The IMPROVE-1 Storm of 1–2 February 2001. Part IV: Precipitation Enhancement across the Melting Layer

Abstract

Previous model simulations indicate that in stratiform precipitation, the precipitation rate can increase by 7% in the melting layer through direct condensation onto melting snow and the resultant cooled rain. In the present study, a model simulation of stratiform precipitation in a wide cold frontal rainband indicates that the precipitation rate can also increase by 5% in the melting layer through accretion, by melting snow and rain, of additional cloud water produced by the latent cooling of the ambient air associated with melting snow. The contribution of the combined processes, and therefore the additional precipitation gained through the latent cooling of melting snow within the melting layer, may contribute as much as 10% to the precipitation rate in stratiform precipitation.

Orographic Flow Response to Variations in Upstream Humidity

“…Enhanced condensation and production precipitate just below z fr has been observed in the real atmosphere and different theories exist to explain it. These include localized cooling due to melting and enhanced accretion on melting hydrometeors (Woods et al 2008).…”

The role of latent heating in warm frontogenesis

“…Two maxima exist in the cloud condensation and cloud nucleation fields, labelled I and II in Figure 6(d). The upper peak is due to supersaturated conditions associated with peaks in updraught velocities, while the lower peak is associated with the melting layer ( Figure 6(f)), where the latent cooling by melting is helping to create supersaturated conditions (Woods et al, 2008). Although the heat absorbed .…”