Improvement of Local Categorical Precipitation Forecasts from an NWP Model by Various Statistical Postprocessing Methods

Several statistical postprocessing methods are applied to results from a numerical weather prediction (NWP) model to test the potential for increasing the accuracy of its local precipitation forecasts. Categorical (Yes/No) forecasts for 12hr precipitation sums equalling or exceeding 0.1, 2.0 and 5.0 mm are selected for improvement. The two 12hr periods 0600-1800 UTC and 1800-0600 UTC are treated separately based on NWP model initial times 0000 UTC and 1200 UTC, respectively. Input data are taken from three successive summer seasons, April-September, 1994-96. The forecasts are prepared and verified for five synoptic stations, four located in the western Czech Republic, and one in Germany near the Czech-German border. Two approaches to statistical postprocessing are tested. The first uses Model Output Statistics (MOS) and the second modifies the MOS approach by applying a successive learning technique (SLT). For each approach several statistical models for the relationship between NWP model predictors and predictand were studied. An independent data set is used for forecast verification with the skill measured by a True Skill Score. The results of the statistical postprocessing are compared with the direct model precipitation forecasts from gridpoints nearest the stations, and they show that both postprocessing approaches provide substantially better forecasts than the direct NWP model output. The relative improvement increases with increasing precipitation amount and there is no significant difference in performance between the two 12hr periods. The skill of the SLT does not depend significantly on the size of the initial learning sample, but its results are nevertheless comparable with the results obtained from the MOS approach, which requires larger developmental samples.     

Historical and contemporary aspects of pluriactivity in the Curvature Sub–Carpathians of Romania

This paper focuses on the Curvature Sub–Carpathians, especially with respect to Buzau County. The region as a whole has always been relatively well-settled and agriculture has usually been combined with a range of local industrial and handicraft employments. A study of traditional domestic activities brings out a close connection between specific natural resources and characteristic features of traditional peasant household work. The Prahova Valley has been particularly favoured on account of the oil industry and a major transport axis connecting Bucharest with Brasov via Ploiesti, but elsewhere industry did not spread extensively beyond the county centres (Buzau, Focsani, Pitesti and Targoviste) and their immediate environs such as Colibasi and Doicesti. During the present transition phase the rural population is struggling to survive by combining elements of the modern and traditional economies. The main rural centres are relatively well off while the outlying villages are experiencing severe poverty problems. Apart from brandy distilling, traditional rural industries are no longer viable, although alternative systems of pluriactivity are under discussion. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sustained post-seismic effects on groundwater flow in fractured carbonate aquifers in Central Italy

A sustained increase in spring discharges was monitored after the 2016 Central Italy seismic sequence in the fractured carbonate aquifer of Valnerina–Sibillini Mts. The groundwater surplus recorded between August 2016 and November 2017 was determined to be between 400 and 500 × 10⁶ m³. In fractured aquifers, the post-seismic rise in spring discharges is generally attributed to an increase in bulk permeability caused by the fracture cleaning effect, which is induced by pore pressure propagation. In the studied aquifers, the large amount of additional discharge cannot only be attributed to the enhanced permeability, which was evaluated to be less than 20% after each main seismic event. A detailed analysis of the spring discharge hydrographs and of the water level at five gauging stations was carried out to determine the possible causes of this sudden increase in groundwater outflow. Taking into account the geological and structural framework, a conceptual model of a basin-in-series has been adopted to describe the complex hydrogeological setting, where the thrusts and extensional faults have clearly influenced the groundwater flow directions before and after the seismic sequence. The prevalent portion of the total post-seismic discharge surplus not explained by the increase in permeability has been attributed to changes in the hydraulic gradient that caused seismogenic fault rupture and the disruption in the upgradient sector of the aquifer. The additional flow calculated through the breach of the pre-existing hydrostructural barrier corresponds to approximately 470 × 10⁶ m³. This value is consistent with the total discharge increase measured in the whole study area, validating the proposed conceptual model. Consequently, a shift in the piezometric divide of the hydrogeological system has been induced, causing a potentially permanent change that lowers the discharge amount of the eastern springs.     

