Calculated upper stratospheric effects of solar UV flux and NOy variationsduring the 11-year solar cycle

Model derived sensitivities of O-3 near 40 km to solar UV flux changes (11- year and 27-day) fall within the range 0.36 - 0.55 with S-11y approximate t oS(27d). These sensitivities derived from observations have been reported t o be 0.91 and 0.39 - 0.46, respectively. This discrepancy appears to be due to long-term (2-10 years) fluctuations in stratospheric NO2 in the 1980s. Such fluctuations, if not taken into account in the analysis of the date, c ould lead to high values of the sensitivity for the 11-year activity cycle but not for the 27-day solar rotation period. Simulations accounting for su ch effects suggest a consistency between theoretical values of S-11y and th ose derived from data if NO2 effects are included. The appropriate values a re approximately 0.48, a value similar to published model calculations and results from the analysis of data from the 27-day solar rotation period. Ve rification of this suggestion awaits an NO2 data, base of sufficient qualit y and length to permit solar-cycle trend calculations to be made.