A Relationship of Isentropic Back Trajectories with Observed Wind Direction and Synoptic Type in the North Atlantic

Abstract

A spring season sample of isentropic back trajectories for the North Atlantic region is presented. The sample data, derived from select time periods during four spring seasons, are used to investigate the relationship of three-dimensional trajectories with observed wind direction and synoptic type. The trajectory data show a predominance of transport from the west and suggest that three-dimensional air motions in the midlatitude regions have a pronounced vertical component whose direction and magnitude are significantly related to the transport direction. Statistical results indicate that the observed wind direction and synoptic type can be used to derive a reasonably good estimate of the mean transport direction for an ensemble of 36-h or 72-h trajectories. However, neither of them provides a good estimate of the transport direction for individual trajectories. The results also show that the mean vertical and horizontal displacements of the trajectory air parcels are not strongly related to observed wind direction or synoptic type.