Storm Tracks and Extreme Weather: A Dynamical Perspective on Climate Change and Its ImpactsJeffrey Yin
A consistent poleward shift and intensification of the midlatitude storm tracks is found in an ensemble of 21st century climate simulations performed by 15 coupled climate models. The poleward shift of the storm tracks also tends to be accompanied by poleward shifts in surface wind stress and precipitation, and a shift towards the high index state of the annular modes. Experiments with a Held-Suarez idealized GCM indicate that the poleward shift and intensification of the storm tracks could plausibly be caused by the rise in tropopause height associated with increased greenhouse gases. An eddy energy budget analysis indicates that more eddy energy is produced due to the reduction of static stability near the tropopause. The resulting increase in transient momentum fluxes tends to pull the midlatitude jets, and storm tracks, poleward.
Preliminary results are presented on shifts of extreme precipitation events in a 7-member ensemble of 21st century climate simulations performed by CCSM3. Results are quite noisy, indicating the need for a larger ensemble, but a poleward shift in extreme precipitation events appears to correspond to the poleward shift of the storm tracks. It is argued that the effect of large-scale climate variability and change on extreme weather events can be more easily understood by first examining the effect of the large-scale changes on extreme dynamical events.
7 December 2005
2 PM/ DSRC 1D 403