Solar variability plays an important role in influencing the Earth's climate system. Accurate quantification of the response of stratospheric ozone and temperature to the 11-year solar cycle signal (SCS) is important in understanding global climate change. However, estimates of a realistic solar cycle signal are challenging due to their sensitivity to the quality of the observational datasets, the statistical methodologies as well as the non-linear coupling and complex changes in forcing processes.
Here, we use the Microwave Limb Sounder (MLS) ozone profile measurements from 2005-2020 to estimate the 11-year SCS in stratospheric ozone. Additionally, we also analyse output from a chemical transport model (TOMCAT- CTM) simulation (forced with ECMWF ERA5 reanalysis) and the MERRA-2 Stratospheric Composition Reanalysis of Aura Microwave Limb Sounder (M2-SCREAM). We use multivariate linear regression (MLR) models based on ordinary least squares (OLS) and regularised (ridge) approach to estimate the ozone and temperature SCS. The regression coefficients from both OLS and ridge models, including the quasi-biennial oscillation, solar variability, El Niño-Southern Oscillation, Arctic oscillation, Antarctic oscillation, and Eliassen-Palm flux, represent the ozone and temperature variations associated with natural processes.
We find that SCS derived using TOMCAT and M2-SCREAM data is consistent with MLS, except that TOMCAT overestimates the SCS in the lower stratosphere. There is an evident seasonal dependence in the ozone and temperature SCS profiles. Both OLS- and ridge-based ozone SCS show a double-peaked structure with primary peak near 5 hPa and secondary peak near 70 hPa. Ridge-based SCS yields smaller coefficients due to correlated explanatory variables. Significant differences between OLS- and ridge-based ozone SCS appear in the tropical mid-stratosphere and extra-tropics of the northern hemisphere, indicate how different settings in SCS using MLR models estimates play a role in the appearance of the solar cycle response.

stratospheric ozone,stratospheric temperature,solar cycle