A multi-scale observational study of a mesoscale vortex over the Beaufort Sea

Szeto, K.K., R.E. Stewart, I. Halevy, J.M. Hanesiak, D.R. Hudak and R.W. Crawford

Atmos. Ocean
(Submitted)

ABSTRACT

Mesoscale vortices are rarely observed over the Beaufort Sea. Detailed observations of such a system were made during the Beaufort and Arctic Storms Experiment (BASE). Synoptic analysis, in-situ observations, satellite measurements and mesoscale model results of the system are used to provide a multi-scale perspective of the thermodynamic, kinematic and microphysical structure of the system. The mesoscale vortex formed in the center of an occluded low pressure system during the earlier hours on October 1, 1994. It developed along an enhanced baroclinic zone formed between a warm tongue associated with the occluded front and a cold tongue formed by the cold air outbreak. Satellite images showed that the vortex underwent significant scale contraction during the later hours of October 1. Multiple cloud layers were found around this vortex with cloud tops reaching 4 km in some regions and a well-defined dry air intrusion was found to wrap around the mature vortex. Saturated conditions in conjunction with a broad area of liquid water were found in the lowest levels with maximum values near 0.4 g m-3, and maximum snowfall rates were observed to be 0.5 mm h-1. There are some similarities as well as marked differences between the structure of this system and other mesoscale vortices frequently observed in high latitudes. In particular, the storm intensity and the environmental forcing of this system are relatively weak when compared to other, generally more convective, polar systems.