Mapping NAT‐Containing Polar Stratospheric Clouds in the Antarctic Stratosphere Using Nadir Infrared Radiance Observations

Abstract Polar stratospheric clouds (PSCs) play a key role in the formation of the Antarctic ozone hole. Here, we report the first observations of the most abundant PSC composition class, NAT‐containing mixtures (one of whose components is nitric acid trihydrate, NAT, particles), from measurements of a passive nadir‐viewing sounder, the Infrared Atmospheric Sounding Interferometer (IASI). We show the unambiguous presence of the characteristic peak signature of small NAT particles near 820 in IASI spectra. By developing a detection method specific to the South Pole, we further demonstrate that NAT‐containing PSCs can be detected systematically during the polar winter, despite a reduced sensitivity over the continent. This method allows us to obtain an innovative data set in terms of spatial and temporal sampling. With respect to the physicochemical processes at play in the Antarctic stratosphere, we show a high degree of consistency between the 2008–2024 time series of detected NAT‐containing PSCs, stratospheric temperatures and total columns of nitric acid.