGY TRANSFER
EQUILIBRIUM(GENERAL)
EXCITATION
HIGH ALTITUDE
INFRARED RADIATION
INFRARED SPECTRA
Meteorology
MOLECULAR STATES
Optics
RADIANCE
RADIATIVE TRANSFER
REACTION KINETICS
SHARC COMPUTER PROGRAM
SPECTRA
THERMODYNAMIC EQUILIBRIUM
THERMODYNAMICS
TRANSMITTANCE
VIBRATION
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Summary: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. Comprehensive coverage of the 2 to 40 microns (250/cm to 5,000/cm) 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 process 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. This 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 CO2, 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. Non-local thermodynamic equilibrium, Infrared radiation, Computer code, Vibrational and rotational levels, Limb radiance.