Four-dimensional characterization of tree canopy wetting during precipitation events

This study develops a four-dimensional (4D) Geographic Information System (GIS) model to track the movement of water through a tree canopy during a precipitation event. The goal is to understand how the wetting process of a tree canopy is correlated to spatial, temporal and environmental factors. Precipitation data at a one-minute temporal resolution was collected for a six-month period (June to November 2009) in which 20 leaf wetness sensors were installed within the canopy of a Japanese Lilac Tree on York University's Keele campus in Toronto, Ontario, Canada. Water movement varied depending on sensor position, rain category, and season. Drizzle events significantly differed compared to other rain categories and the wetness along the upper edge was significantly different from other regions of the tree canopy. These results demonstrate that the internal complexities of the tree canopy govern the heterogeneous nature of canopy wetting and drying phases.