Variations Of Atmospheric Waves And Sea Surface Temperature During Statospheric Sudden Warming Events

Stratospheric sudden warming (SSW) is one of the most dramatic phenomena in the polar winter, whose effects could extend globally. Atmospheric temperature structure and wind field will be affected profoundly during SSW events. As SSW could induce couplings of different atmospheric layers globally, the study of its effects is of great significance to understand the atmospheric dynamical processes.There are three main parts of our study:1) based on the COSMIC temperature data and NCEP/NCAR reanalysis data, we investigated the variation of gravity wave (GW) activity in the polar region during the vortex-displacement SSW event in 2008 and the vortex-split SSW event in 2009; 2) we studied the changes of tropical background and Kelvin wave during SSW events using ERA-Interim reanalysis data and the results are validated by COSMIC data; 3) we applied statistical analysis to study the variation of sea surface temperature anomalies (SSTA) obtained from ERA-Interim reanalysis data.The results showed that:1?The zonal mean gravity wave activity in the polar region enhanced during two types of SSW events. The enhancement of gravity wave progressed downward along with the zonal wind reversal during the major warming events. During the downward progression, the magnitude of the GW enhancement kept relatively stable in the vortex-displacement event, while a clear reduction appeared in the vortex-split event. The GW activities display great spatial variability due to the location and strength of the polar vortex. In general, background wind was larger at the polar vortex edge, and smaller inside and outside of the polar vortex, so were the GW amplitudes. However, the enhancements of the GW activities didn't always correspond to the regions with the strongest wind. The association could be due to the selective transmission caused by the polar vortex wind and different sources of the GW.2?During SSW events, enhanced extratropical planetary wave forcing enhanced the meridional circulation, which caused upwelling in the tropical stratosphere. The upwelling further caused tropical cooling. Meanwhile, eastward zonal wind anomalies appeared in the tropical stratosphere. During SSW events, Kelvin wave activities showed clear coupling with the localized convection in the Indian Ocean and western Pacific (Indo-Pacific). The ratio of Kelvin contribution in driving the eastward zonal wind anomalies was much larger during SSW events than during non-SSW winters.3?The statistical results suggested the relationship between types of SSW events and ENSO phases. Nearly all the documented vortex-split SSW events occurred at the La Nina phase. The SSTA of the equatorial middle and eastern Pacific region became larger during the SSW events than that before the events, while the SSTA in the northern Pacific became smaller. The variations of SSTA in the equatorial middle and eastern Pacific were more significant at the El Nino and La Nina phases than that at the ENSO-neutral phase.