On the two-day oscillations and the day-to-day variability in global 3-D-modeling of the chemical system of the upper mesosphere/mesopause region

Abstract

Abstract. The integration of the photochemical system of the upper mesosphere/mesopause region brought evidence that the system is able to respond in a nonlinear manner under certain conditions. Under the action of the diurnallyperiodic insolation, the system creates subharmonic oscillations or chaos if disregarding strong diffusion, and under special conditions it possesses multiple solutions. The models used in the past were simplified and idealized in view of the number of dimensions and the consideration of the full dynamics. On the basis of our global 3-D-model of the dynamics and chemistry of the middle atmosphere (COMMA-IAP), we also found a nonlinear response in the photochemistry under realistic conditions. The model under consideration is not yet self-consistent, but the chemical model uses the dynamical fields calculated by the dynamic model. From our calculations we got period-2 oscillations of the photochemical system within confined latitudinal regions around the solstices but not during the equinoxes. The consequence of the period-2 oscillation of the chemical active minor constituents is that a marked two-day variation of the chemical heating rates is an important thermal pumping mechanism. We discuss these findings particularly in terms of the influence of realistic dynamics on the creation of nonlinear effects.

Short‐period solar cycle signals in the ionosphere observed by FORMOSAT‐3/COSMIC

“…Notable examples include the 2‐day oscillation in O 3 , temperature and water vapor observed in the mesosphere [ Azeem et al , 2001; Limpasuvan and Wu , 2003]. In these cases the solar forcing is at 1‐day, but a nonlinear response of the atmosphere could result in a 2‐day oscillation, as demonstrated in a simple but realistic model of the upper atmosphere [ Sonnemann and Grygalashvyly , 2005].…”

Theoretical investigation of the influence of a quasi‐2‐day wave on nonlinear photochemical oscillations in the mesopause region

“…In addition, our model takes into account the dependence of the photodissociation coefficients of H 2 O, O 3 , and O 2 on height and local zenith angle of the Sun (courtesy of G. R. Sonnemann). Dependence of local zenith angle on local time and latitude are calculated by a standard procedure (like, for example, in the COMMA‐IAP model [ Sonnemann and Grygalashvyly , 2005]). In sections 5–6 we will present our results obtained for latitude 40°S.…”

“…As these oscillations and the QTDW have almost the same timescale, the action of the QTDW on the region of nonlinear response can be expected to lead to more pronounced variability in the dynamics of minor gas constituents in this region than outside it. In addition, the corresponding photochemical heating at the 2‐day harmonic is quite noticeable (up to 2 K day −1 [ Sonnemann and Grygalashvyly , 2005]). Consequently, if the wave and photochemistry are in spatial resonance, the effect of the heating may be significant, at least in temperature oscillations in the QTDW.…”

Wave mixing effects on minor chemical constituents in the MLT region: Results from a global CTM driven by high-resolution dynamics

“…Another argument for the necessity of 3D simulations when studying the interaction of GWs and photochemical processes derives from the fact that the MLT can be considered as a nonlinear chemical oscillator enforced by the diurnal cycle of solar insolation [ Sonnemann and Fichtelmann , 1987; Fichtelmann and Sonnemann , 1987, 1992]. This system is able to produce chemical resonances, subharmonic oscillations, and chaotic attractors [ Sonnemann and Fichtelmann , 1997; Sonnemann , 2001; Sonnemann and Grygalashvyly , 2003, 2005], all of which requires 3D dynamics for a theoretical description. The influence of turbulent diffusion on the nonlinear behavior of the photochemical system was investigated by means of sensitivity studies, showing a complicated model response when using the diffusion coefficient as a control parameter [ Sonnemann and Feigin , 1999a, 1999b; Sonnemann et al , 1999].…”