Comparison of air mass computations

Knowledge of air mass is vital for the interpretation of twilight measurements of trace gases, as well as the conversion of measured slant column amounts to vertical abundances for comparison with model predictions. Radiative transfer computations were used to determine NO2 air mass values for clear skies at 450 and 650 nm using a discrete ordinate (two different formulations), Monte Carlo, and an integral equation method. All four methods yielded agreement to within 6% at a solar zenith angle of 90° when the absorber was located in the stratosphere. For a tropospheric absorber, differences as large as 21% occurred at 90°. Since only the Monte Carlo method treats the scattered radiation in spherical geometry, it is more accurate for computing tropospheric air masses where multiple scattering is significant. The other three models use a conceptual approximation by treating the scattered radiation in plane parallel geometry. However, for absorbers in the stratosphere, major saving of computing time without any loss of accuracy is obtained using the discrete ordinate or integral equation method as compared to the Monte Carlo method.

[1]  M. V. Roozendael,et al.  Ozone and NO2 air‐mass factors for zenith‐sky spectrometers: Intercomparison of calculations with different radiative transfer models , 1995 .

[2]  A. Dahlback,et al.  Effects of stratospheric aerosols from the Mt. Pinatubo eruption on ozone measurements at Sodankylä, Finland in 1991/92 , 1994 .

[3]  P. Hughes,et al.  Depletions in winter total ozone values over southern England , 1994 .

[4]  Stanley C. Solomon,et al.  On the evaluation of air mass factors for atmospheric near‐ultraviolet and visible absorption spectroscopy , 1993 .

[5]  Lori M. Perliski,et al.  Radiative influences of pinatubo volcanic aerosols on twilight observations of NO2 column abundances , 1992 .

[6]  R. McKenzie,et al.  Observations of depleted stratospheric NO2 following the Pinatubo volcanic eruption , 1992 .

[7]  Lori M. Perliski.  The Role of Multiple Scattering in Twilight Zenith Sky Observations of Atmospheric Absorbers: Diurnal Photochemistry and Airmass Factors , 1992 .

[8]  Arvekylling,et al.  Efficient yet Accurate Solution of the Linear Transport Equation in in the Presence of Internal Sources: The Exponential-Linear-in-Depth Approximation , 1992 .

[9]  James B. Kerr,et al.  Altitude distributions of stratospheric constituents from ground‐based measurements at twilight , 1991 .

[10]  K. Stamnes,et al.  A new spherical model for computing the radiation field available for photolysis and heating at twilight , 1991 .

[11]  S. Lloyd,et al.  Polar twilight UV-visible radiation field: Perturbations due to multiple scattering, ozone depletion, stratospheric clouds, and surface albedo , 1990 .

[12]  H. Dorn,et al.  Near UV atmospheric absorption measurements of column abundances during Airborne Arctic Stratospheric Expedition, January – February 1989: 1. Technique and NO2 observations , 1990 .

[13]  S. Solomon,et al.  Visible and near‐ultraviolet spectroscopy at McMurdo Station, Antarctica: 5. Observations of the diurnal variations of BrO and OClO , 1989 .

[14]  F. Goutail,et al.  Stratospheric O3 and NO2 observations at the southern polar circle in summer and fall 1988 , 1988 .

[15]  K. Stamnes,et al.  Numerically stable algorithm for discrete-ordinate-method radiative transfer in multiple scattering and emitting layered media. , 1988, Applied optics.

[16]  Stanley C. Solomon,et al.  Visible spectroscopy at McMurdo Station, Antarctica , 1987 .

[17]  R. McKenzie,et al.  Seasonal variations in stratospheric NO2 at 45°S , 1982 .

[18]  A. W. Harrison.  Midsummer stratospheric NO2 at latitude 45°S , 1979 .

[19]  George W. Kattawar,et al.  Radiative transfer in spherical shell atmospheres: I. Rayleigh scattering , 1978 .

[20]  G. Kattawar,et al.  Radiative transfer in spherical shell atmospheres: II. Asymmetric phase functions , 1977 .

[21]  C. Oldham.  Self-reliant development , 1976, Nature.

[22]  J. Noxon,et al.  Nitrogen Dioxide in the Stratosphere and Troposphere Measured by Ground-Based Absorption Spectroscopy , 1975, Science.

[23]  J. Kerr,et al.  Nitrogen Dioxide Concentrations in the Atmosphere , 1973, Nature.

[24]  D. Collins,et al.  Backward monte carlo calculations of the polarization characteristics of the radiation emerging from spherical-shell atmospheres. , 1972, Applied optics.

[25]  R. Kalaba,et al.  Radiative Transfer in Spherical Shell Atmospheres with Radial Symmetry , 1971 .