Application of an LES-based surface energy fluxes correction model: options to correct local turbulent flux measurements for non-measured landscape-scale fluxes
Abstract
The lack of surface energy balance closure is one of the most crucial challenges in the measurement of biosphere-atmosphere exchange. Transport by secondary circulations cannot be captured by common eddy-covariance tower flux measurements, which is, apart from measurement errors, one of the main explanations for the observed general underestimation of turbulent fluxes. A recently developed semi-empirical model to correct for these additional landscape-scale fluxes is now available (De Roo et al. 2018, PLOS One, DOI 10.1371/journal.pone.0209022), and we discuss here the options to apply this new method to real-world long-term flux measurement sites, in this case the beech forest site DK-Sor, and the two grassland sites DE-Fen, and DE-Gwg. Specifically, we address these two questions (I) how realistic is the partitioning approach of the energy balance residual into latent and sensible heat flux fractions?, and (II) how accurate can the absolute magnitude of the correction be estimated? We discuss the prerequisites for this energy balance closure model, which are appropriate spectral corrections, the use of well-compared post-processing software, and an estimate for the boundary layer height. For the latter quantity, we compare estimates based on ceilometer measurements with a practical modelling approach which is based on on-site turbulence measurements and freely available radio-sounding data in order to determine the potential temperature gradient above the early morning boundary layer. We compare the corrected flux estimates with independent constraints referring to nearby lysimeter measurements of evapotranspiration. Special attention is given to the quantification of flux footprints in order to assess the sensitivity of the results to the flux contribution from the target land cover type. Furthermore, we attempt to generalize the method of De Roo et al. (2018) for different flux averaging operators.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B21C..07M
- Keywords:
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- 3355 Regional modeling;
- ATMOSPHERIC PROCESSES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCES;
- 0430 Computational methods and data processing;
- BIOGEOSCIENCES