HR: 0800h
AN: C21A-1073    [Abstracts]
TI: Small-scale spatial variability of sub-canopy radiant energy during snowmelt in deciduous and coniferous forest patches
AU: * Link, T E
EM: tlink@uidaho.edu
AF: University of Idaho, College of Natural Resources 975 W. 6th Street, Moscow, ID 83844-1133 United States
AU: Reba, M L
EM: mreba@nwrc.ars.usda.gov
AF: University of Idaho, College of Engineering 800 Park Blvd., Ste. 105, Boise, ID 83712
AU: Essery, R I
EM: rie@aber.ac.uk
AF: University of Wales, Centre for Glaciology Institute of Geography and Earth Sciences, Aberystwyth, SY23 3DB United Kingdom
AU: Hardy, J P
EM: jhardy@crrel41.crrel.usace.army.mil
AF: Cold Regions Research and Engineering Laboratory, USACE 72 Lyme Road, Hanover, NH 03755-1290 United States
AU: Marks, D
EM: dmarks@nwrc.ars.usda.gov
AF: USDA Agricultural Research Service, 800 Park Blvd., Ste. 105, Boise, ID 83712 United States
AU: Pomeroy, J W
EM: pomeroy@usask.ca
AF: University of Saskatchewan, Centre for Hydrology 117 Science Place, Saskatoon, SK S7N 5C8 Canada
AB: In mountainous, forested environments, snowcover dynamics exert a strong control on hydrologic and atmospheric processes. Snowcover ablation patterns in forests are controlled by a complex combination of depositional patterns coupled with radiative and turbulent heat flux patterns related to topographic and canopy cover variations. Quantification of small-scale variations of radiant energy in forested environments is necessary to understand how canopy structure affects snowcover energetics to improve spatially-explicit physically-based snowmelt models. Incoming solar and thermal radiation patterns were measured during the melt season around individual trees in isolated deciduous and coniferous forest patches. During clear to partly cloudy conditions, solar radiation around the leafless deciduous tree was reduced by 68%, whereas thermal radiation was enhanced by 26%. Under similar meteorological conditions, solar radiation was reduced by 87% and thermal radiation was enhanced by 43% beneath the crown of the coniferous tree. To assess potential impacts of radiative differences between open and sub-canopy net snowcover radiation, a simple analysis of sensitivity of net snowcover radiation to a range of snowcover albedo values was completed. For the meteorological conditions during this study, the analysis indicates that the deciduous canopy is likely to have a minor impact on net radiation differences. The area beneath the coniferous crown is expected to exhibit enhanced net radiation for relatively high (>0.6) open site albedo values. A small forest gap is expected to exhibit minimal difference relative to open sites for typical albedo values, whereas a large gap is expected to exhibit less net radiation than open areas. During cloudy to overcast conditions, net radiation at all canopy locations is expected to be lower than at open sites. These net radiation differences coupled with decreased turbulent fluxes due to lower wind velocities and reduced snow water equivalent values due to canopy interception losses help to explain small-scale patterns of snowmelt in non-uniform forested areas. This work also emphasizes the need to consider canopy heating in sparse forest and edge environments and to develop an improved understanding of sub-canopy snowcover albedo patterns and dynamics.
DE: 0700 CRYOSPHERE (4540)
DE: 0736 Snow (1827, 1863)
DE: 0740 Snowmelt
DE: 1813 Eco-hydrology
SC: Cryosphere [C]
MN: Fall Meeting 2005