SUBGROUP A: MODELING OF THE NONEQUILIBRIUM POPULATIONS OF THE VIBRATIONAL STATES OF MOLECULES

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Intercomparison of the non-LTE population models is logically splitted in two parts:

1. Intercomparison of calculation algorithms and methods in case when the mechanisms driving non-LTE processes are known sufficiently well. This substudy is first of all concerned to solution of the radiative transfer equations by different methods.

   Proposed exercise:

   First step: CO2 15 µm band.

   Atmospheric model:
   Kinetic temperature, N2, O2, and atomic oxygen: MSISE90 generated for day, night, midlatitude winter/summer.

   CO2: "ROCKET", "GRILLE" and "MODEL" profiles - see Fig.9 on page 20489 of the paper [Rinsland et al., "Middle and upper atmosphere pressure-temperature profiles and the abundances of CO2 and CO in the upper atmosphere from ATMOS/Spacelab3 observations", JGR, Vol.97, No D18, pp. 20479-20495]

   Mechanisms of vibrational excitation and quenching, rate constants, number of vibrational states are given: Potential participants are requested to propose a self- consistent data set for the discussion to be open.

   This part of work should be done for 15 µm band CO2 since corresponding model is rather well developed:

   • vibrational levels under considerations
   • spectroscopic data
   • physical prosesses of excitation and quenching
   • rate constants of inelastic collisions
   • nonthermal excitation processes

   Main goals:

   • Comparison of the results of calculations for reference conditions and analysis of the reasons of discrepancies.
   • Correction of algorithms and their unification.
   • Formulation of the most important problems and requirements for the purpose of increasing the accuracy.

2. Intercomparison of population models in case when mechanisms driving non-LTE and rate constants are to a great extent uncertain.

   In principle, this part of work is applicable to a large number of molecules and bands. However due to the increased interest of scientific and public community to the ozone distribution in the middle atmosphere, the worked is focused on the ozone molecule.

   Proposed exercise:

   O3 4.8 µm and 9.6 µm band

   Atmospheric model:
   Kinetic temperature, N2, O2, and atomic oxygen: MSISE90 generated for day, night, midlatitude winter/summer.

   O3: AFGL model profiles midlatitude winter/summer [G.P.Anderson et al., AFGL Atmospheric Constituent Profiles (0-120km). AFGL-TR-86-0110, Environmental research papers, No 954, 1986, 43p.]

   Potential participants are requested to propose atomic oxygen profiles for extreme cases.

   Participants are supposed to use different mechanisms of vibrational excitation and quenching, different rate constants.

   Main goals:
   • Determination of the range of uncertainties
   • Analysis of the reasons of discrepancies.
   • Formulation of the most important problems and requirements for atmospheric and laboratory measurements.