Post‐processing of medium‐range probabilistic hydrological forecasting: impact of forcing,initial conditions and model errors

The impact of errors in the forcing, errors in the model structure and parameters, and errors in the initial conditions is investigated in a simple hydrological ensemble prediction system. The hydrological model is based on an input nonlinearity connected with a linear transfer function and forced by precipitation forecasts from the European Centre for Medium‐Range Weather Forecast (ECMWF) Ensemble Prediction System (EPS). The post‐processing of the precipitation and/or the streamflow using information from the reforecasts performed by ECMWF is tested. For this purpose, hydrological reforecasts are obtained by forcing the hydrological model with the precipitation from the reforecast data. In the present case study, it is found that the post‐processing of the hydrological ensembles with a statistical model fitted on the hydrological reforecasts improves the verification scores better than the use of post‐processed precipitation ensembles. In the case of large biases in the precipitation, combining the post‐processing of both precipitation and streamflow allows for further improvements. During the winter, errors in the initial conditions have a larger impact on the scores than errors in the model structure as designed in the experiments. Errors in the parameter values are largely corrected with the post‐processing. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of satellite remote sensing to observe and analyse temporal changes of cocoa plantation in Ondo State,Nigeria

GeoJournal - This study examined the changes in the area of land occupied by cocoa plantation in Ondo state in order to provide useful information for effective agricultural policy to increase...     

The silicon isotopic composition of surface waters in the Atlantic and Indian sectors of the Southern Ocean

We report here the silicon isotopic composition (δ³⁰Si) of dissolved silicon (DSi) from 42 surface water samples from the Drake Passage, the Weddell Gyre, other areas south of the Southern Boundary of the Antarctic Circumpolar Current (ACC), and the ACC near the Kerguelen Plateau, taken between the beginning of February and the end of March 2007. From the beginning to end of the cruise (ANTXXIII/9), DSi diminished in the Antarctic by 50 μmol L⁻¹ while concentrations of nitrate + nitrite and phosphate showed no net decline, indicating that the high seasonal Si/N removal ratios well known for the Southern Ocean may be more related to the strength of the silicate pump in the Southern Ocean than to the instantaneous Si/N uptake ratio of diatoms. The δ³⁰Si of DSi in samples containing more than 20 μM DSi were strongly negatively correlated to DSi concentrations, supporting the use of δ³⁰Si as a proxy for DSi removal. The “open system” fractionation observed, ε = −1.2 ± 0.11‰, agrees well with results from previous work in other areas, and the estimate of the initial δ³⁰Si of DSi of +1.4‰ is not far off observations of the δ³⁰Si of DSi in Winter Water (WW) in this area. Results were used to model DSi draw down in the past from the δ³⁰Si of sediment cores, although isotopic fractionation during silica dissolution appeared to influence the δ³⁰Si of some surface water samples, inviting further study of this phenomenon.     

Turbiditic levee deposition in response to climate changes: The Var Sedimentary Ridge (Ligurian Sea)

The Var turbiditic system located in the Ligurian Sea (SE France) is an intermediate mud/sand-rich system. The particularity of the Var deep-sea fan is its single channel with abrupt bends and its asymmetric and hyper-developed levee on the right hand side: the Var Sedimentary Ridge. Long-term sediment accumulation on the Var Sedimentary Ridge makes this an ideal target for studying the link between onshore climate change and deep-sea turbidite stratigraphy. This paper focuses on the establishment of the first detailed stratigraphy of the levee, which is used to analyze the timing of overbank deposition throughout the last deglaciation. Main results indicate that high variability in turbidite frequencies and deposition rates along the Var Sedimentary Ridge are determined by two main parameters: 1) the progressive decrease of the levee height controlling the ability of turbidity currents to spill out from the channel onto the levee, and 2) climatic variations affecting the drainage basin, in particular changes in glacial condition since late Last Glacial Maximum to early Holocene. Compared to other deep-water areas, this study confirms the ability of turbiditic systems to record past climatic events on millennial timescales, and underlines the influence of European deglaciation on the observed decrease in turbidite activity in the Var canyon. The presence of a very narrow continental shelf and a single, large channel-levee system makes the Var Sedimentary Ridge a unique example of climate-controlled turbiditic accumulations.     

Extensional tectonics in Mt Parnon (Peloponnesus,Greece)

Peloponnesus in the south-western part of the Aegean is formed by a heterogeneous pile of alpine thrust sheets that was reworked by normal faulting from Upper Miocene to recent times. Upper Miocene–Lower Pliocene extension in Mt Parnon was accommodated by several mappable brittle detachment faults that exhibit a top-to-the-NE-ENE sense of shear. The hanging wall of the detachments comprises a number of highly tilted fault blocks containing abundant evidence of intense internal deformation by normal faulting and layer-parallel shearing contemporaneous with faulting. These fault blocks are remnants of a cohesive extensional block that slipped to the NE-ENE and broke up along high-angle normal faults that sole into or are cut by the detachments. The largest part of this block is located at the eastern edge of the metamorphic core forming the hanging wall of East Parnon high-angle normal fault that excised part of the aforementioned detachments. The lowermost metamorphic Unit of the nappe-pile does not seem to be affected by the previous extensional episode. Upper plate reconstruction shows that various units of the nappe-pile were affected by high-angle normal faults that linked to detachment faults in the weaker layers. Since the Middle-Upper Pliocene further exhumation of the metamorphic rocks has resulted in the formation of high-angle normal faults overprinting Neogene extensional structures and cut the entire nappe-pile. This new fault system tilted the earlier extensional structures and produced a NE-SW coaxial deformation of Mt Parnon.     

