Structure of Stratospheric Wave Responses to ENSO Convection

Generalized maximum covariance analysis (GMCA) has been developed and applied to diagnosing the relationships between ENSO tropospheric heating variations and tropical stratospheric waves. GMCA identifies the most important patterns of covariability between interannual tropospheric heating variations and eddy zonal and meridional velocities, temperatures, and ozone mixing ratios in the tropics between 200 and 10 hPa. The first two sets of GMCA time coefficients have variations that are strongly related to ENSO and are highly correlated at a lag of about a year. The diagnosed spatial patterns have broad wavenumber 1 characteristics, which are associated with ENSO. These dominant modes of heating variations are linked to a rich three-dimensional pattern of stratospheric eddy perturbations over a wide range of lags. Generally, all major features propagate slowly to the east along with the tropospheric heating anomaly. In addition there is strong vertical coherence such that the strongest anomalies tilt westward from the bottom to the top of the domain. This tilt is associated with propagating wavenumber-1 gravity waves. The patterns are such that, in the lower stratosphere, regions of divergence, corresponding to upward motion, are associated with lower temperatures and reduced ozone mixing ratios and vice versa. These findings are consistent with adiabatic cooling of rising low–ozone concentration tropospheric air. Evidence suggests that the analyzed eddy variations of temperatures and winds are contributing to systematic changes in the zonal mean circulation.