Diagnosis of Frontal Instabilities over the Southern Ocean

Abstract

The development of three fronts over the Southern Ocean is described using SeaWinds-on-QuikSCAT scatterometer surface winds and an attribution technique to partition the wind field in three components: nondivergent and irrotational components at the scale of the front, and the remaining harmonic component (or environmental flow) induced by the synoptic-scale flow. The front and the environment in which the front is embedded are analyzed separately. A frontal wave is shown to develop out of the first front when the large-scale alongfront stretching decreases, the environmental flow becomes frontolytic, and a connection with the upper levels is established. In the second case, the stretching remains relatively strong and no frontal wave develops. The third front exhibits a developing wave but is not in a favorable configuration with the upper levels; the frontal wave does not deepen significantly.