Modelling of snow interception on a Japanese cedar canopy based on weighing tree experiment in a warm winter region

Snow interception by tree canopy affects the water and energy budgets. Several snow interception models have been proposed to estimate the temporal change of intercepted snow on the tree canopy from meteorological data. However, most models are based on a few observational results at limited sites or some conceptual understandings and assumptions; they still need more observational evidence and more detailed descriptions in the parameterization model for snow accumulation and snow unloading response to various meteorological conditions. A weighing tree experiment that measures the intercepted snow on the cut Japanese cedar trees was conducted in Tokamachi, Japan, to investigate the relationship between meteorological conditions and the change of intercepted snow. The results showed that the interception efficiency, which shows the ratio of intercepted snow to the total precipitation, increased with increasing air temperature in the range from −4.2 to 0°C due to increased adhesion and cohesion of snow. The maximum interception capacity was not present in observations such as an air temperature range. The unloading of intercepted snow from the canopy induced by snowmelt was related to air temperature, solar radiation, and intercepted snow amount. The snow unloading caused by wind‐blowing intercepted snow off the tree, started to develop at wind speeds exceeding 0.8 m s−1. The wind‐induced snow unloading rate coefficient increased as the wind speed increased. This study proposed a new parameterization model of snow interception based on these observations. It is the only snow interception model to use solar radiation in the snow unloading parameterization. It found that simulated and observed temporal changes of intercepted snow correlated well. Nevertheless, there were significant errors between the simulated and observed intercepted snow on several snowfall events because the model could not accurately assess the occurrence of snow unloading due to snowmelt. The tree canopy partially intercepts snowfall in the forest. This study investigated the relationship between meteorological conditions and the behaviour of intercepted snow on the tree canopy through direct observation of intercepted snow on the tree canopy in the warmer winter region. We proposed a new parameterization model for snow interception and unloading based on observational results.