Tropospheric-stratospheric wave propagation during El Nino-Southern Oscillation

摘要

Traditional and 3-D extended Eliassen-Palm (EP) fluxes for the globe between the 3 and 600 hPa levels are used to calculate El Nino-Southern Oscillation (ENSO) composites. Few of the warm minus cold departures of the traditional EP fluxes are significant at the 95% confidence level. In contrast, the ENSO composite differences of the longitudinally dependent extended EP flux have broad regions of significance for a wide range of latitudes, longitudes, and heights. During an ENSO event, there are significant vertical fluxes of wave energy across the tropopause over the subtropical Pacific. In addition, there is substantial meridional exchange of wave energy in the upper troposphere and lower stratosphere in this region. Proceeding northward, the changes in the stratosphere arc associated with meridional exchanges of wave energy and strong vertical fluxes of wave energy across the Pacific and North America. The higher-latitude changes have a westward tilt with height and eastward group velocities, both suggesting the importance of Rossby waves. In the Atlantic region, there are strong downward fluxes of wave energy, which may be part of an important ENSO pathway into Europe. Overall, these results strongly suggest the importance of nonzonally averaged dynamics in the stratospheric responses to ENSO.