Null Variance Altitudes for the photolysis rate constants of species with barometric distribution: Illustration on Titan upper atmosphere modeling

► Influence of uncertain photolysis cross-section depends strongly on altitude. ► Uncertainty of photolysis rates is shown to cancel at specific altitudes. ► “Null Variance Altitudes” are those where the photolysis rates are maximal. ► This occurs for barometrically-distributed species (N2, CH4 in Titan's atmosphere).