A modeling study of teleconnections and their tropical sources

Abstract

The linkage between large scale weather patterns that are recurring and persisting is called ``teleconnection``. The teleconnections have a large impact in the nature, the humans and the society. Most of them can be understood by propagation of planetary waves, such as the Rossby or the Kelvin waves. The major atmospheric jet streams can act as waveguides for Rossby waves as they can trap the energy from a vorticity source and transfer the information around the globe, alternating the weather patterns and creating teleconnections. We wonder how different aspects of the jet, such as the jet strength, width and location can constrain specific features of the trapped, zonal waves such as their wavenumber and amplitudes. The systematic analysis is done with the use of reanalysis data and a barotropic model. The major source of atmospheric variability over the Northeast Atlantic, Europe and North America is the teleconnection North Atlantic Oscillation (NAO). We investigate the contribution of tropical and extratropical atmospheric forcing mechanisms to the formation of the NAO pattern, using a barotropic model and focusing on time scales of 10-60 days. The tropical Indian Ocean (IO) exhibits notable atmospheric variability influencing the climate not only on regional, but also on global scale. The Seychelles Dome (SD) in the Southwest IO is a region characterized by a shallow thermocline that experiences large variability and strong seasonal upwelling. The variance of the SD is suggested to have an impact on the IO weather and on teleconnections. We investigate the local and remote response of the coupled ocean-atmosphere system to a shallow SD event, running ensemble experiments with the coupled EC-Earth model.