The Dynamics of Stratospheric Warmings and Their Connection to Northern Annular Mode Variability

Northwest Research Associates, Incorporated, Seattle WA

Investigators

Abstract

The project will investigate the dynamical influence of the stratosphere on tropospheric variability in the middle and high latitudes of the Northern hemisphere. Interest in stratospheric circulation, including sudden warming, has recently been rekindled by observational analyses which suggest that a primary mode of tropospheric variability in polar latitudes--the annular mode--is influenced by the downward migration of annular anomalies from the stratosphere. Variations in stratospheric polar vortex have been linked to seasonal anomalies in the tropospheric zonal-mean zonal winds and circulation patterns such as the Arctic Oscillation/North Atlantic Oscillation. These patterns have profound impact on European and North American climate and weather. Drs. Ortland and Dunkerton will conduct a dynamically oriented analysis of the mechanisms coupling the troposphere and stratosphere, and the subtropics and midlatitudes. The PIs will use a quasi-linear primitive equation model to study the interaction of zonal-mean zonal flow (annular component) and the planetary-scale Rossby waves. The project will advance the understanding and modeling of dynamical interactions of the troposphere and stratosphere, and shed light on the evolution of the annular mode. This research will also be helpful in understanding the mechanisms producing the observed climate trends.