Polar stratospheric nitric acid depletion surveyed from a decadal dataset of IASI total columns

• Published in: Atmospheric Chemistry and Physics
• Main Authors: C. Wespes, G. Ronsmans, L. Clarisse, S. Solomon, D. Hurtmans, C. Clerbaux, P.-F. Coheur
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2022
• Subjects: Physics; QC1-999; Chemistry; QD1-999; Antarctic; The Antarctic; Antarc*; polar night
• Online Access: https://doi.org/10.5194/acp-22-10993-2022; https://doaj.org/article/2db5b4e5307648dea9932dbb02e840c4

In this paper, we exploit the first 10-year data record (2008–2017) of nitric acid ( HNO 3 ) total columns measured by the IASI-A/MetOp infrared sounder, characterized by an exceptional daily sampling and a good vertical sensitivity in the lower-to-mid stratosphere (around 50 hPa ), to monitor the relationship between the temperature decrease and the observed HNO 3 loss that occurs each year in the Antarctic stratosphere during the polar night. Since the HNO 3 depletion results from the formation of polar stratospheric clouds (PSCs), which trigger the development of the ozone ( O 3 ) hole, its continuous monitoring is of high importance. We verify here, from the 10-year time evolution of HNO 3 together with temperature (taken from reanalysis at 50 hPa ), the recurrence of specific regimes in the annual cycle of IASI HNO 3 and identify (for each year) the day and the 50 hPa temperature (“drop temperature”) corresponding to the onset of strong HNO 3 depletion in the Antarctic winter. Although the measured HNO 3 total column does not allow for the uptake of HNO 3 by different types of PSC particles along the vertical profile to be differentiated, an average drop temperature of 194.2 ± 3.8 K , close to the nitric acid trihydrate (NAT) existence threshold ( ∼ 195 K at 50 hPa ), is found in the region of potential vorticity lower than − 10 × 10 −5 <math xmlns="http://www.w3.org/1998/Math/MathML" id="M21" display="inline" overflow="scroll" dspmath="mathml"><mrow class="unit"><mi mathvariant="normal">K</mi><mspace width="0.125em" linebreak="nobreak"/><msup><mi mathvariant="normal">m</mi><mn mathvariant="normal">2</mn></msup><mspace linebreak="nobreak" width="0.125em"/><msup><mi mathvariant="normal">kg</mi><mrow><mo>-</mo><mn mathvariant="normal">1</mn></mrow></msup><mspace width="0.125em" linebreak="nobreak"/><msup><mi ...