Non-uniform dissipation of the Antarctic ozone hole

The evolution o f the Antarct ic ozone hole is illustrated fo r 1985·1989 and 1990 springs.A detailed study for 1986.19 89 and 1990 events indicates that the evolution. which occurs in ea rly October . isfairly unifo rm over the South Pole. Hence the fluctuations observed at Syowa, McMurdo and Palmer duringthis period arc mostly due to the vortex \''3.11 passing in and out over these periferial loca t ions. However, later inNovember when the hole is dissipating, the vortex may shift from the South Pole in any direction and may alsocome back or intensify on Sou th Pole before finally disappearing. At South Pole. the recovery started by Octoberend in 19S5. 19R6 and 1988 but later in 19R7 (November end), 1989 {November beginning) and 1990 (Novemberend •.

Rapid increase in dichloromethane emissions from China inferred through atmospheric observations

With the successful implementation of the Montreal Protocol on Substances that Deplete the Ozone Layer, the atmospheric abundance of ozone-depleting substances continues to decrease slowly and the Antarctic ozone hole is showing signs of recovery. However, growing emissions of unregulated short-lived anthropogenic chlorocarbons are offsetting some of these gains. Here, we report an increase in emissions from China of the industrially produced chlorocarbon, dichloromethane (CH2Cl2). The emissions grew from 231 (213–245) Gg yr−1 in 2011 to 628 (599–658) Gg yr−1 in 2019, with an average annual increase of 13 (12–15) %, primarily from eastern China. The overall increase in CH2Cl2 emissions from China has the same magnitude as the global emission rise of 354 (281−427) Gg yr−1 over the same period. If global CH2Cl2 emissions remain at 2019 levels, they could lead to a delay in Antarctic ozone recovery of around 5 years compared to a scenario with no CH2Cl2 emissions.

Characterization of aerosol number size distributions and their effect on cloud properties at Syowa Station, Antarctica

We took aerosol measurements at Syowa Station, Antarctica, to characterize the aerosol number–size distribution and other aerosol physicochemical properties in 2004–2006. Four modal structures (i.e., mono-, bi-, tri-, and quad-modal) were identified in aerosol size distributions during measurements. Particularly, tri-modal and quad-modal structures were associated closely with new particle formation (NPF). To elucidate where NPF proceeds in the Antarctic, we compared the aerosol size distributions and modal structures to air mass origins computed using backward trajectory analysis. Results of this comparison imply that aerosol size distributions involved with fresh NPF (quad-modal distributions) were observed in coastal and continental free troposphere (FT; 12 % of days) areas and marine and coastal boundary layers (1 %) during September–October and March and in coastal and continental FT (3 %) areas and marine and coastal boundary layers (8 %) during December–February. Photochemical gaseous products, coupled with ultraviolet (UV) radiation, play an important role in NPF, even in the Antarctic troposphere. With the existence of the ozone hole in the Antarctic stratosphere, more UV radiation can enhance atmospheric chemistry, even near the surface in the Antarctic. However, linkage among tropospheric aerosols in the Antarctic, ozone hole, and UV enhancement is unknown. Results demonstrated that NPF started in the Antarctic FT already at the end of August–early September by UV enhancement resulting from the ozone hole. Then, aerosol particles supplied from NPF during periods when the ozone hole appeared to grow gradually by vapor condensation, suggesting modification of aerosol properties such as number concentrations and size distributions in the Antarctic troposphere during summer. Here, we assess the hypothesis that UV enhancement in the upper troposphere by the Antarctic ozone hole modifies the aerosol population, aerosol size distribution, cloud condensation nuclei capabilities, and cloud properties in Antarctic regions during summer.

QUASI-BIENNIAL OSCILLATION OF ZONAL WIND IN THE EQUATORIAL STRATOSPHERE AND ITS INFLUENCE ON INTERANNUAL FLUCTUATIONS IN THE DEPTH OF THE ANTARCTIC OZONE HOLE

The Antarctic ozone hole is observed annually in spring due to the complex influence of photochemical and dynamical processes. The increased concentration of ozone-depleting substances in the atmosphere causes a long-term negative trend in total ozone (TO). Intense interannual fluctuations in TO against a background of the long-term trend associated with dynamic atmospheric processes do not allow assessing definitely the direction of the trend (growth/decline) in the recent years. Studying the dependence of interannual fluctuations in the ozone hole intensity on the equatorial quasi-biennial oscillation (QBO) allows identifying natural causes of variations and assessing the trend due to anthropogenic factors. The long-term QBO forecast allows predicting different phenomena that depend on the QBO.

Analysis of the Antarctic Ozone Hole in November

The factors responsible for the size of Antarctic ozone hole in November are analyzed. Comparing two samples of anomalously large and small November ozone hole with respect to 1980–2017 climatology in November, the results show that the anomalously large ozone hole in austral late winter is not a precondition for the anomalously large ozone hole in November. The size of Antarctic ozone hole in November is mainly influenced by dynamical processes from the end of October to mid-November. During large November ozone hole events, weaker dynamical ozone transport appears from the end of October to mid-November, which is closely related to planetary wave divergence in the stratosphere between 60°S and 90°S. Further analyses indicate that the wave divergence is partially attributed to less upward propagation of planetary waves from the troposphere, which is associated with weak baroclinic disturbances at the end of October. Subsequently, zonal wind speed in the upper stratosphere intensifies, and the distance between critical layer (U=0) and wave reflecting surfaces becomes larger. As a result, more planetary waves are reflected and then wave divergence enhances. The processes responsible for the anomalously small Antarctic ozone holes in November are almost opposite to those for the anomalously large Antarctic ozone holes.

Characterization of aerosol number size distributions and their effect on cloud properties at Syowa Station, Antarctica

We took aerosol measurements at Syowa Station, Antarctica to characterize the aerosol number–size distribution and other aerosol physicochemical properties. Four modal structures (i.e., mono-, bi-, tri-, and quad-modal) were identified in aerosol size distributions during measurements. Particularly, quad-modal structures were associated closely with new particle formation (NPF). To elucidate where NPF proceeds in the Antarctic, we compared the aerosol size distributions and modal structure to air mass origins computed using backward trajectory analysis. Results of this comparison imply that NPF occurred in free troposphere during spring and autumn, and in the free troposphere and boundary layer during summer. Photochemical gaseous products, coupled with UV radiation, play an important role in NPF, even in the Antarctic troposphere. With the appearance of the ozone hole in the Antarctic stratosphere, more UV radiation can enhance atmospheric chemistry, even near the surface in the Antarctic. However, linkage among tropospheric aerosols in the Antarctic, ozone hole, and UV enhancement is unknown. Results demonstrated that NPF started in the Antarctic free troposphere already in the end-August – early September by UV enhancement resulting from the ozone hole. Then, aerosol particles supplied from NPF during spring grow gradually by vapor condensation, suggesting modification of aerosol properties such as number concentrations and size distributions in the Antarctic troposphere during summer. Here, we assess the hypothesis that UV enhancement in the upper troposphere by the Antarctic ozone hole modifies the aerosol population, aerosol size distribution, cloud condensation nuclei capabilities, and cloud properties in Antarctic regions during summer.