Volcanic eruptions can contribute to polar ozone depletion when volcanic aerosol propagates into the tropical or polar stratosphere. During the period from 1850 to the present, none of the eruptions of extratropical volcanoes in the Northern Hemisphere was observed in the tropical stratosphere and, therefore, could not contribute to the polar vortex strengthening in the conditions of an increase of the stratospheric equator-to-pole temperature gradient as a result of an increase of the tropical stratospheric temperature. However, this is possible during mid-latitude volcanic eruptions with VEI ≥ 6 and during high-latitude volcanic eruptions with VEI ≥ 7. During the period from 1980 to the present, none of the eruptions of extratropical volcanoes in the Northern Hemisphere influenced the intensity of Arctic ozone depletion, since in some cases the ejection of eruption products was outside the polar vortex, and in other cases the height of the ejection was insufficient and the volcanic aerosol was removed from the stratosphere as a result of sedimentation even before the polar vortex formation. However, the effect of extratropical volcanic eruptions on Arctic ozone depletion is possible when the eruption products enter the polar vortex, or when a volcanic aerosol propagates into the polar region before the polar vortex formation with a sufficient lifetime in the stratosphere, determined, in particular, by the height of the ejection.
This work considers a series of numerical experiments to identify the direct role of the sea ice reduction process in forming climatic trends in the northern hemisphere. We used two more or less independent mechanisms of ice reduction. The first is traditionally associated with increasing the concentration of carbon dioxide in the atmosphere from the historic level of 360 ppm to the level corresponding to the maximum concentration in implementing the mildest scenario RCP 2.6 - 450 ppm. Due to this growth, the average air temperature in the Arctic increases, and, by this, the ice volume decreases. The second mechanism is associated with a decrease in the reflectivity of ice and snow. As a result, the amount of solar radiation absorbed by the ice increases while the ice volume decreases. We assume that comparing the results of these two experiments allows us to judge the direct role of ice reduction, regardless of the reasons that caused this reduction.
The stratospheric polar vortex strength in spring determines to a great extent the duration and intensity of ozone depletion in the polar regions. A temperature increase in the lower subtropical stratosphere in spring leads to an increase in the stratospheric equator-to-pole temperature gradient and the subsequent strengthening of the Antarctic polar vortex, accompanied by severe springtime ozone depletion. At the same time, the unusual weakening of the Antarctic polar vortex was observed in the spring of 2019. An abnormal temperature decrease in the lower subtropical stratosphere was recorded in the same time period and probably led to a decrease in the stratospheric equator-to-pole temperature gradient and the subsequent weakening of the polar vortex.
The stratospheric polar vortex strength in spring determines to a great extent the duration and intensity of ozone depletion in the polar regions. The size of the Antarctic ozone hole usually reaches its maximum in September and then drops off during October and November. However, in 2015, a significant increase in the ozone hole area relative to climatological mean values was observed in October under the strong polar vortex conditions, and in 2002 its abnormal decrease was recorded as a result of the splitting of the polar vortex in September. A significant increase and decrease in temperature of the lower subtropical stratosphere in the spring of 2015 and 2002, which contributed to a corresponding increase and decrease in the stratospheric meridional temperature gradient during these years, was considered as a possible cause for the polar vortex strengthening in 2015 and its weakening in 2002.
In a number of works, it is shown that the reaction of extratropical circulation to strong eruptions of tropical volcanoes is the strengthening of the Northern polar vortex. The observations show that at the winter following after the autumn eruptions of volcanoes in the tropical belt there is a positive anomaly in the intensity of the polar vortex. In this paper, the reaction of the Northern polar vortex to tropical volcanic eruptions is numerically investigated. The possible mechanism of vortex amplification is shown.
Presented is a recently started Russian Science Foundation project “Virtual computational information environment for analysis, evaluation and prediction of the impacts of global climate change on the environment and climate of a selected region” aimed at development of accessible in Internet a computation and information environment providing unskilled in numerical modeling and software design specialists, decision-makers and stakeholders with reliable and easily used tools for in-depth statistical analysis of climatic characteristics, and instruments for detailed analysis, assessment and prediction of impacts of global climate change on the environment and climate of the targeted region. Two actively discussed nowadays problems are addressed by the project. The first one is a development of an environment in which scientists from different disciplines, stakeholders and decision makers, regardless of their geographical position, can freely access various data resources and processing services through a Web browser. Since progress in development of so called virtual research environment is based on information-computational technologies it will be discussed in this paper in more details. The second problem belongs to basic and applied climatology and will be discussed here rather briefly. It is a provision of interested parties with detailed climatic and ecological characteristics of targeted region and tools allowing get scientifically solid data necessary for the study of regional economic, political and social consequences of global climate change.
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