Rain-on-snow in the Eastern United States and associated surface energy budget and atmospheric circulation

Synoptic-scale atmospheric circulation can play a role in establishing dominant surface energy budget terms during large snow ablation events. This thesis links circulation with the energy budget during snow ablation that occurs during rainfall, i.e. rain-on-snow (ROS). First, several ROS identification criteria are compared to show variability across the eastern U.S. in order to establish a regional climatology of ROS events. Findings show variability in seasonal maximum and minimum ROS frequency depend on the criteria used. Second, the attributes of synoptic types, as derived from the Temporal Synoptic Index, are compared for ROS events. Results show the importance of sensible and latent heat advection. A one-dimensional snowpack model (SNTHERM) is used to model energy budget terms across common synoptic types. The sensitivity of the energy budget to rainfall is assessed, and results show the importance of changes in the snowpack thermal structure on heat introduced from the ground.