NUMERICAL MODELING OF TRACER TRANSPORT WITHIN AND OUT OF THE LOWER TROPOSPHERIC ARCTIC REGION

The dispersion of passive tracer within and out of the Arctic region i s studied using a three-dimensional general circulation model with a L agrangian particle module. Emphasis is placed on the lower troposphere by releasing numerical tracer particles in a layer near the surface w ithin the Arctic circle to mimic the potential release of aerosol part icles from the Arctic Ocean and the observed variability of Arctic haz e. This study is also intended to investigate the characteristics of t he quasi-horizontal mixing in transporting the air from high latitudes to mid- and low latitudes; a process which has extensively been studi ed mostly for the stratospheric regime. The model calculation shows th at the Lagrangian passive tracer contours can correlate well with the isentropic potential vorticity field. This indicates that the identifi ed large-scale mixing processes due to Rossby wave breaking and chaoti c advection in the stratosphere may also occur in the lower tropospher e.