ACE-FTS water vapour trends in the stratosphere-mesosphere

The Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) is a high spectral resolution (0.02 cm^-1) spectrometer on the SciSat satellite that has been taking solar occultation measurements of the Earth’s limb since February 2004. ACE-FTS measures vertical profiles of temperature/pressure and concentrations of over 60 trace gases, including ozone and water vapour, with a vertical resolution of ~2-6 km. From the beginning of the mission, ACE-FTS water vapour data exhibits a significant positive trend on the order of a few percent per decade throughout the stratosphere and mesosphere, in agreement with similar measurements from the Microwave Limb Sounder (MLS) and the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instruments. This study will investigate the link between ACE-FTS water vapour trends and decadal variations in other atmospheric parameters, including local and tropopause temperatures, ozone and methane concentrations, and solar flux, and will discuss how ACE-FTS measurements of HDO can be used to continue measuring background water vapour trends post-eruption of the Hunga Tonga-Hunga Ha’apai volcano, which injected ~160 Tg of water vapour (more than 10% of the stratospheric water vapour budget) into the stratosphere.