Influence of surface drag on the evolution of fronts

Abstract

The approach is based on the analyses using a primitive equation model, with the domain restricted to a sector of one hemisphere, and the physics reduced to surface drag, horizontal diffusion, and dry convective adjustment. The model horizontal resolution is 1.2° latitude × 1.5° longitude, and there are 21 layers in the vertical. Shallow bent-back warm fronts develop in simulations with surface drag coefficients that are zero or representative of ocean surfaces. Warm frontogenesis is enhanced in simulations with relatively low surface drag through a feedback process involving vorticity, deformation, convergence, and warm-air advection. Surface drag tends to inhibit warm frontogenesis by decreasing the low-level wind speed and reducing the contribution of warm advection to the feedback. Consistently, a distinct warm front does not develop in the simulation with a surface drag coefficient representative of continental surfaces. Cold frontogenesis, on the other hand, is not very sensitive to surface drag. -from Authors