The stratospheric aerosol layer is mainly composed of sulfuric acid aerosol particles, which are microdroplets of a 75 % aqueous solution of sulfuric acid H2SO4. The most powerful source of stratospheric aerosol particles is large volcanic eruptions that inject significant amounts of sulfur dioxide SO2 into the stratosphere. Sulfur dioxide is oxidized to a sulfuric acid aerosol in the stratosphere within two weeks. The concentration of sulfuric acid aerosol in the lower stratosphere can increase by 1–2 orders of magnitude as a result of large volcanic eruptions. In this work, we presented a list of volcanic eruptions with the possible injection of aerosols into the stratosphere from 1800 to 2020.
The polar vortex strengthening leads not only to a temperature decrease in the lower stratosphere, but also to its increase in the upper stratosphere inside the vortex. Over the Antarctic, this dependence is observed from autumn to spring: in the upper stratosphere high temperatures are observed inside the polar vortex, and low temperatures occur outside, especially in spring. Over the Arctic, a temperature increase in the upper Arctic stratosphere is observed under conditions of the strengthening of the northern polar vortex. Temperature variations in the upper polar stratosphere are determined by the ozone concentration and depend on the dynamics of the polar vortex: with a decrease in the ozone content inside the strong vortex in the upper stratosphere, a temperature increase is observed.
The influence of the phase of the quasi-biennial oscillation (QBO) on the period of stratospheric ozone depletion over the Arctic is considered. The list of Arctic ozone depletion events from 1979 to 2019 is given. Most of the Arctic ozone depletion events have been well researched and extensively referenced. In this work, we examined ozone depletion observed in the winter of 1983, 1986 and 1987. Arctic ozone depletion occurring during the easterly and westerly phases of the QBO are usually observed in January and from February to April, respectively.
The influence of the stratospheric polar vortex on the tropospheric vortex begins to appear in November, is significantly enhanced from December to February and decreases in March. The strong stratospheric polar vortex centered over the North Pole enhances the tropospheric one, which largely repeats the shape and location of the stratospheric vortex during this period. The strong stratospheric polar vortex displaced relative to the pole can lead to the splitting of the tropospheric vortex. And finally, the splitting of the stratospheric vortex in winter leads to a significant weakening of the tropospheric one.
Black carbon (BC) aerosol particles, when being in sufficient amount in the Earth’s atmosphere, significantly influence its radiation balance and intensively deplete ozone by heterogeneous chemical reactions. There are many sources of BC in the troposphere: bio- and fossil-fuel burning, forest and bush fires, power generation and industrial processes, engines, etc. Aircraft emissions are widely assumed to be the principal source of BC nanoparticles in the stratosphere. In this paper, we make a hypothesis that Plinian eruptions with VEI ≥ 5 are a strong occasional source of long-lived BC in the stratosphere and suggest a possible mechanism of BC formation in volcanic conduits during the eruptions. Based on this hypothesis, and using the 1991 Pinatubo eruption (VEI = 6) as an example, we roughly estimate CBC and number concentration of BC particles NBC, which are required to cause ozone depletion events in the tropical stratosphere (at altitudes where ozone depletion cannot occur due to the presence of volcanic sulfuric acid aerosols). For this purpose, we use vertical ozone profiles obtained over the tropical station Hilo (19.72° N, 155.11° W; Hawaii) in September and November 1992. The September CBC and NBC values, we calculated for BC particles of mean radius 120 nm at an altitude of ~20.5 km, are 35.4 ±30.6 ng/m3 and (2.2±1.9)×106 particles/m3, respectively. The November CBC and NBC values for BC particles of mean radius 40 nm at an altitude of ~30 km are 25.3 ±7.8 ng/m3 and (4.2±1.3)×107 particles/m3, respectively.
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