Comparison of forecasting performance of nonlinear models of hydrological time series

Mean monthly flows of the Tatry alpine mountain region in Slovakia are predominantly fed by snowmelt in the spring and convective precipitation in the summer. Therefore their regime properties exhibit clear seasonal patterns. Positive deviations from these trends have substantially different features than the negative ones. This provides intuitive justification for the application of nonlinear two-regime models for modelling and forecasting of these time series. Nonlinear time series structures often have lead to good fitting performances, however these do not guarantee an equally good forecasting performance. In this paper therefore the forecasting performance of several nonlinear time series models is compared with respect to their capabilities of forecasting monthly and seasonal flows in the Tatry region. A new type of regime-switching models is also proposed and tested. The best predictive performance was achieved for a new model subclass involving aggregation operators.     

Geoarchaeological investigations of the “potters' quarter” at Sagalassos,southwest Turkey

The potters' quarter of the ancient city of Sagalassos, southwest Turkey, was one of the largest and most enduring ceramic‐producing manufactories in the eastern Mediterranean. The objective of our study was to determine environmental circumstances that favored development of different clay resources in the territory of Sagalassos and to assess utilization of these resources in the local pottery manufactory. The potters' quarter was established where, owing to favorable geological circumstances, a large clay body had developed. The bedrock in the potters' quarter, a tectonized ophiolite sequence, has synclinal structure; hence, surface runoff and groundwater tend to accumulate in its center. The weathering of the basic rock formed a smectite‐rich clay with vertic properties. This clay was mined in antiquity, and mineralogical and chemical analyses indicate that it was used for the production of local ceramics from Hellenistic to Byzantine times. It is likely that colluvium on top of the ophiolitic clay at the potters' quarter is related to deforestation and slope processes after the potters' quarter was abandoned. In sum, environmental circumstances determined the location of the artisanal quarter of Sagalassos, with its clay quarrying operation and ceramic manufactory. However, for the local mass‐produced Sagalassos red slip ware, the results of our chemical and mineralogical analyses indicate that a different, more suitable clay was used: detrital lake sediments, rich in chlorite and chlorite/smectite mixed layers, located about 8 km from the original artisanal quarter. The choice for this clay was determined both by the presence of a suitable clay deposit, as well as socio‐economic circumstances such as land ownership. The site of Sagalassos yielded unique evidence of mining of clay at a ceramic production site, as well as import of nearby clays. The local and imported clays were used side‐by‐side, but one for the production of common wares and building ceramics, and the other for the manufacturing of luxury fine tablewares. © 2003 Wiley Periodicals, Inc.     

Electromagnetic Radiation and Motion of a Particle

We consider the motion of uncharged dust grains of arbitrary shape including the effects of electromagnetic radiation and thermal emission. The resulting relativistically covariant equation of motion is expressed in terms of standard optical parameters. Explicit expressions for secular changes of osculating orbital elements are derived in detail for the special case of the Poynting-Robertson effect. Two subcases are considered: (i) central acceleration due to gravity and the radial component of radiation pressure independent of the particle velocity, (ii) central acceleration given by gravity and the radiation force as the disturbing force. The latter case yields results which may be compared with secular orbital evolution in terms of orbital elements for an arbitrarily shaped dust particle. The effects of solar wind are also presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

The environmental significance of the remobilisation of ancient mass movements in the Atbara–Tekeze headwaters, Northern Ethiopia

