A downward developing mesoscale cyclone over the Ross Ice Shelf during Winter

A case of midtropospheric mesoscale cyclone formation and downward development adjacent to and over the Ross Ice Shelf, Antarctica during May 1988 is presented. This event involved atmospheric phenomena over a wide range of spatial scales from the meso to the synoptic. The mesoscale vortex apparently developed within a middle-level short-wave trough. Warm air advection associated with a synoptic-scale front, which developed upwind from the axis of a blocking ridge located over the Antarctic Peninsula and which traveled westward across West Antarctica, created a strong temperature gradient (baroclinic zone) at low-levels at the northern edge of the Ross Ice Shelf. The atmosphere below the initially midtropospheric mesoscale vortex was destablized by the warm air advection, inducing its downward development.