Storm tracks are an important component of the general circulation and have significant impacts on weather and climate, both at regional and global scales. This project uses an hierarchy of models to study the dynamical impacts of water vapor on storm tracks. Most studies of storm track dynamics have made use of either dry dynamical models which ignored the impact of water vapor, or comprehensive general circulation models (GCM) that include all relevant physics but are expensive to run. In this project, a GCM that incorporates some of the interactions between water vapor and dynamics will be used. The advantage of using simplified physics compared to comprehensive GCMs, is that it will enable extensive experimentation of parameter space. Storms have crucial impacts on society and improved understanding of such phenomenon has significant broader impacts.
The primary goals pursued under this award were to elucidate what controls fundamental aspects of storm tracks (e.g., over the Atlantic and Pacific) and how they might change with climate. For example, we wanted to elucidate how the latitudinal position of storm tracks can change as the climate changes, and what controls the longitudinal extent of storm tracks. Among the significant outcomes of this research were the following: We showed that static stability changes near the equator can lead to poleward shifts of the remote midlatitude storm tracks, through a chain of mechanisms linking tropical to extratropical dynamics. We demonstrated that the longitudinal extent of storm tracks is self-limited, and not necessarily limited by friction over continents, as had been surmised. Storm tracks self-destruct downstream. Stationary waves generated by the same land-sea temperature contrasts that generate the storm tracks are important for limiting the longitudinal extent of storm tracks. We demonstrated that atmospheric stationary waves generated by warm ocean boundary currents (Gulf Stream, Kuroshio) transport cool air equatorward west of the ocean currents and of the storm tracks the currents generate. This in part accounts for the wintertime cold of eastern continental boundaries (e.g., U.S. East Coast) relative to western continental regions at similar latitudes (e.g., in Europe or over central Asia).