Numerical Investigation of a Methane Leakage from a Geothermal Well into a Shallow Aquifer

The potential environmental impacts on subsurface water resources induced by unconventional gas production are still under debate. Solving the controversy regarding the potential adverse effects of gas leakages on groundwater resources is therefore crucial. In this work, an interesting real-world case is presented in order to give further insight into methane multiphase and transport behavior in the shallow subsurface, often disregarded compared to the behavior in the deep subsurface. Multiphase flow and solute transport simulations were performed to assess the vulnerability of an existing shallow unconfined aquifer with respect to a hypothetical methane leakage resulting from a well integrity failure of a former deep geothermal well. The analysis showed that migration of gaseous methane through the aquifer under examination can be extremely fast (of the order of a few minutes), occurring predominantly vertically upwards, close to the well. By contrast, dissolved methane migration is largely affected by the groundwater flow field and occurs over larger time scales (of the order of months/years), covering a greater distance from the well. Overall, the real concern for this site in case of gas leakages is the risk of explosion in the close vicinity of the well. Predicted maximum gaseous fluxes (0.89 to 22.60 m³/d) are comparable to those reported for leaking wells, and maximum dissolved methane concentrations may overcome risk mitigation thresholds (7 to 10 mg/L) in a few years. Therefore, surface and subsurface monitoring before decommissioning is strongly advised to ensure the safety of the site.     

Testing polymineral post-IR IRSL and quartz SAR-OSL protocols on Middle to Late Pleistocene loess at Batajnica,Serbia

The loess–palaeosol sequence of Batajnica (Vojvodina region, Serbia) is considered as one of the most complete and thickest terrestrial palaeoclimate archives for the Middle and Late Pleistocene. In order to achieve a numerical chronology for this profile, four sets of ages were obtained on 18 individual samples. Equivalent doses were determined using the SAR protocol on fine (4–11 μm) and coarse (63–90 μm) quartz fractions, as well as on polymineral fine grains by using two elevated temperature infrared stimulation methods, pIRIR₂₉₀ and pIRIR₂₂₅. We show that the upper age limit of coarse quartz OSL and polymineral pIRIR₂₉₀ and pIRIR₂₂₅ techniques is restricted to the Last Glacial/Interglacial cycle due to the field saturation of the natural signals. Luminescence ages on coarse quartz, pIRIR₂₂₅ and pIRIR₂₉₀ polymineral fine grains are in general agreement. Fine quartz ages are systematically lower than the coarse quartz and pIRIR ages, the degree of underestimation increasing with age. Comparison between natural and laboratory dose response curves indicate the age range over which each protocol provides reliable ages. For fine and coarse quartz, the natural and laboratory dose response curves overlap up to ~150 and ~250 Gy, respectively, suggesting that the SAR protocol provides reliable ages up to c. 50 ka on fine quartz and c. 100 ka on coarse quartz. Using the pIRIR₂₂₅ and pIRIR₂₉₀ protocols, equivalent doses up to ~400 Gy can be determined, beyond which in the case of the former the natural dose response curve slightly overestimates the laboratory dose response curve. Our results suggest that the choice of the mineral and luminescence technique to be used for dating loess sediments should take into consideration the reported limited reliability.     

Earthquake loss assessment of precast RC industrial structures in Tuscany (Italy)

A seismic loss assessment for structural, non-structural, contents and business interruption is presented for precast reinforced concrete industrial buildings located in Italy. The correlation that exists between the performances of such spatially distributed buildings (i.e. spatial correlation) given a seismic event should be considered when estimating losses at a local or regional level. Loss assessment is thus performed herein using the OpenQuake-engine, an open-source tool capable of including the spatial correlation of ground-motion residuals and uncertainty in building vulnerability. The annual probability of structural collapse is employed as an initial risk measure, in which each industrial facility is considered as an individual asset. Then the economic loss for 300 buildings in the province of Arezzo is computed using a probabilistic event-based risk approach and presented in terms of annual average losses and losses at given annual rates of exceedance. The impact of the losses due to business interruption is also explored, and the extent of customer base is used as a prioritization metric for risk mitigation. It is observed that risk reduction should be applied as a priority in the facilities that are compromising the current level of acceptable risk, and the results show that business interruption has a significant contribution for economic losses, whose repercussions go beyond the regional level. Although this application is confined to the province of Arezzo, the same methodology can be used in other regions in Italy with similar building stock.     

Evaluation of nitrate levels in groundwater under agricultural fields in two pilot areas in central Chile: A hydrogeological and geochemical approach

