Abstract
In this study, we analyse the dynamical evolution, and identify the major warming (MW) and minor warming events of the past 11 Arctic winters (2010/11–2020/21). During the period, MW is found in 4 winters and is in January for 2012/13, 2018/19 and 2020/21 and in February for 2017/18. A major final warming is observed in the year 2015/16. The most severe MW occurred in the 2012/13 winter, for which a rise in temperature of about 30 K is found at 60° N. The investigation of tropospheric wave forcings for the period reveals that the MW in 2012/13 and 2017/18 is forced by the combined activity of waves 1 and 2, whereas the MW in 2018/19 and 2020/21 is driven by wave 1. Studies have shown that the frequency of Sudden Stratospheric Warming (SSW) in the Arctic has been increasing since 1957/58, which is about 1.1 MWs/winter during 1998/99–2009/10. However, this frequency decreases to 0.36 MWs/winter in the period 2010/11–2020/21 and 0.74 MWs/winter in 1998/99–2020/21. An inverse relationship is observed between the period of occurrence of SSWs and total column ozone (TCO) in the Arctic for the past 11 winters (2010/11–2020/21). For instance, the temperature in the lower stratosphere in January, in which most warmings occur, shows a statistically significant high positive correlation (0.79) with the average TCO in January–March. Therefore, this study assists in understanding the relationship between inter-annual variability of ozone and the occurrence of SSWs.
Highlights
The presence of Sudden Stratospheric Warming (SSW) events drives the dynamic nature of Arctic stratosphere in most winters
The observed temperature increase is in the range of 30–40 K at 60°–90° N/S latitude, and it is followed by a reversal of westerlies during major warming (MW), but only a weakening of the westerlies during minor warming [5, 6]
The occurrence of major warming was identified in 4 winters; namely 2012/13, 2017/18, 2018/19 and 2020/21
Summary
The presence of Sudden Stratospheric Warming (SSW) events drives the dynamic nature of Arctic stratosphere in most winters. The meridional temperature gradient is reversed, and the direction and speed of the zonal winds are changed during the major SSW period [3, 4]. The classification of MW events to the split and displacement types differ based on the criterion such as the central dates and datasets used. The occurrence of SSW has been increasing since its earliest documentation in January 1952 This rate of increase in frequency differs in different studies based on the criterion chosen for the classification of warming. We use the Modern-Era Retrospective Analysis for Research and Applications (MERRA-2) data to investigate the changes in temperature and zonal winds [43] These reanalysis datasets have a resolution of 0.5° × 0.625° and a temporal resolution of three hours at 42 pressure levels. The relationship between the concentration of ozone and the presence of MW in the winters is evaluated using the total column ozone (TCO) obtained from the TOMS
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