Simulating the impact of wind and radiation on snow dynamics across linear disturbances in boreal forests

• Main Author: Milodowski, Rosa L.
• Other Authors: Essery, Richard, Patenaude, Genevieve, Myers-Smith, Isla, Natural Environment Research Council (NERC)
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: The University of Edinburgh 2023
• Subjects: boreal forests; snow cover; linear clearings; wind flow patterns; FMI-ARC; canopy drag; snowmelt patterns; Arctic; Climate change; Northern Finland
• Online Access: https://hdl.handle.net/1842/39806; https://doi.org/10.7488/era/3054

Boreal forests are Earth‘s second largest forest biome, covering an area of 12.0–14.7 million km2. Winters are typically long, cold and dry, creating ideal conditions for sustaining snowpacks throughout this period. The spatial and temporal distribution of snow cover in boreal forest environments plays a crucial role in hydrological and ecological processes at local and regional scales. The dynamics of snow accumulation and melt reflect the interplay between such processes as the wind-driven redistribution of snow and the net energy balance at the snowpack surface. The presence of a forest canopy exerts a modifying effect on these processes; snow on the forest floor is typically sheltered from wind and direct solar radiation, whilst receiving enhanced longwave radiation from the surrounding canopy. However, the balance between these effects can be complex, particularly in the case of discontinuous forest canopies where clearings allow wind and light to penetrate down to the underlying snowpack. Understanding how the interplay between environmental factors drives spatially and temporally varying patterns of snow cover across forest edges is of particular importance and relevance in boreal regions where rates of climate change are high and forest fragmentation is increasing. In this thesis I explore how linear clearings, such as roads and tracks, may alter patterns of wind flow and incoming radiation, and consequently modify the dynamics of snow accumulation and melt across discontinuous forest canopies. This investigation uses field data collected during this research project and observations from long-running monitoring at the Arctic Research Centre of the Finnish Meteorological Institute (FMI-ARC), in northern Finland. Using a Met Office wind flow model (BLASIUS) I simulate patterns of wind flow across forest discontinuities and show that the clearing width is a key influence on these dynamics. There is less drag on the wind flow within the clearing relative to the forest canopy. Sufficient distance (approx. ...