Nonequilibrium Statistical Mechanics of Sudden Stratospheric Warming
Abstract
Climate models are often perturbed by stochastic forcing to capture uncertainty, unresolved processes, and possible regime shifts. Examples include sea ice instabilities, rapid intensification of hurricanes, and sudden stratospheric warming (SSW), all of which develop through complex pathways in high-dimensional phase space. The causes and effects of SSW are being actively investigated through simulation experiments. We study SSW using transition path theory, a mathematical framework of nonequilibrium statistical mechanics to calculate reaction rates and most-probable paths. We compute these dynamical quantities both for the stochastically forced quasi-geostrophic potential vorticity model from Birner & Williams (2008), and observational data from the NOAA SSW Compendium. Transition path theory allows us to forecast SSW probabilistically given the initial state of the atmosphere, using a "reaction coordinate" for monitoring progress toward a transition. We also reconstruct a probability distribution of reaction paths, which reveals coherent structures (e.g. eddies) that typically accompany SSW events. In this way, transition path theory offers a data-driven perspective on physical onset mechanisms of SSW, and a useful comparison with previous studies on its relationship to the Madden-Julian Oscillation, blocking events, and planetary waves.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMNG11A..05F
- Keywords:
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- 3336 Numerical approximations and analyses;
- ATMOSPHERIC PROCESSESDE: 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 4534 Hydrodynamic modeling;
- OCEANOGRAPHY: PHYSICALDE: 7504 Celestial mechanics;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY