Microclimatic Effects of a Forest-to-Peatland Transition on Aerodynamic Resistance to Water Vapour Transfer in the Sub-h
- PDF / 3,125,462 Bytes
- 22 Pages / 439.37 x 666.142 pts Page_size
- 22 Downloads / 135 Views
Microclimatic Effects of a Forest-to-Peatland Transition on Aerodynamic Resistance to Water Vapour Transfer in the Sub-humid Boreal Plains A. Green1
· G. Bohrer2 · R. Petrone1
Received: 23 September 2019 / Accepted: 3 September 2020 © Springer Nature B.V. 2020
Abstract Peatlands often experience turbulent sheltering from their surrounding upland forests, which results in spatially variable surface–atmosphere exchanges of momentum, heat, and moisture produced by flow-separation dynamics, which suppresses the transport of such scalars in the sheltered region while promoting transport in the reattachment zone. With evapotranspiration being the dominant source of water loss in the Boreal Plains, it is necessary to understand the dynamics and controls on evapotranspiration within these peatlands. We used the regional atmospheric forest large-eddy simulation (RAFLES) model to study the impact of flow separation and surface roughness on microclimates leeward of a forest-to-peatland roughness transition. We parametrized our simulation with observed vegetation characteristics and meteorological data from three natural peatlands to accurately estimate natural ranges of peatland roughnesses and energy dynamics. Our simulations show that changes to peatland roughness do not affect the distances required for flow reattachment, and therefore the size of the sheltered region. However, increasing the surface roughness produces greater surface turbulence, quicker flow recovery, and decreased flow reversals within the sheltered region. Further, substantial microclimatic differences are observed throughout the flow regions of the roughness transition. Our results show that turbulence, aerodynamic resistance, and the microclimate vary throughout the backward-facing step transition and should be taken into account when estimating the spatial dynamics of evaporative demand leeward of a roughness transition. Furthermore, increasing the surface roughness of a peatland minimizes the spatial variability of turbulent drivers of evapotranspiration across a roughness transition. That is, flow separation and the surface roughness of the peatland should be accounted for when estimating the spatial variability and total evaporative potential across a peatland. Keywords Backward-facing step · Large-eddy simulation · Moisture transfer · Peatlands · Roughness transition
1 Introduction The Boreal Plains region of the Western Boreal Forest in Canada is a complex mosaic of wetlands and aspen-dominated uplands, where wetlands account for approximately 50% of
Extended author information available on the last page of the article
123
A. Green et al.
the natural landscape; peatlands comprise 90% of these wetlands (Vitt et al. 1996). The subhumid climate of the Boreal Plains results in persistent water deficit conditions where potential evapotranspiration is greater than precipitation on an annual basis, with wetlands being sustained by infrequent wet years on a 10–15 year cycle (Marshall et al. 1999; Devito et al. 2005). Peatlands of the Boreal Pla
Data Loading...
