Numerical Modeling of Topographic Influences on Shallow Front Formation and Evolution: Quasi-Stationary Coastal Front

Abstract

A two-dimensional mesoscale numerical model is used to investigate to pographic influences on shallow front formation and evolution. The shallow front is idealized as a coastal front near the southeastern China coast, with the downstream topographic features including the Taiwan Strait, the Taiwan Island and the Central Mountain Range (CMR). Shallow frontogenesis near the coast occurs as a direct result of differential heating in the boundary layer for near-surface onshore ambient flow. The idealized shallow coastal front shows similar thermal structures with the lower part of Mei-Yu fronts stagnating over the southeastern China coast, indicating that differential heating for the former similarly plays the role of geostrophic deformation in frontogenesis for the latter. Although the packed frontal isentropes tend to reside over the China coast, the frontal leading updraft may advect offshore as the shear of the upper-level offshore ambient flow is present. The associated cloud band hence is not necessarily confined near the China coast. Based on the numerical control experiments, cloud development in response in the interaction processes among the moving frontal updraft, the developed land breeze over the island and the CMR is discussed.

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