The project will investigate dynamical mechanisms governing intraseasonal variability in the extratropical winter atmosphere. A leading example of this variability is the North Atlantic Oscillation - a meridional dipole in sea-level pressure (and related fields) in the extratropical Atlantic, which influences, notably, the European surface temperatures and precipitation in winter. The relationship of these regional modes with the annular (or hemispheric scale) modes of variability (e.g., Arctic Oscillation) is unclear, although its implications for extratropical variability and predictability are considerable. Dr. Robinson (U of Illinois) will investigate this relationship, including the role of tropical intraseasonal variability in influencing extratropical predictability, from numerical experiments with idealized dynamical models; these models can resolve the involved nonlinear interactions. These models provide an opportunity for systematic investigation of the fundamental dynamical issues, and Dr. Robinson will conduct a suite of experiments to fully investigate the involved mechanisms and interactions. The project will advance theoretical understanding and modeling of dynamical processes governing wintertime intraseasonal variability in the Northern extratropics, and potentially influence operational strategies for extended range weather forecasting.
