Doppler Radar Analysis of Vortices over the Mountains of Taiwan

Abstract

Small-scale cyclonic vortices, which were embedded within a larger, mesoscale area of cyclonically curved flow, are documented over the mountains of Taiwan during the Taiwan Area Mesoscale Experiment. The vortices are visualized in dual-Doppler radar analyses of the wind field in the region of stratiform precipitation of a decaying mesoscale convective system. Each vortex was approximately 20 km across and had a lifetime on the order of an hour. The vortices formed and decayed during a 4-h period over Taiwan's Central Mountain Range and propagated with the flow associated with the mesoscale area of cyclonically curved flow in which they were embedded. The vortices extended through a deep layer in the troposphere, but were strongest near the mountaintop level, and decayed in intensity with height. Circumstantial evidence is presented that the vortices may have formed through the interaction of the mesoscale area of cyclonic flow with a mountain ridge.