The HAMMONIA Chemistry Climate Model: Sensitivity of the Mesopause Region to the 11-year Solar Cycle and CO2 Doubling

This paper introduces the three-dimensional Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) that treats atmospheric dynamics, radiation and chemistry interactively for the height range from the Earth’s surface to the thermosphere (approximately 250 km). It is based on the latest version of the ECHAM atmospheric general circulation model of the Max Planck Institute for Meteorology in Hamburg, which is extended to include important radiative and dynamical processes of the upper atmosphere and coupled to a chemistry module containing 48 compounds. The model is applied to study the effects of natural and anthropogenic climate forcing on the atmosphere, represented on the one hand by the 11-year solar cycle and on the other hand by a doubling of the present-day concentration of carbon dioxide. The numerical experiments are analyzed with the focus on the effects on temperature and chemical composition in the mesopause region. Results include a temperature response to the solar cycle by 2 to 10 K in the mesopause region with the largest values occurring slightly above the summer mesopause. Ozone in the secondary maximum increases by up to 20% for solar maximum conditions. Changes in winds are in general small. In the case of a doubling of carbon dioxide the simulation indicates a cooling of the atmosphere everywhere above the tropopause but by the smallest values around the mesopause. It is shown that the temperature response up to the mesopause is strongly influenced by changes in dynamics. During northern hemisphere summer, dynamical processes alone would lead to an almost global warming of up to 3 K in the uppermost mesosphere. Max Planck Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany, [email protected] Meteorological Service of Canada, Dorval, Canada National Institute for Geophysics and Volcanology, Bologna, Italy GEST/UMBC, NASA Goddard Space Flight Center, Greenbelt MD, USA