Estimating the energy balance over forests including advection and horizontal flux divergence
Zusammenfassung der Projektergebnisse
One unsolved problem of the micrometeorological community is the unclosed energy balance when its components are independently measured in the field. This so-called energy balance closure gap was investigated with focus on sinks and sources (storage change terms) and on the uncertainties involved in the estimation of the available energy. The second main topic was the assessment of the non-turbulent fluxes of sensible heat and latent heat as well as the horizontal turbulent flux in case of sensible heat. These fluxes are commonly neglected as their assessment is difficult. The third main point was the comparison of advective fluxes of sensible heat and carbon dioxide with the aim to facilitate an easier assessment of the advective fluxes of carbon dioxide. Analyses were based on the ADVEX-dataset and the MORE II-dataset. For the investigated sites it could be shown that the energy balance closure improved when the storage terms were carefully considered. An inspection of the uncertainties involved in the available energy revealed that these uncertainties cannot explain the lack of energy balance closure alone. An inclusion of the non-turbulent advective fluxes of latent heat and sensible heat changed the corresponding budgets and improved the energy balance closure partly. However, residuals did not vanish. The horizontal turbulent flux divergence of sensible heat turned out to be negligible for the investigated site and time period. The comparison of the non-turbulent advective fluxes of sensible heat and carbon dioxide showed that advective fluxes of both scalars are larger during night than during day and that they both share a considerable scatter. On a mean diurnal basis, the advective fluxes of sensible heat and carbon dioxide turned out to be of opposite sign especially during night.
Projektbezogene Publikationen (Auswahl)
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(2007) Estimating the components of the sensible heat budget of a tall forest canopy in complex terrain. Bound-Layer Meteorol 123: 99-120
Moderow U, Feigenwinter C, Bernhofer C
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(2008) Comparision of horizontal and vertical advection advective CO2-fluxes at three forest sites. Agric Forest Meteorol 148: 12-24
Feigenwinter C, Bernhofer C, Eichelmann U, Heinesch B, Hertel M, Janous D, Kolle O, Lagergren F, Lindroth A, Minerbi S, Moderow U, Mölder M, Montagnani L, Queck R, Rebmann C, Vestin P, Yernaux M, Zeri M, Ziegler M, Aubinet M
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(2009) Available energy and energy balance closure at four coniferous sites across Europe. Theor Appl Climatol 98: 397-412
Moderow U, Feigenwinter C, Bernhofer C
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(2010) Advection is not the solution to the nighttime CO2 closure problem – evidence from three inherently different forests. Agric Forest Meteorol 150: 655-664
Aubinet M, Feigenwinter C, Bernhofer C, Canepa E, Lindroth A, Montagnani L, Rebmann C, Sedlak P, Van Gorsel E
