Effects of Sudden Stratospheric Warming Events on the Distribution of Total Column Ozone over Polar and Middle Latitude Regions

Vazhathottathil Madhu

doi:10.4236/ojms.2016.62025

Abstract

In winter the polar stratosphere is extremely cold. During the Sudden Stratospheric Warming events, the polar stratospheric temperature rises concurrently zonal-mean zonal flow weakens over a short period of time. As the zonal flow weakens, the stratospheric circulation becomes highly asymmetrical and the stratospheric polar vortex is displaced off the pole. The polar stratospheric temperature rises by 50°C and the stratospheric circumpolar flow reverses direction in a span of just few days. Sudden Stratospheric Warming (SSW) leads to significant changes in the rate of several chemical reactions which occur in the polar stratosphere. During such events, the dynamical fields in the polar stratosphere completely altered and columnar ozone changed. This study concentrated on the variability of winter polar vortex, meridional temperature gradient and associated changes in the Total Column Ozone (TCO) over the polar and middle latitude regions. It is found that changes in the amount of column ozone are positively correlated with polar lower stratospheric temperature with colder (warmer) temperature correlating with less (high) amount column ozone. But in the middle latitude region we observed negative correlations between ozone concentration and stratospheric temperature. In almost all cases there is sudden increase of ozone concentration over the pole and after few days the value is reduced when the warming effect is weak. During SSW events there observed an increase of 30 DU in TCO from the average value over the pole and if the SSW is strong TCO is found to rise by 50 DU. But in the middle latitude approximately 10 DU increase is noted. From the above results it may be concluded that variability of column ozone depends on dynamic and stratospheric chemistry over the poles and in middle latitude the variability can be attributed to the dynamical aspects. Anomaly of column ozone is higher during sudden stratospheric warming events over both polar and middle latitude region. The meridional temperature gradient reverses first and after two days polar vortex changes its direction or weakens followed by an increase of column ozone over the polar region. An increase of 30° Kelvin in the average temperature value noted over the polar region during sudden stratospheric warming events.

Highlights

Ozone plays a major role in the chemical and thermal balance of the atmosphere
Extreme winter stratosphere leads to an increasing volume of air cold enough for the occurrence of polar stratospheric clouds (PSCs), which in turn leads to more ozone loss inside the polar vortex [42]
Reactions occur on the surface of PSC particles that convert the reservoir forms of chlorine gases, ClONO2 and HCL, to reactive forms, such as ClO, which lead to catalytic ozone destruction when sunlight is available

Summary

Introduction

Ozone plays a major role in the chemical and thermal balance of the atmosphere. The British chemist Sydney Chapman proposed a cycle of chemical reactions driven by the sun as the mechanism for producing ozone layer in the stratosphere. Chapman showed that ozone (O3) was created when oxygen atoms and oxygen molecules combine. Atmospheric dynamics is known to be a major factor in the variability of stratospheric ozone distribution over the tropics from year to year. Transport and wind motion in the stratosphere are interconnected with those in the troposphere and play crucial roles in ozone distribution over the tropic. There is considerable evidence that the atmospheric total ozone amount is strongly influenced by the stratospheric circulation [5] [6]. Earlier works have consistently shown that good correlation exists between the total ozone amount and stratospheric geopotential heights, stratospheric temperature, and the tropopause height [7] [8]

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Conclusion