Ozone and Temperature Responses to the Short-term Solar Ultraviolet Flux Variability in a Coupled Model of Photochemistry and Dynamics

The short-term solar UV flux variability will produce direct and indirect responses on the atmospheric states. The direct response is defined as the localized changes in the atmospheric state caused by the in situ absorption of the solar UV radiation and the indirect response is the non-localized changes resulting from transport that couples photochemistry with dynamics. By consistently including both the thermal and photochemical effects of the solar 27-day UV flux variability in the JHU/APL 2D coupled model we derive ozone and temperature responses in the upper mesosphere that are consistent with measurements. The sensitivity studies show that the ozone response is primarily due to localized photochemistry whereas the temperature response is mostly induced by the meridional circulation. A distinct feature of the direct response in chemical species is the strong local-time dependence of the sensitivity in tracer distributions (including ozone) forced by the 27-day cycle solar UV flux variability. On the other hand, the response of the temperature perturbation has a seasonal variation that is correlated to the strength of the meridional circulation.