Line-by-line radiative excitation model for the non-equilibrium atmosphere: Application to CO[sub 2] 15-[mu]m emission

Journal Article · Fri Nov 20 04:00:00 EST 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JD01494· OSTI ID:7066233

Wintersteiner, P P ^[1]; Picard, R H; Sharma, R D; Winick, J R ^[2]

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1. ARCON Corp., Waltham, MA (United States)
2. Hanscom Air Force Base, MA (United States)

We describe a new line-by-line (LBL) algorithm for radiative excitation in infrared bands in a non-local thermodynamic equilibrium (non-LTE) planetary atmosphere. Specifically, we present a predictive model for the terrestrial CO[sub 2] 15[mu]m emission that incorporates this generic algorithm, and validate the model by comparing its results with emission spectra obtained in a limb-scanning rocket experiment. The unique features of the reactive-excitation algorithm are discussed in this paper. These features contribute to accurate radiative transfer results and reliable atmospheric cooling rates. For altitudes above 40 km, we present results of model calculations of CO[sub 2]([nu][sub 2]) vibrational temperatures, 15-[mu]m limb spectral radiances, and cooling rates, for the main band and for weaker hot and isotopic bands. We calculate the excitation and deexcitation rates due to different processes. We compare the predicted limb radiance with earthlimb spectral scans obtained in the SPIRE rocket experiment over Poker Flat, Alaska, and get excellent agreement as a function of both wavelength and tangent height. This constitutes the first validation of a long-wavelength CO[sub 2] non-LTE emission model using an actual atmospheric data set and verifies the existence of certain aeronomic features that have only been predicted by models and constrains the previously unknown value of the very important rate constant for deactivation of the CO[sub 2] bending mode by atomic oxygen to the range of 5-6 [times] 10[sup [minus]12] cm[sup 3]/(mol s) at mesospheric and lower thermospheric temperatures. We discuss the significance of this large value for terrestrial and Venusian thermospheres and the convergence rate of the iterative scheme, the model's sensitivity to the background atmosphere, the importance of the lower boundary surface contribution, and the effects of the choice of the layer thickness and the neglect of line overlap. 86 refs., 20 figs., 5 tabs.

• OSTI ID: 7066233
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 97:D16; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

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54 ENVIRONMENTAL SCIENCES
540110*
ALASKA
ALGORITHMS
ATMOSPHERES
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CHALCOGENIDES
DEVELOPED COUNTRIES
EARTH ATMOSPHERE
EMISSION SPECTRA
EQUATIONS
MATHEMATICAL LOGIC
MATHEMATICAL MODELS
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
PLANETARY ATMOSPHERES
PREDICTION EQUATIONS
SPECTRA
TESTING
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VALIDATION