Old landslides are prominent features in the landscape around Hagere Selam, Tigray Highlands, Ethiopia. The available evidence suggests their Late Pleistocene to Middle Holocene age and conditions of soil humidity. The affected geological layers, often silicified lacustrine deposits prone to sliding, rest upon or above the water holding Amba Aradam sandstone aquifer.Three examples of present-day (remobilisation of old) mass movements are illustrated and discussed. The aims of the study were to unravel the environmental conditions of the present-day remobilisation of ancient flows, as well as those of first-time landslides. The first two mass movements discussed are slumps, located in areas with vigorous regeneration of (grassy) vegetation. Their activation is thought to be the consequence of an increase in infiltration capacity of the soils under regenerating vegetation. One of these slumps had a horizontal movement of the order of 10–20 m in 1 day.The other case is the remobilisation of the May Ntebteb debris flow below the Amba Aradam sandstone cliff. The debris flow presently creeps downslope at a rate of 3–6 cm year⁻¹. Palynological evidence from tufa shows that the reactivation of the flow started 70 years ago. Shear resistance measurements indicate the danger for continuous or prefailure creep. From the soil mechanics point of view, the reactivation of the debris flow is due to the combination of two factors: (1) the reduction of flow confining pressures as a result of gully incision over the last hundred years, and (2) the increase of seepage pressure as a consequence of the cumulative effect of this incision and the increase in infiltration rates on the lobe since grazing and woodcutting have been prohibited 8 years ago. The role of such exclosures as possible landslide triggers is discussed.From the geomorphological point of view, the ancient movements and their present-day reactivation cannot be compared: the ancient movements led to the development of debris flows, whereas the reactivations relate to the dissection of these mass movement deposits.     

The stratigraphic and paleoenvironmental setting of Aptian OAE black shale deposits in the Pieniny Klippen Belt, Slovak Western Carpathians

During the Jurassic and Cretaceous, the Pieniny Klippen Belt units of the Outer Western Carpathians were situated on the edge of the Paleoeuropean shelf rimming the northermost margin of the Mediterranean Tethys. During the late early Aptian humid event, Lower Cretaceous pelagic carbonate (Maiolica) sedimentation was interrupted by terrigenous input as a consequence of the first major mid-Cretaceous climate perturbations. The fluctuation of radiolarian abundance indicated an expansion of the oxygen-minimum zone due to upwelling conditions and salinity changes. Foraminifera, radiolarians, non-calcareous dinocysts, and calcareous nannofossils encountered in the West Carpathian Rochovica section enable a comparison of the black shales of the upper lower Aptian Koňhora Formation with the well-known Selli Event. Subsequent anoxia patterns (depositional, productive, and stagnant) have taken part in the depositional regime. Early Aptian climate perturbations both in the Outer Western Carpathians, Swiss Prealps (situated in a similar position on the distal southern edge of the former Paleoeuropean shelf) and/or in other parts of the world are traceable with sedimentological, biological, and chemical proxies.     

Revisiting lake sediment budgets: How the calculation of lake lifetime is strongly data and method dependent

Lake sedimentation has a fundamental impact on lake lifetime. In this paper, we show how sensitive calculation of the latter is to the quality of data available and assumptions made during analysis. Based on the collection of a large new dataset, we quantify the sediment masses (1) mobilized on the hillslopes draining towards Lake Tana (Ethiopia), (2) stored in the floodplains, (3) transported into the lake, (4) deposited in the lake and (5) delivered out from the lake so as to establish a sediment budget. In 2012–2013, suspended sediment concentration (SSC) and discharge measurements were made at 13 monitoring stations, including two lake outlets. Altogether, 4635 SSC samples were collected and sediment rating curves that account for land cover conditions and rainfall seasonality were established for the 11 river stations, and mean monthly SSC was calculated for the outlets. Effects of the floodplain on rivers' sediment yield (SY) were investigated using measurements at both sides of the floodplains. SY from ungauged rivers was assessed using a model that includes catchment area and rainfall, whereas bedload and direct sediment input from lake shores were estimated. As a result, the gross annual SY was c. 39.55 (± 0.15) Mt, dominantly from Gilgel Abay and Gumara Rivers. The 2.57 (± 0.17) Mt sediment deposited in floodplains indicate that the floodplains serve as an important sediment sink. Moreover, annually c. 1.09 Mt of sediment leaves the lake through the two outlets. Annual sediment deposition in the lake was c. 36.97 (± 0.22) Mt and organic matter accumulation was 2.15 Mt, with a mean sediment trapping efficiency of 97%. Furthermore, SSC and SY are generally higher at the beginning of the rainy season because soils in cultivated fields are bare and loose due to frequent ploughing and seedbed preparation. Later in the season, increased crop and vegetation cover lead to a decrease in sediment production. Based on the established sediment budget with average rainfall, the lifetime of Lake Tana was estimated as 764 to 1032 years, which is shorter than what was anticipated in earlier studies. The sedimentation rate of Lake Tana (11.7 ± 0.1 kg m^?2 yr^?1) is in line with the sedimentation rates of larger lakes in the world, like Lake Dongting and Lake Kivu. Copyright © 2017 John Wiley & Sons, Ltd.     

