Assessment of ACE-MAESTRO v3.13 multi-wavelength stratospheric aerosol extinction measurements

Abstract. The Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (MAESTRO) instrument on the SCISAT satellite provides aerosol extinction measurements in multiple solar wavelength bands. In this study, we evaluate the quality and utility of MAESTRO version 3.13 stratospheric aerosol extinction retrievals, from February 2004–February 2021, through comparison with measurements from other satellite instruments. Despite significant scatter in the MAESTRO data, we find that gridded median MAESTRO aerosol extinctions and stratospheric aerosol optical depth (SAOD) values are generally in good agreement with those from other instruments during volcanically quiescent periods. After volcanic eruptions and wildfire injections, gridded median MAESTRO extinction and SAOD are well-correlated with other measurement sets, but generally biased low by 40–80 %. The Ångström exponent (AE), which can provide information on aerosol particle size, is derived from the MAESTRO spectral extinction measurements in the lowermost stratosphere, showing perturbations after volcanic eruptions qualitatively similar to SAGE III for the eruptions of Ambae (2018) and Uluwan (2019). Differences in AE anomalies after the 2019 extratropical Raikoke eruption may be due to the different spatiotemporal sampling of the two instruments. Furthermore, we introduce a method to adjust MAESTRO extinction data based on comparison with extinction measurements from the Stratospheric Aerosol and Gas Experiment on the International Space Station (SAGE III/ISS) during the period from June 2017 to February 2021, resulting in improved comparison during volcanically active periods. Our work suggests that empirical bias-correction may enhance the utility of MAESTRO aerosol extinction data, which can make it a useful complement to existing satellite records, especially when multi-wavelength solar occultation data from other instruments are unavailable.