Mesoscale Response to a Meandering Surface Temperature Interface

Abstract

Mesoscale variation of the boundary-layer (BL) front produced by a surface temperature interface depends upon the scale of meander along that interface. For a relatively large-scale meander, the circulations are quasi two-dimensional relative to the local interface boundary, and a meander signature appears in the BL structure. For a relatively small-scale meander, alongfront blending eliminates organization about individual meanders to produce a quasi two-dimensional circulation and gradients oriented perpendicular to the mean front. The fundamental atmospheric scale controlling this transition is the mesoscale deformation radius, which depends upon the warm-side BL depth. With strong large-scale geostrophic forcing, however, the resulting alongfront advection length scale increases the meander size required to approach the large-scale limit. Large-scale meanders typically create two local maxima of vertical velocity, whereas small-scale meanders develop a single maximum on the warm side of the frontal zone. At intermediate scales, variations of the vertical velocity maximum are particularly complex when large-scale geostrophic winds are relatively weak.