Assess the predictive accuracy of fixed-zenith-angle choices across atmospheric states

Determine whether fixed solar-zenith-angle choices tuned to reproduce the mean ozone column remain predictive when one-dimensional photochemical models are applied to atmospheric states substantially different from the modern Earth.

Background

One-dimensional photochemical models commonly use a single fixed solar zenith angle to approximate planetary-average or diurnal photochemistry. The paper shows that changing this angle alters the predicted ozone column, so a value may be tuned to reproduce a particular mean state.

The authors state that the reliability of such tuning for paleo-atmospheres or exoplanet atmospheres with different climates and compositions is unresolved. This is important because fixed-zenith-angle approximations may introduce systematic errors when models are extrapolated beyond the modern Earth.

References

As demonstrated in our analyses, altering the zenith angle with standard boundaries changes the resulting \ce{O3} column. To achieve the average \ce{O3} column, a 1D model may require tuning of the fixed zenith angle. The predictive accuracy of these fine tuned zenith angle choices when applied to vastly different atmospheric states is currently unknown.

— Simulations of the Evolving Ozone Layer: Implications for the Early Earth, Exoplanets, and the Search For Life  (2610.18864 - Kumar et al., 13 Oct 2026) in Section 5.1, “3D effects for Earth’s O3”