Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 16, 9489-9504, 2016
https://doi.org/10.5194/acp-16-9489-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
29 Jul 2016
Estimation of the advection effects induced by surface heterogeneities in the surface energy budget
Joan Cuxart1, Burkhard Wrenger2, Daniel Martínez-Villagrasa1, Joachim Reuder3,4, Marius O. Jonassen3,5, Maria A. Jiménez1, Marie Lothon6, Fabienne Lohou6, Oscar Hartogensis7, Jens Dünnermann2, Laura Conangla8, and Anirban Garai9 1University of the Balearic Islands, Palma, Mallorca, Spain
2Hochschule Ostwestfalen-Lippe, Höxter, North Rhine-Westphalia, Germany
3Geophysical Institute, University of Bergen, Bergen, Norway
4Bjerknes Centre for Climate Research, Bergen, Norway
5The University Centre in Svalbard, Longyearbyen, Norway
6Centre Recherches Atmosphériques, Univ. Toulouse & CNRS, Lannemezan, France
7Wageningen University of Research, Wageningen, the Netherlands
8Universitat Politècnica de Catalunya, Manresa, Catalonia, Spain
9University of California, San Diego, California, USA
Abstract. The effect of terrain heterogeneities in one-point measurements is a continuous subject of discussion. Here we focus on the order of magnitude of the advection term in the equation of the evolution of temperature as generated by documented terrain heterogeneities and we estimate its importance as a term in the surface energy budget (SEB), for which the turbulent fluxes are computed using the eddy-correlation method. The heterogeneities are estimated from satellite and model fields for scales near 1 km or broader, while the smaller scales are estimated through direct measurements with remotely piloted aircraft and thermal cameras and also by high-resolution modelling. The variability of the surface temperature fields is not found to decrease clearly with increasing resolution, and consequently the advection term becomes more important as the scales become finer. The advection term provides non-significant values to the SEB at scales larger than a few kilometres. In contrast, surface heterogeneities at the metre scale yield large values of the advection, which are probably only significant in the first centimetres above the ground. The motions that seem to contribute significantly to the advection term in the SEB equation in our case are roughly those around the hectometre scales.

Citation: Cuxart, J., Wrenger, B., Martínez-Villagrasa, D., Reuder, J., Jonassen, M. O., Jiménez, M. A., Lothon, M., Lohou, F., Hartogensis, O., Dünnermann, J., Conangla, L., and Garai, A.: Estimation of the advection effects induced by surface heterogeneities in the surface energy budget, Atmos. Chem. Phys., 16, 9489-9504, https://doi.org/10.5194/acp-16-9489-2016, 2016.
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Estimations of the effect of thermal advection in the surface energy budget are provided. Data from the experimental campaign BLLAST, held in Southern France in summer 2011, are used, including airborne data by drones and surface-based instrumentation. Model data outputs and satellite information are also inspected. Surface heterogeneities of the order of the kilometer or larger seem to have little effect on the budget, whereas hectometer-scale structures may contribute significantly to it.
Estimations of the effect of thermal advection in the surface energy budget are provided. Data...
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