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

Overview & Synopsis

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 cm -1 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. Plain Language SummaryThe large ozone depletion occurring each year over the South Pole during the austral spring is strongly related to the presence of polar stratospheric clouds (PSCs). These clouds form at high altitudes under extremely cold conditions. In this work, we use satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) to detect one common PSC composition class, NATcontaining mixtures. It is the first time that such detections are reported by an instrument of this kind, which offers a much denser spatial and temporal sampling than others, but does not provide vertical information on the presence of NAT particles. We obtain systematic observations during the polar winter, allowing us to study their spatial and temporal distributions. By analyzing their occurrence in relation to other atmospheric parameters (temperatures and nitric acid abundances), we show a high degree of consistency with processes governing the chemistry of the polar stratosphere during winter.