Effect of long‐term solar variability in a two‐dimensional interactive model of the middle atmosphere

Abstract

An assessment of the influence of long‐term solar variability on the climatology of the middle atmosphere is made using a two‐dimensional model incorporating interactive chemistry, radiation, and dynamics. The primary motivation behind this work is the more updated measurements of the solar flux variation and the more comprehensive treatment of the chemical and physical processes in the two‐dimensional model. Despite various feedback mechanisms inherent to the model, imposing a solar flux variation in the two‐dimensional model does not create any substantial response in the stratosphere. Since the largest changes in the solar flux occur in wavelengths shorter than 200 nm, the most obvious effect of solar variability is above the altitude of 60 km. In general, the response of the middle atmosphere to long‐term solar variability predicted by the two‐dimensional model is substantially weaker than those predicted by previous model studies, which is primarily a result of the smaller solar flux variation adopted in this study. Compared with recent data analyses, the calculated response of ozone and temperature near the tropical stratopause and the calculated zonal‐wind response at midlatitude upper stratosphere are much weaker. In addition, the anticorrelated temperature and ozone response at 70 km seen in observational analyses for short‐term solar variability cannot be simulated by the model, albeit for long‐term solar variability simulations. These suggest that the physical and chemical processes and their feedback effects in the middle atmosphere are not yet fully understood.