Impact of Physical & Chemical Parameters on Polar Ozone Concentration

Abstract

An analysis of stratospheric composition in past has revealed tight correlations in between multiple tracer gases. This correlation is a result of the same transport mechanism to which tropospheric gases are subjected to while being transported to the stratosphere through meridional circulation. This study attempts to find out the correlation of one such tracer i.e. ozone with other gases, known to have a certain degree of influence over ozone concentration in the stratospheric layer of atmosphere. This study also takes advantage of correlations obtained to predict future values of ozone volume mixing ratio in the stratosphere. This study has been carried out by using advanced machine learning tools which have been proven in past to give very accurate quantitative results. Such a study gives an insight into how chemical parameters work in synchrony under the background of climatological fields and influence the indispensable stratospheric ozone layer. This study also intends to show the influence of climatological fields of several variables that are derived during periods of ozone index amplification and during its weakening on ozone concentration. The premise here is that there are several robust supporting meteorological fields in the troposphere and in the stratosphere that go hand in hand with the accepted role of the chlorofluorocarbons that are attributed to the growth of the ozone hole and the implication is that however, these chlorofluorocarbons are necessary but not sufficient for the production of the ozone hole, that is supported by favorable meteorological fields. During periods of unfavorable meteorology, the breakdown of the ozone does not occur. For the purpose of carrying out this study, we use the reanalysis dataset NCEP/NCAR analysis I for a duration of 41 years obtained from the archive of Physical Science division, Earth System Research Laboratory, NOAA. Polar meridional cell was one of the prominent variable examined in the process. The time tendencies of the ozone volume mixing ratio and of the intensity of the polar cell were calculated and used to identify those months during which there was a simultaneous rise or simultaneous decline in the time rate of change for both ozone gas volume mixing ratio and polar cell intensity. To further the study four cases were taken into consideration. Firstly, those months were considered during which both ozone and polar cell values were falling, thereafter those in which ozone was falling but polar cell value was rising and vice-versa, and lastly those months in which both were falling, as a function of time in all the cases. Sorting the climatology for these four separate possibilities, respective climatologies were constructed. For the given four cases, aforementioned, climatologies of variables apart from ozone volume mixing ratio and polar cell were also considered. These comprised of the polar jet stream and the subtropical jet stream, the 50 hPa level air temperatures and the convergence of flux of temperature at that level. Finally, the results of this study exhibited robust differences in the atmospheric fields during the formation and weakening phases of the ozone hole, which was subjected to further analysis to find their influence, if any, over polar ozone layer.