[A-AS11] Atmospheric Chemistry

[AAS11-P13] Antarctic Haze Phenomena at Syowa Station, Antarctica: Seasonal and Vertical Distributions and Impact on Atmospheric Chemistry

*Keiichiro Hara¹, Kano Osato¹, Masanori Yabuki², Kazuo Osada³, Naohiko Hirasawa⁴, Masataka Shiobara⁴, Takashi Yamanouchi⁴ (1.Fukuoka University, 2.Kyoto University, 3.Nagoya University, 4.NIPR)

Keywords:Antarctic haze, Sea-salts, halogen, Ozone

Antarctic region is considered as “the cleanest” areas on the earth because of isolation from anthropogenic sources in mid- and low-latitudes and less source strength of anthropogenic species in the Antarctic areas. Nevertheless, haze conditions, i.e., low visibility resulting high aerosol concentrations, were observed at Syowa (Hara et al., JGR, 2010). Hara et al. (2010) showed that major aerosol species were sea-salt particles originated from sea-ice areas. To elucidate characteristics of the Antarctic haze phenomena (AHP) and their impact on atmospheric science, we analyzed aerosol data obtained at Syowa, as a part of atmospheric monitoring observations. Here, we used aerosol number concentrations measured by optical particle counters near surface (1997-2022) and aerosol vertical profiles observed by micro-pulse lidar (MPL, 2007-2020) and polarization MPL (PMPL, 2016-2022). Criteria to identify AHP and aerosol enhanced layers (AELs) over Syowa were in accordance with our previous works (Hara et al., JGR, 2010; ACP, 2014). During measurements in 1997 – 2022, 113 AHPs were identified at Syowa (2-8 events a year, mean 4.3 events a year). Both AHP and AELs appeared in April – October in spite of different criteria and showed maximum in August -September. The seasonal features might relate to variations of strong winds and sea-ice extent. AELs appeared in near surface – ca. 4 km over Syowa. Surface O₃ concentrations decreased often during AHP. Variations of the depleted O₃ amounts in AHP (dO₃) showed minimum in June (polar night) and maximum in August. Seasonal variations of dO₃ might be associated with photochemical processes and sea-salt and halogen chemistry. Considering appearance of AELs in boundary layer - free troposphere, AHP and AELs might have important contribution to (1) atmospheric oxidative potential by atmospheric sea-salt and halogen chemistry and (2) cloud processes and water cycles by suppling sea-salt aerosols as INPS and CCN.