Fig. 7

Frontogenesis by strain. Sketch of surface-layer frontogenesis caused by a larger scale (mesoscale) deformation flow for a front (top) and dense filament (bottom) (McWilliams 2016). There is a geostrophic along-front flow and an ageostrophic secondary circulation in the cross-front plane. With finite Ro, as typical of SMCs, the downwelling and cyclonic vorticity zones are stronger than the upwelling and anticyclonic zones