Vertical variability and effect of stability on turbulence characteristics down to the forest floor of a pine forest.

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Vertical variability and effect of stability on turbulence characteristics down to the forest floor of a pine forest. / Launiainen, S; Vesala, T; Mölder, Meelis; Mammarella, I; Smolander, S; Kolari, P; Rannik, U; Hari, P; Lindroth, Anders.

In: Tellus. Series B: Chemical and Physical Meteorology, Vol. 59, 2007, p. 919-936.

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T1 - Vertical variability and effect of stability on turbulence characteristics down to the forest floor of a pine forest.

AU - Launiainen, S

AU - Vesala, T

AU - Mölder, Meelis

AU - Mammarella, I

AU - Smolander, S

AU - Kolari, P

AU - Rannik, U

AU - Hari, P

AU - Lindroth, Anders

PY - 2007

Y1 - 2007

N2 - Among the fundamental problems in canopy turbulence, particularly near the forest floor, remain the local diabatic effects and linkages between turbulent length scales and the canopy morphology. To progress on these problems, mean and higher order turbulence statistics are collected in a uniform pine forest across a wide range of atmospheric stability conditions using five 3-D anemometers in the subcanopy. The main novelties from this experiment are: (1) the agreement between second-order closure model results and measurements suggest that diabatic states in the layer above the canopy explain much of the modulations of the key velocity statistics inside the canopy except in the immediate vicinity of the trunk space and for very stable conditions. (2) The dimensionless turbulent kinetic energy in the trunk space is large due to a large longitudinal velocity variance but it is inactive and contributes little to momentum fluxes. (3) Near the floor layer, a logarithmic mean velocity profile is formed and vertical eddies are strongly suppressed modifying all power spectra. (4) A spectral peak in the vertical velocity near the ground commensurate with the trunk diameter emerged at a moderate element Reynolds number consistent with Strouhal instabilities describing wake production.

AB - Among the fundamental problems in canopy turbulence, particularly near the forest floor, remain the local diabatic effects and linkages between turbulent length scales and the canopy morphology. To progress on these problems, mean and higher order turbulence statistics are collected in a uniform pine forest across a wide range of atmospheric stability conditions using five 3-D anemometers in the subcanopy. The main novelties from this experiment are: (1) the agreement between second-order closure model results and measurements suggest that diabatic states in the layer above the canopy explain much of the modulations of the key velocity statistics inside the canopy except in the immediate vicinity of the trunk space and for very stable conditions. (2) The dimensionless turbulent kinetic energy in the trunk space is large due to a large longitudinal velocity variance but it is inactive and contributes little to momentum fluxes. (3) Near the floor layer, a logarithmic mean velocity profile is formed and vertical eddies are strongly suppressed modifying all power spectra. (4) A spectral peak in the vertical velocity near the ground commensurate with the trunk diameter emerged at a moderate element Reynolds number consistent with Strouhal instabilities describing wake production.

U2 - 10.1111/j.1600-0889.2007.00313.x

DO - 10.1111/j.1600-0889.2007.00313.x

M3 - Article

VL - 59

SP - 919

EP - 936

JO - Tellus, Series B: Chemical and Physical Meteorology

JF - Tellus, Series B: Chemical and Physical Meteorology

SN - 0280-6509

ER -