Do Sub‐Mesoscales Inhibit Destruction of PV?

Abstract

AbstractWe present the first explicit form of the three components, advective, diabatic, and frictional of the PV J fluxes contributed by sub‐mesoscales SM. Of particular interest is the surface value of the vertical frictional PV flux which when positive, can induce the destruction of PV by down‐front winds. The 2005 numerical simulations of Thomas confirmed that this is indeed the case. However, since the 12 km numerical resolution could not account for sub‐mesoscales SM (0.1–10) km, the effect of SM on the PV destruction process could not be quantified. The goal of this work is to provide an answer to that question asked in the title. The two SM parameterizations entering the problem, the vertical buoyancy flux and the momentum flux (Reynolds stresses), bring about a new feature, the dependence on the SM kinetic energy (represented by the dimensionless Rossby number Ro), that causes unexpected results. While in the absence of SM, there were no restrictions on where PV destruction could occur, in the presence of SM, the condition of a positive surface vertical frictional flux is restricted to SM regimes with very low Ro < 1 and very high Ro > 10. Since the SM kinetic energy is location‐dependent, so is PV destruction. The effect of SM seems to make PV destruction a much rarer occurrence than previously thought.