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1.
Summary The increasing use of weather radar quantitative precipitation estimates, particularly in automatic applications such as operational
hydrometeorological modelling or assimilation in numerical weather prediction (NWP) models, has promoted the development of
quality control procedures on radar data.
Anomalous propagation (AP) of the radar beam due to deviation from the standard refractivity vertical profile, is one of the
factors that may affect seriously the quality of radar observations because of the increase in quantity and intensity of non-precipitating
clutter echoes and consequent contamination of the estimated rainfall field. Another undesired effect of AP is the change
in the expected radar echo height, which may be relevant when correcting for beam blockage in radar rainfall estimation in
complex terrain. The aim of this paper is to study the use of NWP mesoscale forecasts to predict and monitor AP events.
A nested 15-km grid resolution version of the MASS model has been used to retrieve refractivity profiles in the coastal area
of Barcelona, near a weather radar and a radiosonde station. Using the refractivity profiles two different magnitudes were
computed: the vertical refractivity profile of the lowest 1000 m layer and a ducting index which describes the existence and
intensity of the most super-refractive layer contained in the lowest 3-km layer. A comparison between model forecasts and
radiosonde diagnostics during a six-month period showed that the model tended to underestimate the degree of super-refraction,
with a bias of 4 km−1 and RMSE of 11 km−1 in the 1-km vertical refractivity gradient. Further analysis of the data showed that a combination of previous observations
and forecasts allowed to produce modified forecasts improving the original direct model output, decreasing substantially the
bias, reducing the RMSE by 20% and improving the skill by 40%, beating also radiosonde observations persistence. 相似文献
2.
J. Bech M. Suarez F. Reverter P. Tume P. Sánchez N. Roca A. Lansac 《Journal of Geochemical Exploration》2010
Data of trace element composition of phosphorites are scarce and incomplete. Phosphorites of different origins can vary substantially in trace element contents. In this paper 20 trace element concentrations of 35 sample phosphorites are reported. The geographical provenance is: Bayovar-Sechura (Peru), Khouribga, Youssoufia and Boucraa (Morocco), Gafsa (Tunisia), Florida (USA), Idaho and Phosphoria Formation (USA), North Carolina (USA), Algeria, Israel, Senegal, Syria and Togo. Aqua regia extracts were used to estimate the “pseudototal” values, following standard procedures (ISO 11466, 2002) and measured by ICP-AES and ICP-MS. 相似文献
3.
C. Pérez-Sirvent M.J. Martínez-Sánchez M.L. García-Lorenzo J. Molina M.L. Tudela W. Mantilla J. Bech 《Journal of Geochemical Exploration》2010
The objective of this study was to determine the selenium content in soils from the Region of Murcia (SE, Spain) and to study the possible relationship between mineralogical composition, soil properties and selenium content. In addition, generic reference level (GRL) for selenium was determined according to Spanish legislation. For this study, 490 samples were selected in areas subjected to agricultural activity or abandoned agricultural soils with natural vegetation. Five different zones were established in order to study selenium variability. Four different mineralogical groups were established, based on significant relationship with the mineralogical composition, and each sample was included in one mineralogical group. The results showed that the concentration of selenium is correlated with the electrical conductivity, sulphate content and with the mineralogical composition, particularly positively with quartz and in a negative way with calcite percentage. In addition, selenium level was positively correlated with the phyllosilicate content. Established GRL for selenium varies with the mineralogical group, having a great transcendence from the legal and economic points of view. 相似文献
4.
Natural Hazards - High-resolution aerial imagery may provide very detailed information about strong-convective wind events, which can be very useful to enhance and make more robust severe weather... 相似文献
5.
