Publications

NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.

2020

2019

To document

Abstract

The notion of the Anthropocene does not fit well into the frame of scientific disciplines. The proposed onset of a new geological epoch has become closely linked with human history and with notions such as purposeful human actions. Purposefulness, however, is also subject to interpretation in the humanities and does not fit into analytical methods in Earth sciences. Scholars have taken up this challenge and engage with Earth scientists in public discourse on the Anthropocene. Due to the lack of a common frame of reference, discussions suffer from incompatible abstractions, notions, methods and results. Here, we propose an abstract model-framework facilitating communication between Earth scientists and scholars. In Earth sciences, models are often employed to provide a representation of an independent reality which imposes limits to growth. In the humanities, self-reference and reflexivity of modernity at all scales including the globe becomes a key issue. In the former view models can be decomposed and locally tested, in the latter models and concepts involving human action need to be considered in all their contextual and semantic relations. Typically, such concepts, for example in anthropology, do not come in a mathematical language. Nevertheless, we suggest that a common reference can be sought in an abstract model language, rather than in realistic models. Category theory and formal notions developed in computer science may provide such an abstract framework to accommodate the apparently incompatible views of models and concepts, which are considered as successful by their respective home disciplines. Diverse models such as examples from game theory (economics), from dynamic system theory (Earth science) and from a classification of ethnocosmologies (anthropology) can be formulated as different instances within a joint and abstract framework. Such a framework allows to investigate implications of the Anthropocene for logical similarities with past environmental events by seeking historical analogies (for example with the great oxygenation event) or formulating consistency requirements for the future (for example by defining sustainability). The prize for the common basis is a strict ‘epistemic hygiene’, avoiding most ontological assumptions and criticisms which often appear as dear to Earth scientists and scholars, but which may prevent a more fruitful exchange on an urgent interdisciplinary topic

To document

Abstract

Preferential flow may become significant in partially frozen soils because infiltration can occur through large, initially air-filled pores surrounded by a soil matrix with limited infiltration capacity. The objectives of this study were to develop and evaluate a dual-permeability approach for simulating water flow and heat transport in macroporous soils undergoing freezing and thawing. This was achieved by introducing physically based equations for soil freezing and thawing into the dual-permeability model MACRO. Richards’ equation and the heat flow equation were loosely coupled using the generalized Clapeyron equation for the soil micropore domain. Freezing and thawing of macropore water is governed by a first-order equation for energy transfer between the micropore and macropore domains. We assumed that macropore water was unaffected by capillary forces, so that water in macropores freezes at 0°C. The performance of the model was evaluated for four test cases: (i) redistribution of water in the micropore domain during freezing, (ii) a comparison between the first-order energy transfer approach and the heat conduction equation, (iii) infiltration and water flow in frozen soil with an initially air-filled macropore domain, and (iv) thawing from the soil surface during constant-rate rainfall. Results show that the model behaves in accordance with the current understanding of water flow and heat transport in frozen macroporous soil. To improve modeling of water and heat flow in frozen soils, attention should now be focused on providing experimental data suitable for evaluating models that account for macropore flow.

To document

Abstract

Synthetic Aperture Radar (SAR) data have gained interest for a variety of remote sensing applications, given the capability of SAR sensors to operate independent of solar radiation and day/night conditions. However, the radiometric quality of SAR images is hindered by speckle noise, which affects further image processing and interpretation. As such, speckle reduction is a crucial pre-processing step in many remote sensing studies based on SAR imagery. This study proposes a new adaptive de-speckling method based on a Gaussian Markov Random Field (GMRF) model. The proposed method integrates both pixel-wised and contextual information using a weighted summation technique. As a by-product of the proposed method, a de-speckled pseudo-span image, which is obtained from the least-squares analysis of the de-speckled multi-polarization channels, is also produced. Experimental results from the medium resolution, fully polarimetric L-band ALOS PALSAR data demonstrate the effectiveness of the proposed algorithm compared to other well-known de-speckling approaches. The de-speckled images produced by the proposed method maintainthe mean value of the original image in homogenous areas, while preserving the edges of features in heterogeneous regions. In particular, the equivalent number of look (ENL) achieved using the proposed method improves by about 15% and 47% compared to the NL-SAR and SARBM3D de-speckling approaches, respectively. Other evaluation indices, such as the mean and variance of the ratio image also reveal the superiority of the proposed method relative to other de-speckling approaches examined in this study.