Title: Buoyancy waves, density currents, and their possible roles in intensifying continental convection

Abstract: Convection is known to be more intense over land than over oceans, the reasons for which have been long debated. Recent work based on the analysis of simulated and observed convective behavior over islands suggests that the primary reason for this may be rooted in the mesoscale spatial heterogeneity that typifies land surfaces, rather than several other more commonly suggested factors. The mechanisms behind this are, however, not yet clear. One study by the author has proposed a mechanism based on mesoscale wave dynamics, yet observational and model evidence also clearly indicates that propagating gust and sea-breeze fronts are crucial triggers of convection, and their rates of propagation would not be expected to match those of the implicated waves. As part of an ongoing effort to unravel this, the dynamics of sea breeze inflows are examined more carefully. While such breezes behave very much like classical density currents when initialized in a typical but unrealistic manner, they do not when initialized and forced more realistically. This is because the continued heating underneath the sea breeze as it moves over land drives internal circulations which take up most of the energy that classically would go into the current as a whole. This explains why such currents typically are slower than predicted by simple theory. It does not, however, resolve the question of how mesoscale heterogeneity drives variations in convective intensity.

http://www.ccrc.unsw.edu.au/staff/profiles/sherwood/

Host: Marty Singh
Faculty Host: Paul O'Gorman