Effect of temperature-dependent cross sections on O₄slant column density estimation by a space-borne UV–visible hyperspectral sensor

The sensitivities of oxygen dimer (O₄) slant column densities (SCDs) were examined by applying temperature-dependent O₄cross sections using the radiative transfer model (RTM) calculation with the linearized pseudo-spherical vector discrete ordinate radiative transfer model. For the sensitivity study, we used a newly developed cross section database in place of the database used in the operational algorithm. Newly investigated O₄cross section databases for 203 K and 293 K were used for the radiance simulation by interpolating temperature for each atmospheric layer based on the vertical profile of standard atmosphere in the RTM. The effect of the temperature-dependent cross sections was a significant O₄SCD increase of 8.3% with dependence on satellite and solar viewing geometries. Furthermore, the O₄SCD generally increased by an estimated 3.9% based on the observation geometries of the Ozone Monitoring Instrument. For the long-term comparison, the O₄SCD estimated from the temperature-dependent cross sections corrects 20% of the total underestimation of O₄SCD between the observation and simulation. Although the surface pressure variation and background aerosol effect also correct the O₄SCD discrepancy, the effect of temperature-dependent cross sections was more important than the effects of surface pressure variation and background aerosols. Therefore, temperature dependence of the cross section in the RTM calculation is essential for the accurate simulation of O₄SCD.