How does latent cooling affect baroclinic development in an idealized framework?

Abstract

Latent cooling by evaporating or melting hydrometeors has recently been shown to contribute to the positive low-level potential vorticity (PV) anomaly below the layer of latent heating in midlatitude cyclones. While the low-level PV anomaly might be intensified by latent cooling, the influence on the overall baroclinic development remains unclear. Including both latent heating and cooling in the Eady model, this study finds that latent cooling reduces baroclinic growth. While the PV anomaly between the layers of latent cooling and heating increases for realistic heating intensities, the PV anomaly at the top of the heating layer decreases, as latent heating is weakened because of reduced vertical motion within the cyclone. Consequently, the relative contribution from diabatic heating to the generation of eddy available potential energy decreases when latent cooling is included. Thus, despite the recently emphasized role of evaporation for the low-level PV anomaly in developing cyclones, the overall effect of latent cooling is detrimental to baroclinic growth.