The Solar Signal in OSIRIS Ozone and Aerosol Measurements

Abstract

The intensity of solar radiation reaching the Earth’s atmosphere varies over the 25 to 35 day solar rotation period and the 11 year solar cycle. Tropical ozone and aerosol profiles from the Optical Spectrograph and InfraRed Imager System (OSIRIS) are used to investigate the effect of changes in solar ultraviolet flux on stratospheric ozone concentrations and aerosol extinction levels from 2002 to 2015. This time range covers the end of solar cycle 23 and the beginning of solar cycle 24. A solar rotation signal in the OSIRIS ozone time series is observed above 40 km. The maximum correlation between ozone and solar flux is 0.33 during solar cycle 23 and 0.15 during solar cycle 24. Results from solar cycle 23 were consistent with those from other instruments, confirming the validity of using OSIRIS data to study the effect of solar rotation on stratospheric ozone. This provides a larger data set and insight into the relatively weak solar cycle 24 that can be used in future climate modelling. A clear effect of solar UV irradiance on OSIRIS aerosol extinction levels was not found. Galactic cosmic rays (GCRs) are thought to affect the aerosol extinction level and aerosol particle size by ionizing the atmosphere to produce more and smaller particles. The effect of GCRs on OSIRIS aerosol parameters was considered by looking at the effect of sudden decreases in the GCRs measured at the Earth called Forbush decreases (FDs). A significant response in the aerosol data to FDs was not observed.