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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2020-132
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-132
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 06 May 2020

Submitted as: research article | 06 May 2020

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This preprint is currently under review for the journal BG.

CloudRoots: Integration of advanced instrumental techniques and process modelling of sub-hourly and sub-kilometre land-atmosphere interactions

Jordi Vila-Guerau de Arellano1, Patrizia Ney2, Oscar Hartogensis1, Hugo de Boer3, Kevien van Diepen1, Dzhaner Emin4, Gesike de Groot1, Anne Klosterhalfen5, Matthias Langensiepen6, Maria Matveeva4, Gabriela Miranda1, Arnold Moene1, Uwe Rascher4, Thomas Röckmann7, Getachew Adnew7, and Alexander Graf2 Jordi Vila-Guerau de Arellano et al.
  • 1Meteorology and Air Quality Section, Wageningen University Research, 6708 PB Wageningen, the Netherlands
  • 2Institute of Bio- and Geosciences, IBG-3: Agrosphere, Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
  • 3Department of Environmental Sciences, Faculty of Geosciences, Utrecht University, the Netherlands
  • 4Institute of Bio- and Geosciences, IBG-2: Plant Sciences Forschungszentrum Jülich GmbH, 52425 Jülich, Germany
  • 5Department of Forest Ecology & Management, Swedish University of Agricultural Sciences, 90183 Umeå, Sweden
  • 6Faculty of Agriculture, University of Bonn, 53115 Bonn, Germany
  • 7Institute of Marine and Atmospheric Research Utrecht University, 3584 CC Utrecht, the Netherlands

Abstract. The CloudRoots field experiment was designed to obtain a comprehensive observational data set that includes soil, plant and atmospheric variables to investigate the interaction between a heterogeneous land surface and its overlying atmospheric boundary layer at the sub-hourly and sub–kilometre scale. Our findings demonstrate the need to include measurements at leaf level in order to obtain accurate parameters for the mechanistic representation of photosynthesis and stomatal aperture. Once the new parameters are implemented, the mechanistic model reproduces satisfactorily the stomatal leaf conductance and the leaf-level photosynthesis. At the canopy scale, we find a consistent diurnal pattern on the contributions of plant transpiration and soil evaporation using different measurement techniques. From the high frequency and vertical resolution state variables and CO2 measurements, we infer a profile of the plant assimilation that shows a strong non-linear behaviour. Observations taken by a laser scintillometer allow us to quantify the non-steadiness of the surface turbulent fluxes during the rapid changes driven by perturbation of the photosynthetically active radiation (PAR) by clouds, the so-called cloud flecks. More specifically, we find two-minute delays between the cloud radiation perturbation and ET. The impact of surface heterogeneity was further studied using ET estimates infer from the sun-induced fluorescence data and show small variation of ET in spite of the plant functional type differences. To study the relevance of advection and surface heterogeneity on the land-atmosphere interaction, we employ a coupled surface-atmospheric conceptual model that integrates the surface and upper-air observations taken at different scales: from the leaf-level to the landscape. At the landscape scale, we obtain the representative sensible heat flux that is consistent with the evolution of the boundary-layer depth evolution. Finally, throughout the entire growing season, the wide variations in stomatal opening and photosynthesis lead to large variations of plant transpiration at the leaf and canopy scales. The use of different instrumental techniques enables us to compare the total ET at various growing stages, from booting to senescence. There is satisfactory agreement between evapotranspiration of total ET, but the values remain sensitive to the scale at which ET is measured or modelled.

Jordi Vila-Guerau de Arellano et al.

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Jordi Vila-Guerau de Arellano et al.

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Short summary
The CloudRoots field experiment was designed to obtain a comprehensive observational data set that includes soil, plant and atmospheric variables to investigate the interaction between a heterogeneous land surface and its overlying atmospheric boundary layer, including the cloud effects. Our findings demonstrate that in order to understand and to represent the diurnal variability, we need to measure and model processes from the leaf to the landscape scales.
The CloudRoots field experiment was designed to obtain a comprehensive observational data set...
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