Publication Date:
2022-05-25
Description:
Author Posting. © The Author(s), 2017. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Quarterly Journal of the Royal Meteorological Society 143 (2017): 1434–1441, doi:10.1002/qj.3015.
Description:
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.
Description:
National Science Foundation Grant Number: OCE-0824636;
Office of Naval Research Grant Number: N00014-09-1-0844;
National Aeronautics and Space Administration Grant Number: NASA NNX14A078G
Keywords:
Sea breeze
;
Land breeze
;
Gravity current
;
Convergence
;
Deep convection
;
GFD
;
Fluid dynamics
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
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