Solar cycle and stratospheric ozone Geoscientific Instrumentation Methods and Data Systems Stratospheric O 3 changes during 2001–2010: the small role of solar flux variations in a CTM Solar cycle and stratospheric ozone

Abstract

Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Ex-periment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some mod-elling studies have suggested that stratospheric/lower mesospheric O 3 changes during 5 solar cycle 23 (1996–2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O 3 using three different solar flux datasets (SORCE, NRL-SSI and SATIRE-S). Simulated O 3 changes are compared with Microwave Limb Sounder (MLS) 10 and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O 3 anomalies from all solar flux datasets show good agree-ment with the observations, despite the different flux variations. The off-line CTM re-produces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle 15 stratosphere due to changes in stratospheric dynamics. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux datasets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O 3 changes during 2001–2010.