Title: The Lagrangian time scale for turbulent transport in forest canopies, determined from measured fluxe
1The Lagrangian time scale for turbulent transport
in forest canopies, determined from measured
fluxes and concentrations and modelled source
distributions
- Vanessa Haverd, Ray Leuning, David Griffith,
- Eva van Gorsel, Matthias Cuntz
- February 06, 2008
2Lagrangian Dispersion in Plant Canopies
- Dispersion Matrix, D
- Calculated using Lagrangian Dispersion theory
(e.g. LNF, Raupach 1989) - Inputs are turbulence statistics
- Standard deviation of vertical wind velocity sw
(measured) - Lagrangian Timescale TL (parameterised)
3Lagrangian Dispersion in Plant Canopies
Applications
4Parameterisations of Lagrangian Timescale, TL
5Approach(1)
6Approach(2)
7SVAT model, applied to Tumbarumba
- Multilayer canopy model (Wang and Leuning, 1998)
- Sunlit/ shaded leaf model coupling stomatal
conductance, photosynthesis and energy
partitioning - Radiation distribution in the canopy (3
wave-bands) - Recent additions
- Soil and biomass respiration rates (Keith et al.
2008) - Heat storage fluxes in the canopy air and biomass
(Haverd et al. 2007) - Multilayer soil model with coupled heat/moisture
fluxes and litter
8Measurements
- 70 m tower in 40 m temperate Eucalyptus forest
(Tumbarumba Ozflux site) - Continuous measurements at 70 m
- eddy fluxes (H, lE, CO2)
- Rnet
- upward and downward solar radiation fluxes
- met data
- Continuous temperature and water vapour profiles
- 2 week campaign (Nov 2006)
- 7 tower inlets to 2 Fourier transform infrared
spectrometers - Hourly measurements of CO2, water vapour
- Ground-based Lidar measurements of direct beam
transmission probability (Pgap) and hence foliage
density profile. (Jupp et al. 2008) - Array of 3D sonic anemometers ? sw profile,
Eulerian timescale. - Chamber measurements of CO2 and CH4 soil fluxes
(Fest et al. 2008)
9Measured Concentration Profiles
10Foliage Area Volume Density and Pgap
Jupp et al., 2008
11Hourly Net Fluxes at 70 m
12Vertical source/sink distributions
13Hourly flux partitioning between ground and
vegetation
14Turbulence Statistics from Measurements
15Functional form of TL
c1 ?8 c2 0.32 c1 0 c2 0.32 c1
7.32 c2 0.32
16Measured and Predicted Concentrations using prior
TL (Styles et al. parameterisation)
17Measured and Predicted Concentrations using
optimised TL (Styles et al. parameterisation)
18Massman and Weil parameterisation (1999)
19Measured and Predicted Concentrations using
optimised TL (Styles et al. and MW
parameterisations)
20Prior and Optimised Profiles of TL
Styles et al. Massman and Weil
Piecewise linear
21Summary
- TL required to calculate dispersion matrix
linking in-canopy source/sinks to concentrations. - High uncertainty in TL because it cannot be
measured directly - We have estimated the profile of TL using
- Hourly vertical profiles of ?, CO2, H2O
- SVAT model predictions of source/sink
distributions and uncertainites, constrained by
meaurements - Net fluxes above canopy
- Chamber measurements of CO2 ground fluxes
- Pgap from ground-based Lidar
- Result
- with c1 8.43.2 c2 0.490.05
- decreases with canopy depth
- 1.7 times higher than prior estimate based on TE
22Thank you
CMAR Vanessa Haverd Phone 02 6246
5981 Emailvanessa.haverd_at_csiro.au