Photodissociation rates and middle atmosphere photochemistry modeling

Several different parameterizations of photodissociation based on different datasets of solar irradiance have been used in modeling the photochemistry of the mesosphere and lower thermosphere and its response to solar activity. TIMED/SEE provides irradiance data critical for our understanding of middle atmosphere photochemistry over the entire declining phase of a solar cycle. In this paper we use the JHU/APL two- dimensional photochemistry and transport model to examine the sensitivity of modeled MLT composition (e.g., Ox and HOx) to the rates of O2 and H2O photodissociation by Lyman-alpha and the Schumann--Runge bands and continuum commonly used today and those based on TIMED/SEE measurements. The effects of solar cycle variability are also reported.