Middle Atmosphere Response to Solar Ultraviolet Radiation Variation

The solar ultraviolet radiation induced variations in the middle atmosphere are of great interest because they are connected to changes in ozone and temperature through radiative-chemical-dynamical coupling in the stratosphere and mesosphere. Understanding the processes that control the naturally-induced changes are specially important for our ongoing study and predictive capability of human-induced changes. The middle atmosphere response to short-term and long-term solar radiation variations thus has been pursued for many decades. Significant progress has been made as long-term satellite observations of radiatively important species and temperatures became available, resulting in the successful development of many multi-dimensional theoretical models that have been used for studying middle atmosphere variability and predicting human-induced changes. Most recently, the NASA TIMED mission has collected middle atmosphere composition and temperature data for almost one solar cycle. This data set provides a great opportunity for us to test these models and verify our understanding of coupling processes. The challenge, however, is the proper interpretation of TIMED observations, which are complicated by their spatial and temporal aliasing (i.e. separation of tides and zonal mean). This paper will summarize the data analysis challenge we face, its impact on our study of short-term solar-induced variations, and introduce a data analysis scheme to accurately quantify the middle atmosphere sensitivity to solar UV radiation. We will present the sensitivity results based on TIMED observations and compare them with previous findings and theoretical model predictions. The uniqueness of this analysis scheme and the future studies enabled will be discussed.