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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #154692

Title: Solar radiation transmission through conifer canopies

item Marks, Daniel

Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 6/25/2004
Publication Date: 6/25/2004
Citation: Hardy, J.P., Melloh, R., Koenig, G., Marks, D., Winstral, A., Pomeroy, J.W., and Link.T., Agricultural and Forest Meteorology, 2004; Solar radiation transmission through conifer canopies, abstract: vol 126: pp 257-270

Interpretive Summary:

Technical Abstract: Snow modeling in forests must account for the variability in snowcover and the large variations in energy transfer components at the snow surface. The purpose of this study is twofold:1)to present a novel technique to measure winter radiation around a single lodgepole pine (Pinus Contorta) tree, and 2) to evaluate the relative vertical short and longwave radiative fluxes with respect to tree geometry and implications for snow modeling. We conducted our field investigation during winter 2002 at the Local Scale Observation Site (LSOS) in Fraser, Colorado, USA as part of the Cold Land Processes Mission. At the LSOS, the managed forest is predominately lodgepole pine with some englemann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa). One pine, labeled tree 21, is in a sparse stand at 6.8 m tall, with a crown diameter of 4.7 m, and a crown height approximately 0.2 m from the ground. In February 2002, we used eight short-wave radiometers and two sets of paired radiometers (one shortwave and one longwave) to measure solar radiation at the snow surface, one two meters from the tree trunk in the north, east, south, and west directions. The paired radiometers measured incoming all-wave radiation on the south side of the tree trunk and in a canopy gap. In March 2002, we relocated the eight radiometers to the branches between 0.9 and 3.2 m above the ground, 0.2 to 1.45 m from the tree trunk, and in all orientations. The paired radiometers measured all-wave radiation on the north and south sides of the tree trunk. Variability of total receipt of incoming solar radiation around the tree during the February campaign ranged from 18.1 to 33.9m MJ m-2 for the 4-day period. In March the variability ranged from 20.5 to 63.3 MJ m-2 for the 5-day period. Preliminary results from both the February and March campaigns show that cumulative radiation more closely correlated with distance from the tree trunk (r2=0.36 and r2=0.80 respectively) than with orientation relative to the trunk (r2=0.17 and r2=0.18 respectively). In March the paired radiometers measuring all-wave radiation at the tree trunk showed little variation between the north and south sides of the trunk.