Non-linear behaviour in the photochemistry of minor constituents in the upper mesosphere

Abstract

Resonance effects or nonlinear behavior of the density of minor constituents for certain conditions are studied using a simplified model of the photochemistry of the upper mesosphere and the mesopause. The photochemical system is considered as an oscillator operating in the vicinity of resonance. Under sufficiently loss-free conditions the system exhibits typical nonlinear oscillations. Photochemical resonances, period doubling cascades, chaotic orbits, and intermittances are found. The system is strongly influenced by humidity. The relatively large variation of water vapor densities found in measurements may move the real photochemical system into ranges of nonlinear behavior. Since chemical heating is the dominant energy source in the mesopause region, particularly in summer, it may be a stimulating force of the quasi-2-day prevailing wind variations discovered by Mueller (1972).