Observations from Atmospheric Chemistry Experiment–Fourier Transform Spectrometer (ACE-FTS) are used to examine global stratospheric water vapour trends for 2004–2021. The satellite measurements are used to quantify trend contributions arising from changes in tropical tropopause temperatures, general circulation patterns, and methane concentrations. While most of the observed trends can be explained by these changes, there remains an unaccounted-for and increasing source of water vapour in the lower mid-stratosphere at mid-latitudes, which is discussed.

We present a 17-year stratospheric age-of-air dataset derived from ACE-FTS satellite measurements of sulfur hexafluoride. This is the longest continuous, global, and vertically resolved age of air time series available to date. In this paper, we show that this dataset agrees well with age-of-air datasets based on measurements from other instruments. We also present trends in the midlatitude lower stratosphere that indicate changes in the global circulation that are predicted by climate models.

The eruption of Hunga Tonga-Hunga Ha'apai injected large amounts of water vapor and sea salt into the stratosphere, altering traditional views of volcanic aerosols. Using balloon-borne samplers, we collected aerosol samples and found high levels of sea salt and calcium, suggesting sulfate depletion due to gypsum formation. These findings highlight the need to consider sea salt in climate models to better predict volcanic impacts on the atmosphere and climate.

Ozone measurements from the ACE-FTS satellite instrument have been compared to worldwide balloon-borne ozonesonde profiles using pairs of closely spaced profiles and monthly averaged profiles. ACE-FTS typically measures more ozone in the stratosphere by up to 10 %. The long-term stability of the ACE-FTS ozone data is good, exhibiting small (but non-significant) drifts of less than 3 % per decade in the stratosphere. Lower in the profiles, the calculated drifts are larger (up to 10 % per decade).

This paper investigates the vertical impacts of the anomalous 2023 Canadian wildfire season using multiple satellite instruments. Our results highlight that despite a record-breaking area burned, only a small amount of smoke managed to enter the stratosphere. This shows that the conditions for deep convection were rarely met in the 2023 wildfire season, suggesting that even a massive area burned is not necessarily an indicator of stratospheric perturbations.