Preprints
https://doi.org/10.5194/amt-2021-126
https://doi.org/10.5194/amt-2021-126

  24 Jun 2021

24 Jun 2021

Review status: this preprint is currently under review for the journal AMT.

Options to correct local turbulent flux measurements for large-scale fluxes using a LES-based approach

Matthias Mauder1, Andreas Ibrom2, Luise Wanner1, Frederik De Roo3, Peter Brugger4, Ralf Kiese1, and Kim Pilegaard2 Matthias Mauder et al.
  • 1Institute of Meteorology and Climate Research – Atmospheric Environmental Research, Karlsruhe Institute of Technology, 82467 Garmisch-Partenkirchen, Germany
  • 2Dept. of Environmental Engineering, Technical University of Denmark (DTU), Kgs. Lyngby,2800, Denmark
  • 3Development center for weather forecasting, Norwegian Meteorological Institute, 0313 Oslo, Norway
  • 4Wind Engineering and Renewable Energy Laboratory (WiRE), École polytechnique fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland

Abstract. The eddy-covariance method provides the most direct estimates for fluxes between ecosystems and the atmosphere. However, dispersive fluxes can occur in the presence of secondary circulations, which can inherently not be captured by such single-tower measurements. In this study, we present options to correct local flux measurements for such large-scale transport based on a non-local parametric model that has been developed from a set of idealized LES runs for three real-world sites. The test sites DK-Sor, DE-Fen, and DE-Gwg, represent typical conditions in the mid-latitudes with different measurement height, different terrain complexity and different landscape-scale heterogeneity. Different ways to determine the boundary-layer height, which is a necessary input variable for modelling the dispersive fluxes, are applied, either from operational radio-soundings and local in-situ measurements for the flat site or from backscatter-intensity profile obtained from collocated ceilometers for the two sites in complex terrain. The adjusted total fluxes are evaluated by assessing the improvement in energy balance closure and by comparing the resulting latent heat fluxes with evapotranspiration rates from nearby lysimeters. The results show that not only the accuracy of the flux estimates is improved but also the precision, which is indicated by RMSE values that are reduced by approximately 50 %. Nevertheless, it needs to be clear that this method is intended to correct for a bias in eddy-covariance measurements due to the presence of large-scale dispersive fluxes. Other reasons potentially causing a systematic under- or overestimation, such as low-pass filtering effects and missing storage terms, still need to be considered and minimized as much as possible. Moreover, additional transport induced by surface heterogeneities is not considered.

Matthias Mauder et al.

Status: open (until 19 Aug 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-126', Anonymous Referee #2, 23 Jul 2021 reply

Matthias Mauder et al.

Matthias Mauder et al.

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Short summary
Turbulent flux measurements suffer from a general systematic underestimation. One reason for this bias is non-local transport by large-scale circulations. A recently developed model for this addition transport of sensible and latent energy is evaluated for three different test sites. Different options on how to apply this correction are presented and the results are evaluated against independent measurements.