The Integrated Effect of Condensation in Numerical Simulations of Extratropical Cyclogenesis

Abstract By combining traditional sensitivity studies with techniques that focus on the conservation and invertibility properties of Ertel's potential vorticity (PV), we illustrate the effect of latent heating on the structure and evolution of three simulated extratropical cyclones. The cases include one continental cyclone development (15 December 1987), which we examine extensively, and two cyclones over the western Atlantic Ocean (6 January 1983 and 5 January 1985) of somewhat greater intensity, which are diagnosed to assess the generality of our findings for the continental case. Each storm featured a weaker cyclonic low-level circulation when latent heating was removed from the simulation, but the magnitude of the effect varied greatly. In all cases, the difference in intensity was attributed to velocities associated with a positive, condensation-produced PV anomaly above the warm front. The amplification of the surface thermal perturbations was not strongly altered in even the case most affected by ...