The Energy Balance Closure Problem – Introduction to a Panel
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Dept. of Micrometeorology Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009 The Energy Balance Closure Problem – Introduction to a Panel Discussion Discussion forum ∗ Energy talk THOMAS FOKEN University of Bayreuth Department of Micrometeorology Unter Mitwirkung von EVA FALGE and MATTHIAS MAUDER
Transcript of The Energy Balance Closure Problem – Introduction to a Panel
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
The Energy Balance Closure Problem –Introduction to a Panel Discussion
Discussion forum ∗ Energy talk
THOMAS FOKEN
University of BayreuthDepartment of Micrometeorology
Unter Mitwirkung von
EVA FALGE and MATTHIAS MAUDER
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Content
ProblemRecent FindingsConclusions for Energy FluxesConclusions for Trace Gas Fluxes
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
The Problem
The net radiation is always larger than the sum of the turbulent fluxes (sensible and latent) and the ground heat flux:
Typical residual are:
EHGs QQQQ ++≥*
%100...70%100*
=⋅++
s
EHG
QQQQ
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
-500
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-100
0
100
200
0 3 6 9 12 15 18 21 24UTC
ener
gy in
W m
-2
Sensible heat fluxLatent heat fluxNet radiationGround heat fluxResidual
Energy balance closure problem
Foken and Oncley (1995), Mauder et al. (2006), Oncley et al. (2007), Mauder and Foken (2006), Foken (2008)
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Recent Findings
Problems of measuring devices can be excludedThe energy storage in plants and soil is low and can be
determinedAdvection is possible reason but complicated to measure
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Influence of the Heterogeneity of the Landscape on the Energy Balance Closure
EBEX-2000 ExperimentU.S.A., CAResidual: 10-15 %
© Mauder et al. (2007)
LITFASS-2003 ExperimentGermanyResidual: 25-35%
NIMEX-1 (2004) ExperimentNigeriaResidual: 0 %
Negev desert IsraelHeusinkveld, et al. 2004Residual: 0 %
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Secondary Circulations found with LES Simulations for the LITFASS-2003 Experiment
© Kanda et al. (2004), for LITFASS-2003 Experiment, according to Uhlenbrock et al. (2004)
NIMEX-1 (2004) ExperimentNigeriaResidual: 0 %
2003/05/30, 12 UTC 2003/06/13, 12 UTC
1.3 zi
20 km
22 k
m
1.3 zi
20 km
22 k
m
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Long-term Eddy-Covariance Calculation
© Finnigan et al. (2003), Mauder & Foken (2006)
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Wavelet cross‐scalogramfor the sensible heat flux (above) and the latent heat flux (below). The data were measured with a Campbell CSAT3 and a LI‐COR LI‐7500 over the corn field near Lindenberg at 2.45 m above the zero‐plane displacement height.
Long-term Eddy-Covariance Calculation
© Mauder (2009)
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Energy Balance Closure for FLUXNET Sites
1
3
2
0.1 0.3 0.4 0.50.2Relative residual for QE data quality 1-3
Foo
tpri
nt cat
ego
ry
IT-Ren ES-LMa
NL-Loo
FR-Hes IT-Roc
IT-PTi1 IT-SRo
IL-Yat
BE-Vie
Relative uniformheterogeneitieson plot scale
Heterogeneitieson landscapescale, plot scaleoften uniform
FI-Sod DE-Tha
FootprintCategory
© Falge & Foken (2007)
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Recent Findings
Problems of measuring devices can be excludedThe energy storage in plants and soil is low and can be
determinedAdvection is possible reason but complicated to measureIn large-scale homogeneous areas the energy can be closedSecondary circulations can be a reason of the problem (area
averaging measuring techniques measures higher fluxes)Long-term averages can close the energy balanceEnergy balance closure is not related to footprint categories
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Schematic Overview of the Generation of Secondary Circulations and the Energy Balance Closure
© Foken (2008)
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Conclusion Energy Balance Closure
A heterogeneous landscape with typical heterogeneity scales of >> 100 m is a reason for secondary circulations and therefore an unclosed energy balance.For a landscape, which is homogeneous in scales >> 100 m, the energy balance can be closed. Only for this case experiments and models have equal results. The energy balance closure cannot be simply transferred to trace gas fluxes.
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Long Time Averaging
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u*, CO2 -Flux Density
Energy Flux Density [Wm-2]
Sensible, Latent, Residual
log Averaging Time [min]
Sensible Heat Flux
Latent Heat Flux
Residual
u*
CO2 Flux (*5)500 min
Energy balancedclosed !
From a students course September 2009 in Lindenberg
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Conclusion Trace Gas Fluxes
Analyzing of the forcing parameters for the trace gas fluxAnalyzing of the energy balance closure for the forcing fluxesTransferring of effects on the forcing fluxes to the trace gas fluxes……
Proposal for trace gas fluxes:Site specific calculation of the long-term averages changes for trace gas fluxes and application on the measuring data
Dept. of Micrometeorology
Atmospheric Transport and Chemistry in Forest Ecosystems, Castle of Thurnau, Germany, Oct 5 - 8, 2009
Panel Discussion
Prof. Dr. Marc AubinetProf. Dr. John FinniganProf. Dr. Thomas FokenProf. Dr. Monique LeclercDr. Matthias Mauder
