Evaluation of ozone trends in the mesosphere/lower thermosphere using a new merged dataset of ozone profiles

Abstract. In recent years, the need for high-quality long-term mesospheric ozone records has become increasingly evident, as they are essential for understanding chemical, dynamical, and radiative processes in the middle and upper atmosphere and their coupling with the lower layers. Here, we present a new merged dataset of ozone profiles in the mesosphere and lower thermosphere (METEOR-O₃), created from several limb-viewing satellite instruments: HALOE, GOMOS, MIPAS, ACE-FTS, MLS, and SOFIE. The dataset covers the period from 1991 to 2023 and provides deseasonalized ozone anomalies in 10° latitude bins between 80° S and 80° N, from approximately 22 km to 100 km. The deseasonalized ozone anomalies are used for global and seasonal trend analysis. The results show positive upper stratospheric ozone trends in both hemispheres, with magnitudes of 1–2 % per decade between 35 and 45 km, indicating continued ozone recovery consistent with previous assessments. In contrast, mesospheric ozone (above ~60 km) exhibits negative trends of 1–3 % per decade, with the strongest decreases of about 8–10 % per decade near the mesopause. Seasonal analyses confirm positive trends in the upper stratosphere across all seasons and persistent negative trends in the upper mesosphere, strongest at high latitudes above 80 km. The METEOR-O₃ dataset provides the first global, long-term merged record suitable for detailed studies of mesospheric/lower thermospheric ozone variability and trend evaluation, providing valuable information for model validation and assessments of upper atmospheric changes.