Mineralogy,petrography, geochemistry,and classification of the Košice meteorite

The Ko?ice meteorite was observed to fall on 28 February 2010 at 23:25 UT near the city of Ko?ice in eastern Slovakia and its mineralogy, petrology, and geochemistry are described. The characteristic features of the meteorite fragments are fan‐like, mosaic, lamellar, and granular chondrules, which were up to 1.2 mm in diameter. The fusion crust has a black‐gray color with a thickness up to 0.6 mm. The matrix of the meteorite is formed mainly by forsterite (Fo_80.6); diopside; enstatite (Fs_16.7); albite; troilite; Fe‐Ni metals such as iron and taenite; and some augite, chlorapatite, merrillite, chromite, and tetrataenite. Plagioclase‐like glass was also identified. Relative uniform chemical composition of basic silicates, partially brecciated textures, as well as skeletal taenite crystals into troilite veinlets suggest monomict breccia formed at conditions of rapid cooling. The Ko?ice meteorite is classified as ordinary chondrite of the H5 type which has been slightly weathered, and only short veinlets of Fe hydroxides are present. The textural relationships indicate an S3 degree of shock metamorphism and W0 weathering grade. Some fragments of the meteorite Ko?ice are formed by monomict breccia of the petrological type H5. On the basis of REE content, we suggest the Ko?ice chondrite is probably from the same parent body as H5 chondrite Morávka from Czech Republic. Electron‐microprobe analysis (EMPA) with focused and defocused electron beam, whole‐rock analysis (WRA), inductively coupled plasma mass and optical emission spectroscopy (ICP MS, ICP OES), and calibration‐free laser induced breakdown spectroscopy (CF‐LIBS) were used to characterize the Ko?ice fragments. The results provide further evidence that whole‐rock analysis gives the most accurate analyses, but this method is completely destructive. Two other proposed methods are partially destructive (EMPA) or nondestructive (CF‐LIBS), but only major and minor elements can be evaluated due to the significantly lower sample consumption.     

On the parameterization of biological influences on offshore sand wave dynamics

The bed of the North Sea is covered by sand waves and houses a great number of macrobenthic animals. These bio-engineers are known to have a significant influence on the stability of the bed and thereby on the geomorphology of the seabed. This paper proposes a parameterization of these bio-geomorphological interactions. Given the abundance of three dominant bio-engineers on the Dutch Continental Shelf, the predicted occurrence of sand waves, in which the parameterization is included, shows significantly better results, compared to the prediction for the default case without biology. Therefore, the inclusion of biological activity could be important to predict the occurrence of sand waves.     

Effects of meteoroid shape on cosmogenic nuclide production processes

The shape of meteorites is one of the major factors influencing the production of cosmogenic nuclides. Numerical simulations using the Los Alamos Code System (LCS) particle production and transport codes were done to investigate particle fluxes and production rates of cosmogenic nuclides ¹⁰Be, ²⁶Al, and ⁶⁰Co in meteoroids of spherical, ellipsoidal, and cylindrical shapes. The calculations show that fluxes of nuclear active particles and also production rates of cosmogenic nuclides are sensitive to the shape of the irradiated parent body.