[A-AS07] Atmospheric Chemistry

[AAS07-08] Relationship between appearance of polar stratospheric clouds and ozone destruction over Northern polar region in 2011 and 2020 based on CALIPSO observations

*Hideaki Nakajima^1,2, Miu Ogawa³, Kazuyuki Kita³, Michael C. Pitts⁴ (1.Earth System Division, National Institute for Environmental Studies, 2.Graduate School of Environmental Studies, Tohoku University, 3.Faculty of Science, Ibaraki University, 4.NASA Langley Research Center)

Keywords:ozone depletion, polar stratospheric clouds, PSC, Arctic, polar vortex, CALIPSO

Although stratospheric ozone loss occurs every year in Antarctica, Arctic ozone loss occurs only when stratospheric temperature gets low. Recently, substantial ozone loss occurred in Arctic in 1997, 2011, and 2020. Especially, the magnitude of Arctic ozone losses in 2011 and 2020 was comparable to that of in Antarctica. Satellite CALIPSO was launched in 2006, and is still in operation and measuring global cloud properties using two-wavelength lidars. It measures distribution and characteristics of polar stratospheric clouds (PSC) over both polar regions. In this study, we analyzed characteristics of Arctic PSCs in 2011 and 2020, and their effects on polar ozone loss. Figure 1 shows distribution and types of Arctic PSCs along a CALIPSO satellite track on 4 January 2011 over downstream of Greenland. The appearance of wave-ice-type PSC due to mountain-induce lee wave can be seen.

In this analysis, distribution and types of Arctic PSC was analyzed for the altitudes of 20, 17.5, and 15 km for each CALIPSO orbit (15 orbits per day in maximum) from January to March in 2011 and 2020. Local temperature and HNO₃ amount by Aura/MLS were also analyzed to see the PSC formation condition and the magnitude of denitrification. As a result, there were no major differences between the appearance of PSCs in January and February. However, stratospheric temperature was low in 2020 compared with 2011 in March, and appearance of PSC was greater in 2020. Ozone depletion started to occur in March when sunlight was available over the Arctic, and record-high ozone depletion was observed in 2020. The reason of this low temperature in 2020 could be attributed to the unusually strong polar vortex over the Arctic in this year.