Characteristics of colliding sea breeze gravity current fronts: a laboratory study

TitleCharacteristics of colliding sea breeze gravity current fronts: a laboratory study
Publication TypeJournal Article
Year of Publication2017
Authorsvan der Wiel K., Gille ST, Smith SGL, Linden P.F, Cenedese C.
JournalQuarterly Journal of the Royal Meteorological Society
Volume143
Pagination1434-1441
Date Published2017/04
Type of ArticleArticle
ISBN Number0035-9009
Accession NumberWOS:000402539500018
Keywordsconvection; convergence; Deep convection; density currents; flow; fluid dynamics; GFD; gravity current; initiation; inland penetration; land breeze; land breezes; layer convergence lines; peninsula; propagation; scale; sea breeze; south florida
Abstract

Sea and land breeze circulations driven by surface temperature differences between land and sea often evolve into gravity currents with sharp fronts. Along narrow peninsulas, islands and enclosed seas, sea/land breeze fronts from opposing shorelines may converge and collide and may initiate deep convection and heavy precipitation. Here we investigate the collision of two sea breeze gravity current fronts in an analogue laboratory setting. We examine these collisions by means of 'lock-exchange' experiments in a rectangular channel. The effects of differences in gravity current density and height are studied. Upon collision, a sharp front separating the two currents develops. For symmetric collisions ( the same current densities and heights) this front is vertical and stationary. For asymmetric collisions ( density differences, similar heights) the front is tilted, changes shape in time and propagates in the same direction as the heavier current before the collision. Both symmetric and asymmetric collisions lead to upward displacement of fluid from the gravity currents and mixing along the plane of contact. The amount of mixing along the collision front decreases with asymmetry. Height differences impact post-collision horizontal propagation: there is significant propagation in the same direction as the higher current before collision, independent of density differences. Collisions of two gravity current fronts force sustained ascending motions which increase the potential for deep convection. From our experiments we conclude that this potential is larger in stationary collision fronts from symmetric sea breeze collisions than in propagating collision fronts from asymmetric sea breeze collisions.

DOI10.1002/qj.3015
Short TitleQ. J. R. Meteorol. Soc.
Student Publication: 
No