Stakeholder perspectives on use, trade, and conservation of medicinal plants in the Rasuwa district of central Nepal

People’s livelihood in several Himalayan regions largely depends on collection, use, and trade of medicinal plants. Traditional use is generally not a problem, but commercial gathering of selected species to meet increasing national and international demand can result in over-exploitation. Sustainable management of medicinal plants requires a clear understanding of the respective roles, responsibilities and viewpoints of the various stakeholders involved. Through personal interviews and group discussions, this study aimed at investigating the views of two stakeholder groups on use, trade and conservation of medicinal plants in the Rasuwa district of Nepal. Local people and district and national organizations agreed that medicinal plants are collected for a combination of commercial and personal uses. Perceptions on market availability differed significantly: 100 % of the respondents from district and national organizations saw markets as easily available, against only 36 % for local people. This could explain why medicinal plants were perceived by local people to contribute less to income generation than to livelihood improvement. Different viewpoints were also expressed concerning the status of medicinal plants in the district: 81 % of the respondents from district and national organizations considered that medicinal plants were threatened, compared to only 28 % for local people. Despite this disparity, both stakeholder groups agreed upon potential threats to medicinal plants: over-harvesting; habitat loss due to land-use change and deforestation; and over-grazing by livestock. Several challenges were identified regarding sustainable management of medicinal plants, such as ambiguous policies; lack of resources, information and infrastructures; habitat degradation; and over-exploitation. Despite these challenges, respondents agreed that the medicinal plants sector offers huge opportunities in the Rasuwa district, given resource availability, community awareness and motivation, and the priority given to the sector by governments and other agencies. Proper collaboration, communication and coordination among stakeholders are needed to grab these opportunities.     

Induced seismicity due to hydraulic fracturing near Blackpool,UK: source modeling and event detection

Journal of Seismology - Monitoring small magnitude induced seismicity requires a dense network of seismic stations and high-quality recordings in order to precisely determine events’...     

Trojans’ Odyssey: Unveiling the early history of the Solar System

In our present understanding of the Solar System, small bodies (asteroids, Jupiter Trojans, comets and TNOs) are the most direct remnants of the original building blocks that formed the planets. Jupiter Trojan and Hilda asteroids are small primitive bodies located beyond the ‘snow line’, around respectively the L₄ and L₅ Lagrange points of Jupiter at ～5.2?AU (Trojans) and in the 2:3 mean-motion resonance with Jupiter near 3.9?AU (Hildas). They are at the crux of several outstanding and still conflicting issues regarding the formation and evolution of the Solar System. They hold the potential to unlock the answers to fundamental questions about planetary migration, the late heavy bombardment, the formation of the Jovian system, the origin and evolution of trans-neptunian objects, and the delivery of water and organics to the inner planets. The proposed Trojans’ Odyssey mission is envisioned as a reconnaissance, multiple flyby mission aimed at visiting several objects, typically five Trojans and one Hilda. It will attempt exploring both large and small objects and sampling those with any known differences in photometric properties. The orbital strategy consists in a direct trajectory to one of the Trojan swarms. By carefully choosing the aphelion of the orbit (typically 5.3?AU), the trajectory will offer a long arc in the swarm thus maximizing the number of flybys. Initial gravity assists from Venus and Earth will help reducing the cruise time as well as the ΔV needed for injection thus offering enough capacity to navigate among Trojans. This solution further opens the unique possibility to flyby a Hilda asteroid when leaving the Trojan swarm. During the cruise phase, a Main Belt Asteroid could be targeted if requiring a modest ΔV. The specific science objectives of the mission will be best achieved with a payload that will perform high-resolution panchromatic and multispectral imaging, thermal-infrared imaging/ radiometry, near- and mid-infrared spectroscopy, and radio science/mass determination. The total mass of the payload amounts to 50?kg (including margins). The spacecraft is in the class of Mars-Express or a down-scaled version of Jupiter Ganymede Orbiter. It will have a dry mass of 1200?kg, a total mass at launch of 3070?kg and a ΔV capability of 700?m/s (after having reached the first Trojan) and can be launched by a Soyuz rocket. The mission operations concept (ground segment) and science operations are typical of a planetary mission as successfully implemented by ESA during, for instance, the recent flybys of Main Belt asteroids Steins and Lutetia.