Oindrila Nath
Oindrila Nath

Sudden Stratospheric Warmings – Teleconnection with the Tropics

Sudden stratospheric warming, commonly known as SSW, is a polar winter phenomenon occurring in the Northern Hemisphere (except the two events of 2002 and 2019 occurred in the southern). This is mainly triggered by the propagation of large-scale planetary waves from the troposphere to the stratosphere. The interaction of the propagating waves with the background winds (polar westerlies) results in the deceleration and finally dissipation of the wave – the momentum gets deposited and converted into heat, resulting in increase in the background temperature. As per the WMO standards, SSW is identified by an abrupt rise in stratospheric temperature at 10 hPa. SSW is accompanied by the distortion or splitting of the polar vortex, which varies from one warming event to another.


Though SSW is a high latitude dramatic event, its signature has been found in the tropical and lower latitudes. However, due to lack of long-term spatial and temporal data coverage by satellite observations, tropics was not of much interest to study the impact of SSW. Since last few decades, researchers have started looking into the lower latitudes and SSW linkage. The dynamical coupling over the tropics is much more complex and inclusive of the periodic oscillations viz. ENSO, QBO, BDC. The teleconnections of the high-latitude SSW event and low-latitude dynamics and chemistry is something worthwhile to look at. And there are not much plausible explanations about the linking mechanism between the pole and the tropics during SSW.


• Establishing the teleconnections between polar SSW event and tropics will be important for the climate studies, especially for the mitigation strategies.
• SSW is responsible for the recent cold outbreaks in the mid to high latitude countries like in the Northern part of America and Eurasia, and it has been modulating the weather in a much drastic way than expected. If this polar phenomenon is found to have some profound effect on the tropical dynamics and/or chemistry in the changing climate, it will be an important aspect to look into, in case any global prediction has to be made about climate change.


1. Nath, O., Sridharan, S., 2014. Long-term variabilities and tendencies in zonal mean TIMED– SABER ozone and temperature in the middle atmosphere at 10 –15°N. Journal of Atmospheric and Solar-Terrestrial Physics. 120 (2014).1-8. DOI:10.1016/j.jastp.2014.08.010.
2. Nath, O., Sridharan, S., Gadhavi, H., 2015. Equatorial stratospheric thermal structure and ozone
variations during the sudden stratospheric warming of 2013. Journal of Atmospheric and SolarTerrestrial Physics. 122 (2015). 129-137. DOI: 10.1016/j.jastp.2014.11.003.
3. Nath, O., Sridharan, S., 2015. Chemical composition during SSW Equatorial middle atmospheric
chemical composition changes during sudden stratospheric warming events Chemical composition
during SSW. Atmospheric Chemistry and Physics 15(15):23969-23988. DOI: 10.5194/acpd-15-23969-
4. Nath, O., Sridharan, S., Naidu, C., V., 2017. Seasonal, interannual and long-term variabilities and
tendencies of water vapour in the upper stratosphere and mesospheric region over tropics (30°N30°S). Journal of Atmospheric and Solar-Terrestrial Physics. Volume 167, January 2018, Pages 23-29.
DOI: 10.1016/j.jastp.2017.07.009.
5. Nath, O., Sridharan, S., 2019. Seasonal, interannual and SSW related variations of middle atmospheric
N2O and NOx over low latitudes. Journal of Atmospheric and Solar-Terrestrial Physics. Volume 198, February 2020, 105043. DOI: 10.1016/j.jastp.2019.05.007.
6. Oindrila Nath, Bhupendra Bahadur Singh, Ravi Kumar Kunchala, 2021. ENSO and IOD signatures inthe
tropical Upper Troposphere Lower Stratosphere (UTLS) Ozone, under review (International Journal of
Remote Sensing).