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Gradient distributions and flux profile relations above a rough forest
Author(s) -
Lindroth A.
Publication year - 1984
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49711046415
Subject(s) - evapotranspiration , bowen ratio , flux (metallurgy) , fetch , humidity , energy balance , temperature gradient , environmental science , atmospheric sciences , sensible heat , energy flux , mathematics , physics , meteorology , geology , materials science , ecology , thermodynamics , oceanography , biology , astronomy , metallurgy
Temperature and humidity gradients above a sparse pine forest (400 trees per hectare) in Sweden were measured using movable sensors. Under daytime conditions the gradients were remarkably small with a median value of −0.007 K m −1 for the potential temperature gradient and −3.8 × 10 −6 m −1 for the specific humidity gradient. The range of inferred Bowen ratios was −0.3 to 1.8 with a median value of 0.72. The starting point for the paper was a discrepancy between energy balance/Bowen ratio (EBBR) and water balance estimates of the forest evapotranspiration. There was no sign that insufficient fetch influenced the results but some evidence was obtained to suggest that the lowest measurement level, about one mean distance between trees above the mean tree level, was situated in a region of inhomogeneity in the heat and water flux field. Excluding this level from the calculations increased the inferred Bowen ratio by 30%. This change is not sufficient to account for the difference in estimates of evapotranspiration by the two methods. It is, however, concluded that the discrepancy could be explained by rather small, quite realistic errors in the gradient measurements.