Environmental Science and Engineering Seminar

Variability of the polar stratospheric vortex impacts weather and climate patterns at the Earth's surface on timescales from weeks to decades. In this talk, I will discuss polar vortex variability on seasonal and decadal timescales, as well as the dynamics of tropospheric responses to forcing from the stratosphere (and, indeed, to external forcing in general, such as rising concentrations of greenhouse gases).

I will introduce an idealized, dynamically comprehensive atmospheric GCM that captures the observed hemispheric differences in stratospheric seasonal variability, and use this model setup to study the dynamics of tropospheric responses to stratospheric ozone depletion. I will discuss the implications of interactive chemistry in capturing these responses correctly, and demonstrate that it is not always accurate to describe the atmosphere's responses to external forcing by a single "annular mode". This will lead into a discussion of the application of Principal Oscillation Pattern analysis to extratropical winds, results from which suggest the existence of coupled, propagating annular modes, describing systematic latitudinal migrations of the mid-latitude jet.