Relative Impact of GHG Forcing and Ozone Depletion/Recovery in Southern Hemisphere Atmospheric Circulation and Regional Precipitation Changes.

MINDLIN, JULIA; TEODORE SHEPHERD; CAROLINA VERA; MARISOL OSMAN

Conferencia; AGU Fall Meeting; 2020

American Geophysical Union

The summer atmospheric circulation of the Southern Hemisphere (SH) has exhibited a marked trend over the last decades of the twentieth century, characterized by a spatial pattern that resembles the positive phase of the Southern Annular Mode (SAM), and is interpreted as a poleward shift in the mid-latitude eddy-driven jet stream. This late 20th century trend has been mainly attributed to a delay in stratospheric polar vortex breakdown associated with ozone depletion, and ozone recovery can be expected to act in the opposite direction. On the other hand, GHG increases are projected to lead to a delay in stratospheric vortex breakdown which could sustain the poleward shift of the jet stream, as well as to influence the mid-latitude jet stream through other remote drivers, e.g. through tropical warming or the expansion of the Hadley cell. These different drivers have recently been shown to influence regional precipitation changes in a complex way. With this work we evaluate the combined impact of ozone depletion/recovery and GHG increase on projected jet stream and regional precipitation changes in the SH, distinguishing between stratospheric and tropospheric pathways. This is achieved by developing storylines of both the ozone depletion and the ozone recovery periods, using both CMIP5 and CMIP6 models.