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Mathias W. Rotach, Georg Wohlfahrt, Armin Hansel, Matthias Reif, Johannes Wagner, and Alexander Gohm

Among the processes contributing to the global CO2 budget, net uptake by the land surface bears the largest uncertainty. Therefore, the land sink is often estimated as the residual from the other terms that are known with greater certainty. On average over the last decades, the difference between modeled land surface uptake and this residual is negative, thus suggesting that the different modeling approaches miss an important part in land–atmosphere exchange. Based on experience with atmospheric modeling at high resolution, it is argued that this discrepancy is likely due to missed mesoscale (thermally or dynamically forced) circulations in complex terrain. Noting that more than 50% of the land surface qualifies as complex terrain, the contribution of mesoscale circulations is hypothesized to alleviate at least partly the uncertainty in the modeled land surface uptake. While atmospheric models at coarse resolution (e.g., for numerical weather prediction; also climate simulations) use a parameterization to account for momentum exchange due to subgrid-scale topography, no such additional exchange is presently taken into account for energy or mass. It is thus suggested that a corresponding parameterization should be developed in order to reduce the uncertainties in the global carbon budget.

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B. Wolf, C. Chwala, B. Fersch, J. Garvelmann, W. Junkermann, M. J. Zeeman, A. Angerer, B. Adler, C. Beck, C. Brosy, P. Brugger, S. Emeis, M. Dannenmann, F. De Roo, E. Diaz-Pines, E. Haas, M. Hagen, I. Hajnsek, J. Jacobeit, T. Jagdhuber, N. Kalthoff, R. Kiese, H. Kunstmann, O. Kosak, R. Krieg, C. Malchow, M. Mauder, R. Merz, C. Notarnicola, A. Philipp, W. Reif, S. Reineke, T. Rödiger, N. Ruehr, K. Schäfer, M. Schrön, A. Senatore, H. Shupe, I. Völksch, C. Wanninger, S. Zacharias, and H. P. Schmid

Abstract

ScaleX is a collaborative measurement campaign, collocated with a long-term environmental observatory of the German Terrestrial Environmental Observatories (TERENO) network in the mountainous terrain of the Bavarian Prealps, Germany. The aims of both TERENO and ScaleX include the measurement and modeling of land surface–atmosphere interactions of energy, water, and greenhouse gases. ScaleX is motivated by the recognition that long-term intensive observational research over years or decades must be based on well-proven, mostly automated measurement systems, concentrated in a small number of locations. In contrast, short-term intensive campaigns offer the opportunity to assess spatial distributions and gradients by concentrated instrument deployments, and by mobile sensors (ground and/or airborne) to obtain transects and three-dimensional patterns of atmospheric, surface, or soil variables and processes. Moreover, intensive campaigns are ideal proving grounds for innovative instruments, methods, and techniques to measure quantities that cannot (yet) be automated or deployed over long time periods. ScaleX is distinctive in its design, which combines the benefits of a long-term environmental-monitoring approach (TERENO) with the versatility and innovative power of a series of intensive campaigns, to bridge across a wide span of spatial and temporal scales. This contribution presents the concept and first data products of ScaleX-2015, which occurred in June–July 2015. The second installment of ScaleX took place in summer 2016 and periodic further ScaleX campaigns are planned throughout the lifetime of TERENO. This paper calls for collaboration in future ScaleX campaigns or to use our data in modelling studies. It is also an invitation to emulate the ScaleX concept at other long-term observatories.

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