Dynamics of transient upwelling across the tropical tropopause

Tropical upwelling is a fundamental component of the stratospheric Brewer Dobson circulation (BDC), influencing temperatures, water vapor and chemical constituents throughout the global stratosphere. There is a substantial component of sub-seasonal variability in upwelling, with strong effects on temperatures and tracers in the tropical lower stratosphere. Upwelling diagnosed using momentum balance calculations from ERAinterim data demonstrate that transience is linked to the effects of extratropical wave forcing, with centers of action in the high latitude winter stratosphere and in the subtropical upper troposphere of both hemispheres. Zonal mean wind tendencies are an important part of communicating the remote wave forcing to the deep tropics. Dynamical patterns reflect clear differences in forcing the shallow vs. deep branches of the BDC; the shallow branch is most correlated with wave forcing in the subtropical upper troposphere, while the deep branch is mainly influenced by high latitude planetary waves.