Solar variability and minor constituents in the lower thermosphere and in the mesosphere

Space Science Reviews - The variation in the solar irradiance related for example to the 11-year cycle leads to changes in the photodissociation and photo-ionization of the upper and middle...     

The Response of the Middle Atmosphere to Solar Cycle Forcing in the Hamburg Model of the Neutral and Ionized Atmosphere

This paper studies the response of the middle atmosphere to the 11-year solar cycle. The study is based on numerical simulations with the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA), a chemistry climate model that resolves the atmosphere from the Earth’s surface up to about 250 km. Results presented here are obtained in two multi-year time-slice runs for solar maximum and minimum conditions, respectively. The magnitude of the simulated annual and zonal mean stratospheric response in temperature and ozone corresponds well to observations. The dynamical model response is studied for northern hemisphere winter. Here, the zonal mean wind change differs substantially from observations. The statistical significance of the model’s dynamical response is, however, poor for most regions of the atmosphere. Finally, we discuss several issues that render the evaluation of model results with available analyses of observational data of the stratosphere and mesosphere difficult. This includes the possibility that the atmospheric response to solar variability may depend strongly on longitude.     

Hemispheric asymmetry of chemical species and its effect on stratospheric ozone: Emphasis on halogen loading

Differences between the dynamical characteristics of the northern hemisphere (NH) and southern hemisphere (SH) stratosphere (e.g., the temperature, the strength of polar vortex, and the mean meridional circulation) produce hemispherically asymmetrical distributions of chemical species. In this paper, we use global models to briefly discuss various effects on chemical species caused by this asymmetrical distribution, especially on stratospheric ozone. The role of hemispheric asymmetries in chlorine and bromine loadings on mid- and high latitude ozone depletion is particularly discussed.