On the influence of diffusion upon the nonlinear behavior of the photochemistry of the mesopause region

Abstract

Abstract. The photochemical system of the mesopause region is a nonlinear driven oscillator enforced by the diurnal-periodic solar radiation. Under idealized conditions this oscillator can display nonlinear effects such as period doubling cascades or chaos. We investigate what happens if this system is subjected to atmospheric diffusion. A highresolution one-dimensional chemical system of the mesopause region has been established in order to answer this question. Strong diffusion destroys nonlinear effects, but for the lower values of the diffusion coefficient which are still of the order of magnitude of real values, different nonlinear effects occur. The most important effect consisted of the creation of a 2-day subharmonic oscillation. Such a 2-day oscillation of the concentration of chemical active species entails a corresponding oscillation of the chemical heating rates which feeds back to the dynamics of this region. The zonal wind influences the period of the oscillation so that the periods differ from the exact 48-hour value by a few hours depending on the wind velocity and its direction. We call this phenomenon the photochemical Doppler effect. IntroductionThe mesopause region is one of the most interesting and most important regions of the upper atmosphere. Above this region, within the thermosphere, the variations caused by the alteration of the extraterrestrial solar shortwave spectrum (EUV and X ray) and particle precipitation dominate. Below this layer the meteorological influences predominantly deter-

Several notes on the OH* layer

“…(21) points to the possible bi-stable behavior of the OH * layer peak. Realistic modeling at different parameters (e.g., water vapor, vertical eddy diffusion coefficient) related to the mesopause conditions infers period 2 oscillations that trigger 2-day variations in odd-oxygen / odd-hydrogen concentrations (Fichtelmann and Sonnemann, 1992;Sonnemann and Fichtelmann, 1997;Sonnemann and Feigin, 1999a, b;Sonnemann et al, 1999). Often, airglow measurements infer 2-day oscillations in the temperature and wind data in the mesopause region (e.g., Ward et al, 1996;Takahashi et al, 2005;López-González et al, 2009;Pedatella and Forbes, 2012, and references therein).…”

The mechanism of non-linear photochemical oscillations in the mesopause region

“…The analysis of the influence of vertical eddy diffusion on MPCS evolution performed by Sonnemann and Feigin (1999) and Sonnemann et al (1999) revealed that transport reduces appreciably the spectrum of possible modes of behavior of this system. It was found that for the values of the vertical diffusion coefficient (5-20) m 2 s −1 observed in the mesopause region in summer (e.g.…”

“…These parameters, in turn, depend on altitude. In the works by Sonnemann et al (1999) and Sonnemann and Feigin (1999), it was demonstrated that it is sufficient to take this dependence into consideration in the mesopause region only for the air concentration and photolysis rate of molecular oxygen.…”

“…Besides, the interest in nonlinear oscillations in the mesopause region is associated with the fact that they may influence the behavior of key characteristics of the mesosphere. The point is that exothermal reactions between the chemical constituents of the mesospheric photochemical system ensure the main photochemical heating of the mesospheric air (and the rate of the heat influx caused by these processes) reaches 1-2 K per day at the heights of the nonlinear-response region (Sonnemann et al, 1999). Therefore, nontrivial behavior of minor gas constituents can manifest noticeably in the variability of air temperature in the upper mesosphere and, consequently, in variations of other characteristics of this region.…”

“…Further studies of the nonlinear response of mesospheric photochemistry (Sonnemann et al, 1999;Sonnemann and Feigin, 1999;Sonnemann, 2001;Feigin, 2004, 2005;Kulikov, , 2007Sonnemann and Grygalashvyly, 2005;Kulikov and Gashturi, 2006) revealed that behavior of the concentrations of minor gas constituents may be simpler…”