Experimental verification of downwind flux contributions and its integration in an existing flux footprint model

In the last decades flux footprint modeling has evolved to an indispensable quality assessment tool in micrometeorology. In studies which include routine footprint estimates for long-term or continuous flux observations, analytical models are the most commonly used class of footprint models, due to their mathematical simplicity, and hence their low computational expense. This practical advantage outweighs the two main drawbacks of such models: their common assumption of homogeneous turbulence, which is not usually fulfilled in practical flux measurement conditions, and the non-consideration of flux contributions from sources downwind of the measurement system. To demonstrate that downwind flux contributions are present and measurable, we conducted tracer experiments at a grassland site in Graswang, southern Germany. The site is part of the TERENO.net preAlpine observatory and is located on a flat alluvial valley bottom (ca. 1 km wide), flanked by steep sides. An artificial tracer (methane) was released continuously over one averaging period from a surface source of 1m2 size located downstream of an eddy covariance measurement system. Our measurements show that, depending on along-wind turbulence intensity σu/u̅, downwind sources can contribute considerably to a flux measurement. We introduce a new version of the existing flux footprint model FSAM (Schmid, 1994) that now takes along-wind diffusion into account and thus is capable of accounting for downwind flux contributions. A programming error that encumbered later versions of FSAM has also been corrected in the new version. Further, we are able to evaluate the overall performance of the new model by means of additional tracer experiments

Long term global trends in open access. A data paper

Studies on long term trends in open access are of interest for the assessment of the evolution of scientific publishing and related markets. We therefore compiled and analysed a data set that integrated Web of Science as a global bibliographic data source on internationally relevant publications with data from Unpaywall, the primary provider of information related to open access at publication level. Data were captured in 2021 and show the open access categories as defined by Unpaywall for the publication years 2000 to 2020. In these two decades open access has gained substantial momentum. Starting with a few per cent, it now covers roughly half of the publications when embargo periods are over. The comparison of four variants of subsets of these data, however, show the wide variability in absolute and relative numbers. Results depend heavily on the characteristics of the data sources and the subsets selected within these. Major factors are listed and discussed. Aggregated data are provided in the MPG data repository

Stress field sensitivity analysis in a sedimentary sequence of the Alpine foreland, Northern Switzerland

The stress field at depth is a relevant parameter for the design of subsurface constructions and reservoir management. Yet the distortion of the regional stress field due to local-scale features such as sedimentary and tectonic structures or topography is often poorly constrained. We conduct a stress sensitivity analysis using 3-D numerical geomechanical modelling with an elasto-plastic material law to explore the impact of such site specific features on the stress field in a sedimentary sequence of the Swiss Alpine foreland. The model\u27s dimensions are 14 km × 14 km × 3 km and it contains ten units with different mechanical properties, intersected by two regional fault zones. An initial stress state is established involving a semi-empirical relationship between the ratio of horizontal to vertical stress and the overconsolidation ratio of argillaceous sediments. The model results indicate that local topography can affect the stress field significantly to depths greater than the relief contrasts at the surface, especially in conjunction with horizontal tectonic loading. The complexity and frictional properties of faults are also relevant. The greatest variability of the stress field arises across the different sedimentary units. Stress magnitudes and stress anisotropy are much larger in stiffer formations such as massive limestones than in softer argillaceous formations. The stiffer formations essentially carry the load of the far-field forces and are therefore more sensitive to changes of the boundary conditions. This general characteristic of stress distribution in the stiff and soft formations is broadly maintained also with progressive loading towards the plastic limit. The stress field in argillaceous sediments within a stack of formations with strongly contrasting mechanical properties like in the Alpine foreland appears to be relatively insensitive to changes in the tectonic boundary conditions and is largely controlled by the maximum stiffness contrast with respect to the load-bearing formations

Present-day stress orientations and tectonic provinces of the NW Borneo collisional margin

Extent: 15p.Borehole failure observed on image and dipmeter logs from 55 petroleum wells across the NW Borneo collisional margin were used to determine maximum horizontal stress (σH) orientations; combined with seismic and outcrop data, they define seven tectonic provinces. The Baram Delta–Deepwater Fold-Thrust Belt exhibits three tectonic provinces: its inner shelf inverted province (σH is NW-SE, margin-normal), its outer shelf extension province (σH is NE-SW, margin-parallel), and its slope to basin floor compression province (σH is NW-SE, margin-normal). In the inverted province, σH reflects inversion of deltaic normal faults. The σH orientations in the extension and compression provinces reflect deltaic gravitational tectonics. The shale and minibasin provinces have been recognized in offshore Sabah. In the shale province, σH is N010°E, which aligns around the boundary of a massif of mobile shale. Currently, no data are available to determine σH in the minibasin province. In the Balingian province, σH is ESE-WNW, reflecting ESE absolute Sunda plate motions due to the absence of a thick detachment seen elsewhere in NW Borneo. The Central Luconia province demonstrates poorly constrained and variable σH orientations. These seven provinces result from the heterogeneous structural and stratigraphic development of the NW Borneo margin and formed due to complex collisional tectonics and the varied distribution and thicknesses of stratigraphic packages.Rosalind C. King, Mark R. P. Tingay, Richard R. Hillis, Christopher K. Morley, and James Clar

Impact of faults on the remote stress state

The impact of faults on the contemporary stress field in the upper crust has been discussed in various studies. Data and models clearly show that there is an effect, but so far, a systematic study quantifying the impact as a function of distance from the fault is lacking. In the absence of data, here we use a series of generic 3-D models to investigate which component of the stress tensor is affected at which distance from the fault. Our study concentrates on the far field, located hundreds of metres from the fault zone. The models assess various techniques to represent faults, different material properties, different boundary conditions, variable orientation, and the fault's size. The study findings indicate that most of the factors tested do not have an influence on either the stress tensor orientation or principal stress magnitudes in the far field beyond 1000 m from the fault. Only in the case of oblique faults with a low static friction coefficient of μ=0.1 can noteworthy stress perturbations be seen up to 2000 m from the fault. However, the changes that we detected are generally small and of the order of lateral stress variability due to rock property variability. Furthermore, only in the first hundreds of metres to the fault are variations large enough to be theoretically detected by borehole-based stress data when considering their inherent uncertainties. This finding agrees with robust stress magnitude measurements and stress orientation data. Thus, in areas where high-quality and high-resolution data show gradual and continuous stress tensor rotations of &gt;20∘ observed over lateral spatial scales of 10 km or more, we infer that these rotations cannot be attributed to faults. We hypothesize that most stress orientation changes attributed to faults may originate from different sources such as density and strength contrasts.</p

Wave-length of the crustal stress pattern in Western Europe and the Mediterranean

Oliver Heidbach, Moritz Ziegler, Mojtaba Rajabi, Karsten Reiter and the WSM Tea