The aim of this study is to evaluate the impact of the application of industrial fertilizers and liquid swine manure in groundwater in two pilot agricultural areas, San Pedro and Pichidegua, which have been under long‐term historic use of fertilizers. A comprehensive hydrogeological investigation was carried out to define the geology and the groundwater flow system. Chemical and isotopic tools were used to evaluate the distribution and behavior of the nitrate in the groundwater. The isotopic tools included δ¹⁸O, δ²H, and ³H, which provide information about the origin and residence time of the groundwater; δ¹⁵N‐NO₃^? and δ¹⁸O‐NO₃^?, which provide information about nitrate sources and processes that can affect nitrate along the groundwater flow system. The application rate of liquid manure and other fertilizers all together with land uses was also evaluated. The hydrogeological investigation identified the presence of a confined aquifer underneath a thick low‐permeability aquitard, whose extension covers most of the two study areas. The nitrate concentration data, excepting a few points in zones located near recharge areas in the upper part of the basins and lower areas at the valley outlets (San Pedro), showed nitrate concentration below 10 mgN/L at the regional scale. The isotope data for nitrate showed no influence of the liquid swine manure in the groundwater at the regional scale, except for the high part of the basins and the outlet of the San Pedro valley, which are areas fertilized by manure. This data showed that the regional aquifer on both pilot study areas is protected by the thick low‐permeability aquitard, which is playing an important role on nitrate attenuation. Evidence of denitrification was also found on both shallow and deep groundwater in the Pichidegua site. This study showed that a comprehensive hydrogeological characterization complemented by chemical and isotope data is key for understanding nitrate distribution and concentration in aquifers from areas with intensive agriculture activities.     

Laboratory measurements of super-resolving Toraldo pupils for radio astronomical applications

The concept of super-resolution refers to various methods for improving the angular resolution of an optical imaging system beyond the classical diffraction limit. Although several techniques to narrow the central lobe of the illumination Point Spread Function have been developed in optical microscopy, most of these methods cannot be implemented on astronomical telescopes. A possible exception is represented by the variable transmittance filters, also known as “Toraldo Pupils” (TPs) since they were introduced for the first time by G. Toraldo di Francia in 1952 (Toraldo di Francia, Il Nuovo Cimento (Suppl.) 9, 426, 1952). In the microwave range, the first successful laboratory test of TPs was performed in 2003 (Mugnai et al. Phys. Lett. A 311, 77–81, 2003). These first results suggested that TPs could represent a viable approach to achieve super-resolution in Radio Astronomy. We have therefore started a project devoted to a more exhaustive analysis of TPs, in order to assess their potential usefulness to achieve super-resolution on a radio telescope, as well as to determine their drawbacks. In the present work we report on the results of extensive microwave measurements, using TPs with different geometrical shapes, which confirm the correctness of the first experiments in 2003. We have also extended the original investigation to carry out full-wave electromagnetic numerical simulations and also to perform planar scanning of the near-field and transform the results into the far-field.     

IGS Tide Gauge Benchmark Monitoring Pilot Project (TIGA): scientific benefits

The establishment of a long-term stable global reference frame is important for studying sea level records for, e.g., climate-related studies. GPS stations connected to the tide gauge benchmarks provide the necessary technique. However, the analysis of existing GPS solutions showed inconsistencies within the time series especially for the height component. To solve related issues, in 2001 the IGS Tide Gauge Benchmark Monitoring Pilot Project was established. The aim is the processing and re-processing of GPS data of stations at or near tide gauges in order to provide homogeneous and high-quality estimates of the vertical motion. A second objective is the establishment, maintenance and expansion of existing network of GPS stations at tide gauges. During the recent years six different analysis centers have processed overlapping GPS at tide gauge networks and are providing individual solutions allowing now to provide a combined solution. The ansatz for the combination is explained and quality measures are given. In addition, on the basis of the reconstruction of sea level anomalies, the benefit of using the combined TIGA solution is demonstrated.     

Benthic mucilaginous aggregates in the Mediterranean Sea: Origin, chemical composition and polysaccharide characterization

Benthic mucilaginous aggregates are frequently formed in various parts of the Mediterranean basin, as in the Tyrrhenian and Adriatic Seas. Notwithstanding their wide spatial distribution, the role played by these aggregates in the biogeochemical cycling of organic matter is still largely unknown.The characteristics of the benthic aggregates examined in the present study showed that they are different from other mucilaginous aggregates, such as the “pelagic” ones that can form in the same areas in the water column and subsequently sediment to the seafloor. The aggregates are usually formed of structures of the filamentous macroalgae Acinetospora crinita, Chrysonephos lewisii and Nematochrysopsis marina. The elemental composition of the aggregates showed a marine macrophyte origin on the basis of the bulk organic matter content of the aggregates. Carbohydrates and proteins account for 26.6 to 55.9% of the organic carbon in the mucilage, respectively. Monosaccharide composition of exopolysaccharides in the mucilage aggregates revealed a characteristic pattern, with galactose, xylose or mannose and fucose as the major components. The relatively high content of deoxysugars is another distinctive feature. The abundant sulphate and uronic groups present in the polysaccharides in addition to their macromolecular dimensions and elongation contribute to inter-chain aggregation. Electron microscopic observations suggest that the polysaccharide fraction is the main macromolecular component in the formation of the persistent gel network in the aggregates.