Atmosphere Ocean Science Colloquium

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Wave Effects in the Tropical Tropopause Layer

Speaker: Joan Alexander, NWRA

Location: Warren Weaver Hall 1302

Date: Wednesday, November 13, 2013, 3:30 p.m.

Synopsis:

The tropical tropopause layer (TTL) is an entry-point for air entering the stratosphere from the troposphere. The global transport circulation moves air upwards through the TTL and lower stratosphere, then poleward where it descends and eventually returns to the troposphere. Temperatures in the TTL reach extremely cold values, and air entering the stratosphere is effectively freeze-dried, leading to very dry conditions throughout the stratosphere. Despite small concentrations,decadal-scale changes in stratospheric water vapor have acted to significantly accelerate and slow the rates of global warming in recent decades, and the changes are believed tied to changes in the stratospheric transport circulation. However the mechanisms causing these changes remain illusive. Climate models predict a steady acceleration of the transport circulation as a response to greenhouse gas induced climate change, but such changes have not been observed to date. Our poor understanding of the processes controlling past variability in TTL temperatures and the stratospheric transport circulation results in a significant uncertainty in decadal-scale projection sof global warming. Using both observational analyses and theoretical and global dynamical models, we examine varied roles of tropical waves in driving temperature variability and variability in the transport circulation in the TTL.