Kelvin-Helmholtz Billows in Sea Breezes

Coherent turbulent structures are known to occur at the head of a gravity current. In particular, for a sea-breeze front these consist of lobe-and-cleft structure along the front (produced by a convective instability) and Kelvin-Helmholtz billows behind the front (produced by a shear instability). The billows have been found in laboratory experiments, field observations and numerical models, and are important for frontal propagation, pollutant dispersal and convective initiation. However, pronounced billows do not always occur and the reasons for their appearance (or not) are unclear. In this study we use two years of surface observations to determine how likely the billows are to form under differing synoptic conditions.

Some links for this work:

Papers:

1. A paper on the dependence of billow occurence on the ambient flow

Talks:

1. A talk on the billows presented at the 2004 UWERN meeting

Other links:

1. Billows can be seen on these pictures of "fog rollers", a density current