SCALING ANALYSIS OF CURVED FRONTS - VALIDITY OF THE BALANCE-EQUATIONSAND SEMIGEOSTROPHY

Strongly curved fronts occur when the ratios of cross-front to alongfr ont horizontal velocities and scales are comparably small for an order one distance in the alongfront direction. This means that all three v elocity terms in the continuity equation contribute at leading order. The balance equations are shown to be formally accurate through two or ders in powers of the small parameter in this situation; however, the semigeostrophic equations are accurate only at leading order. Both app roximate models are accurate through two orders of magnitude if the fr ont is more weakly curved.