An unusual autumn Elevated Stratopause Event (ESE)

The Earth’s northern winter polar vortex is a highly variable region. Sometimes, it becomes a beautiful demonstration of atmospheric coupling. Enhanced planetary waves, originated down in the troposphere, interact with the stratospheric mean flow and weaken or even break the vortex. The otherwise cold winter stratosphere suddenly warms up. The perturbation may propagate to lower altitudes, eventually affecting the surface weather in extra-polar regions. 
Every so often, a warm stratopause reappears at unusually high altitudes after a sudden stratospheric warming, hence the name Elevated Stratopause Event (ESE). A strong descent then occurs and dry NOx-rich air, involved in ozone destruction, is injected into lower altitudes. These events generally occur during Arctic winter, when the vortex perturbations are more dramatic. Indeed, until now, no ESE had ever been observed outside of winter. For the first time, we detected such an event during autumn.  The subsequent unusually strong descent was comparable to ESEs linked to mid-winter major sudden stratospheric warmings.
In this seminar, we will review together the sequence of mechanisms taking place before and during ESEs and will describe the November event in detail by using MIPAS measurements with support of MERRA2 re-analysis data.

18/10/2018 - 12:30
Dr. Maya García Comás