Hot Trees : measurement and modelling of sub-canopy longwave radiation to seasonnal snow.
Jeudi 12 jan. 2017 à 13 h : séminaire de Clare Webster (SLF/WSL, Davos) et Nick Rutter (Northumbria University, UK), salle de réunion OSUG-B 1er étage
Modelling energy balance interactions between forests and the sub-canopy snow surface requires an improved understanding of how trees absorb and emit radiation. This is important as the retreat of springtime Northern Hemisphere snowmelt is currently underestimated by land-surface models. The cause of this underestimation is uncertain, especially whether or not it is due to an insufficient parameterisation of sub-canopy energy and mass balance processes or an absence / structural incompatibility of the processes themselves. Consequently, improved measurement and parameterisation of longwave energy exchanges in forests of differing plant functional type and variable density is of crucial importance. Recent studies have presented improvements in model estimations at the point scale by replacing air temperature with measured forest temperature - shown to be at times distinctly higher than air temperatures. To further investigate parameterisations of longwave energy exchanges, in-situ meteorological, tree temperature and forest canopy structure measurements are presented from Arctic European snow-covered boreal forests and Swiss alpine forests. Data collection techniques combine traditional radiation sensor arrays, as well as terrestrial and airborne laser scanning, thermal imagery and Unmanned Aerial Vehicles (UAVs).