Rossby wave propagation into the tropical stratosphere observed by the High Resolution Doppler Imager

Stratospheric wind observations by the High Resolution Doppler Imager on the Upper Atmosphere Research Satellite show that quasi-stationary Rossby waves propagate into the tropics. Rossby wave breaking and dissipation causes meridional transport and direct deposition of momentum, and has a significant influence on the evolution of the mean tropical winds in the upper stratosphere. Deeper penetration into the tropics occurs when the quasi-biennial oscillation is in its westerly phase above 30 km. During northern winter, subtropical momentum deposition by Rossby waves occurs only in late November through December, while during southern winter this occurs primarily in August and September.