This work analyzed ERA5 (ECMWF ReAnalysis) data from 1979 to 2018 to study changes in stratospheric gravity waves (GWs) associated with stratospheric sudden warming (SSWs). GW variations are examined by separating them into polar vortex split and displacement events. In general, GW amplitudes show enhancements prior to the wind reversal at 10 hPa and 60°N and reductions after the wind reversal. GW enhancements are larger during polar vortex split events compared to displacement events, likely due to the location of the polar vortex and background wind conditions. Locations of GW enhancements are different between split events and displacement events and these locations correlate with the locations of polar vortex edge where background wind is strong. GW drag (GWD) and Eliassen-Palm (EP) flux divergences are also analyzed to understand GW contributions to occurrences of SSWs. Our results indicate maximum GWD prior to SSWs are ~18% of the total drag, and timing of eastward zonal wind weakening is coincident with enhancements of westward GWD. These results indicate that although the main driver of SSWs are planetary waves, GWs can contribute to the occurrences of SSWs.

这项工作分析了1979年至2018年的ERA5（ECMWF ReAnalysis）数据，以研究与平流层突然变暖（SSWs）相关的平流层重力波（GWs）的变化。通过将GW变化分为极地涡旋分裂和位移事件进行检查。通常，GW振幅显示在10 hPa和60°N的风向逆转之前增强，而在风向逆转后减小。相较于位移事件，在极地涡旋分裂事件期间，GW的增强更大，这可能是由于极地涡旋的位置和背景风的条件。在分裂事件和位移事件之间，GW增强的位置是不同的，这些位置与背景风较强的极地涡旋边缘的位置相关。还分析了GW阻力（GWD）和Eliassen-Palm（EP）通量散度，以了解GW对SSW发生的贡献。我们的结果表明，在西南偏南之前的最大GWD约为总阻力的18％，而向东纬向风减弱的时机与向西GWD的增强相吻合。这些结果表明，尽管SSW的主要驱动力是行星波，但GW可以促成SSW的发生。