Relative quantification of wind erosion in argan woodlands in the Souss Basin,Morocco

The endemic argan woodlands cover large parts of South Morocco and create a characteristic landscape with areas of sparsely vegetated and bare soil surfaces between single trees. This unique ecosystem has been under extensive agrosilvopastoral management for centuries and is now at risk of degradation caused by overgrazing and increasing scarcity and variability of rainfall. To investigate susceptibility to wind erosion, we conducted an experimental–empirical study including wind tunnel tests and a drone-generated digital elevation model and quantified wind-erodible material on five different associated surface types by means of sediment catchers. The highest emission flux was measured on freshly ploughed surfaces (1875 g m^–2 h^–1), while older ploughed areas with a re-established crust produced a much lower emission flux (795 g m^–2 h^–1). Extensive tillage may have been a sustainable practice for generations, but increasing drought and uncertainty of rainfall now lead to an acute risk of severe soil erosion and dust production. The typical crusted surfaces characterized by residual rock fragment accumulation and wash processes produced the second highest emission flux (1,354 g m^–2 h^–1). Material collected from tree-shaded areas (933 g m^–2 h^–1) was revealed to be a considerable source of organic material, possibly affecting substrate conditions positively on a larger regional scale. The lowest flux was measured on rock fragment-covered surfaces (301 g m^–2 h^–1). The data show that open argan woodland may be a considerable source for wind erosion and dust production, depending on surface characteristics strongly related to management. An adapted management must include the conservation of argan trees to offer a promising approach to prevent severe wind erosion and dust production and mitigate possible impacts of land-use change and climate change related shifts in wind and rainfall patterns. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

Displacement-based seismic design of buildings with thin reinforced concrete structural walls with a single curtain of welded wire mesh

Bulletin of Earthquake Engineering - In past decades, multistory housing buildings have been constructed in high-seismic-risk regions in Latin America using thin reinforced concrete (RC) walls as...     

Eruptive history and petrologic evolution of the Albano multiple maar (Alban Hills, Central Italy)

A comprehensive volcanological study of the Albano multiple maar (Alban Hills, Italy) using (i) ⁴⁰Ar/³⁹Ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and (ii) petrographic observations, phase analyses of major and trace elements, and Sr and O isotopic analyses of the pyroclastic deposits shows that volcanic activity at Albano was strongly discontinuous, with a first eruptive cycle at 69±1 ka producing at least two eruptions, and a second cycle with two peaks at 39±1 and 36±1 ka producing at least four eruptions. Contrary to previous studies, we did not find evidence of magmatic or hydromagmatic eruptions younger than 36±1 ka. The activity of Albano was fed by a new batch of primary magma compositionally different from that of the older activity of the Alban Hills; moreover, the REE and ⁸⁷Sr/⁸⁶Sr data indicate that the Albano magma originated from an enriched metasomatized mantle. According to the modeled liquid line of descent, this magma differentiated under the influence of magma/limestone wall rock interaction. Our detailed eruptive and petrologic reconstruction of the Albano Maar evolution substantiates the dormant state of the Alban Hills Volcanic District. Electronic Supplementary Material Supplementary material is available for this article at Editorial responsibility: J. Donnelly-Nolan An erratum to this article can be found at     

Multi-year drought frequency analysis at multiple sites by operational hydrology - A comparison of methods

This paper compares two generators of yearly water availabilities from sources located at multiple sites with regard to their ability to reproduce the characteristics of historical critical periods and to provide reliable results in terms of the return period of critical sequences of different length. The two models are a novel multi-site Markov mixture model explicitly accounting for drought occurrences and a multivariate ARMA. In the case of the multisite Markov mixture model parameter estimation is limited to a search in the parameter space guided by the value of parameter λ to show the sensitivity of the model to this parameter. Application to two of the longest time series of streamflows available in Sicily (Italy) shows that the models can provide quite different results in terms of estimated return periods of historic droughts, although they seem to perform more uniformly when it comes to simulate drought-related statistics such as drought length, severity and intensity. The role of parameter selection for the multisite Markov mixture model and of the marginal probability of generated flows in providing results consistent with the characteristics of the observed series is discussed. Both models are applied to the system of sources supplying the city of Palermo (Sicily) and its environs showing the applicability of the newly developed multisite Markov mixture model to medium-to-large scale water resources systems.     

Variazioni del moto polare della Terra e loro correlazioni meteorologiche

Riassunto Vengono documentate ed illustrate alcune correlazioni fra le alterazioni del moto di rotazione terrestre iniziatesi nel 1923 con gli eventi meteorologici; in particolare si discutono e si spiegano in tal modo le forti anomalie della pressione osservate a Genova nel periodo 1924–32.

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Zusammenfassung Störungen in der Bewegung des Erdkörpers und Verschiebungen seiner Rotaktionsachse rufen Wirkungen hervor, welcke mit der Anpassung der Luftmassen an den neuen Bewegungen und an den neuen Lagen der Rotaktionsachse sich ausdrucken. Das führt zu Veränderungen der Luftströmungen, der Luftdruckverteilungen und daher der Grossewetterlagen. Einige meteorologischen Korrelationen dieser Art werden für die bedeutende Störung der Polarbewegung des 1923 gezeigt. Nachher werden damit besonders die starken Luftdruckanomalien erklärt, welche in Genua in der Periode 1924–32 beobachtet worden sind.

     

Using semivariogram parameter uncertainty in hydrogeological applications

Geostatistical estimation (kriging) and geostatistical simulation are routinely used in ground water hydrology for optimal spatial interpolation and Monte Carlo risk assessment, respectively. Both techniques are based on a model of spatial variability (semivariogram or covariance) that generally is not known but must be inferred from the experimental data. Where the number of experimental data is small (say, several tens), as is not unusual in ground water hydrology, the model fitted to the empirical semivariogram entails considerable uncertainty. If all the practical results are based on this unique fitted model, the final results will be biased. We propose that, instead of using a unique semivariogram model, the full range of models that are inside a given confidence region should be used, and the weight that each semivariogram model has on the final result should depend on its plausibility. The first task, then, is to evaluate the uncertainty of the model, which can be efficiently done by using maximum likelihood inference. The second task is to use the range of plausible models in applications and to show the effect observed on the final results. This procedure is put forth here with kriging and simulation applications, where the uncertainty in semivariogram parameters is propagated into the final results (e.g., the prediction of ground water head). A case study using log-transmissivity data from the Vega de Granada aquifer, in southern Spain, is given to illustrate the methodology.     

Shear partitioning in the Philippines: Constraints from Philippine Fault and global positioning system data

Abstract The Philippine Fault is a major left-lateral structure formed in an island arc setting. It accommodates a component of the oblique convergence between the Philippine Sea Plate and the Philippine archipelago. This observation is quantified through a series of global positioning satellite experiments between 1991 and 1996. The formation of the Fault marks the onset of a new geodynamic regime in the Philippine region. In the central Philippines, this event corresponds to the creation of a new tectonic boundary separating the Philippine Mobile Belt and the Philippine Sea Plate, following the latter's kinematic reorganization that occurred around 4 Ma ago. During this event, the Philippine Sea Plate changed its relative movement with respect to Eurasia from a northward to a north-westward motion, favoring the formation of a Philippine Fault–Philippine Trench system under a shear partitioning mechanism.