Study of the total lightning activity in a hailstorm 总被引：1，自引：0，他引：1
Joan Montany Serge Soula Nicolau Pineda Oscar van der Velde Pere Clapers Glria Sol Joan Bech D. Romero 《Atmospheric Research》2009,91(2-4):430-437
A thunderstorm that developed over northeastern Spain on 16 June 2006 is analyzed. This severe thunderstorm produced hailstones as large as 40 mm and had a lifetime of 3 h and 30 min. Radar cross-sections show strong vertical development with cloud echo tops reaching an altitude of 13 km. The specific characteristics of the lightning activity of this storm were: (i) a large amount (81%) of negative cloud-to-ground (−CG) flashes with very low peak currents (< 10 kA in absolute value), (ii) a very large proportion of intra-cloud (IC) flashes with an IC/CG ratio reaching about 400, (iii) a large number of “short” IC flashes (with only 1-VHF source according to SAFIR detection), (iv) a large increase of the −CG flash rate and of the CG proportion near the end of the storm. The rate of −CG flashes with a low peak current were observed to evolve similarly to the rates of IC flashes. Most of them have been assumed to be IC flashes misclassified by the Spanish Lightning Detection Network (SLDN). They have been filtered as it is usually done for misclassified +CG flashes. After this filtering, CG flash rates remained very low (< 1 min− 1) with +CG flashes sometimes dominant. All the particular lightning activity characteristics similar to those observed in the Severe Thunderstorm Electrification and Precipitation Study (STEPS) campaigns support the hypothesis that this thunderstorm could have had an inverted-polarity or complex charge structure. The maximum IC flash rate (67 min− 1) peaked 24 min before the presence of reflectivity higher than 60 dBZ. The IC activity abruptly decreased during the period when reflectivity was dramatically increasing. The time of maximum reflectivity observed by radar was consistent with the times of reported hail at the ground. 相似文献
6.
Trine Agervig Carstensen Anton Stahl Olafsson Nynne Marie Bech Thea Schmidt Poulsen Chunli Zhao 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2015,115(2):142-156
Cycling plays an important role in low-carbon transitions. Around the globe, cities are constructing bicycle infrastructure. The city of Copenhagen has a bicycle-friendly infrastructure celebrated for its fine-meshed network. This study documents the spatio-temporal development of Copenhagen’s bicycle infrastructure and explores how the development corresponds to other processes of urban transformation. The study builds on historical maps of bicycle infrastructure that are digitised into geographical information, which allows for a comprehensive analysis of the formation of the network. In search for identifying drivers, the study analyses the city’s spatial growth pattern, migration pattern, development of road network and changes in the transport culture. Analyses reveal that the bicycle infrastructure expanded at a relatively constant pace during distinct periods of urban transformation, including periods when the city suffered from spatial, economic and demographic decline, and dominance of car traffic. By discussing reasons and demands for constructing bicycle infrastructure, the study identifies four distinct periods in which bicycle infrastructure was constructed to enhance comfort and safety (first cycling city); the flow for cars (car city); urban liveability for soft transport (liveable city); and, finally, to improve the flow for cyclists as part a strategic re-design of urban space (liveable cycling city). 相似文献
7.
Lydéric France Benoit Ildefonse Juergen Koepke Florent Bech 《Journal of Volcanology and Geothermal Research》2010,189(3-4):340-346
The oxygen fugacity and therefore the iron redox state of a melt is known to have a strong influence on the liquid line of descent of magmas and thus on the composition of the coexisting melts and crystals. We present a new method to estimate this critical parameter from electron probe microanalyses of two of the most common minerals of basaltic series, plagioclase and clinopyroxene. This method is not based on stoichiometric calculations, but on the different partitioning behaviour of Fe3+ and Fe2+ between both minerals and a melt phase: plagioclase can incorporate more Fe3+ than Fe2+, while clinopyroxene can incorporate more Fe2+ than Fe3+. For example, the effect of oxidizing a partly molten basaltic system (Fe3+ is stabilized with respect to Fe2+) results in an increase of FeOtotal in plagioclase, but a decrease in the associated clinopyroxene. We propose an equation, based on published partition coefficients, that allows estimating the redox state of a melt from these considerations. An application to a set of experimental and natural data attests the validity of the proposed model. The associated error can be calculated and is on average < 1 log unit of the prevailing oxygen fugacity.In order to reduce the number of different variables influencing the Fe2+/Fe3+ mineral/melt equilibrium, our model is restricted to basaltic series with SiO2 < 60% that have crystallized at intermediate to low pressure (< 0.5 GPa) and under relatively oxidizing conditions (?FMQ > 0; where FMQ is the fayalite–magnetite–quartz oxygen buffer equilibrium), but it may be parameterized for other conditions. A spreadsheet is provided to assist the use of equations, and to perform the error propagation analysis. 相似文献
8.
9.
Bech M 《Marine pollution bulletin》2002,44(9):887-896
The present investigation is the most extensive survey of imposex in gastropods from the west coast of Thailand. Imposex in Thais distinguenda increased significantly (p < 0.001; Chi Square test for trend) from 1996 to 2000 at 21 stations in Phangna Bay, Thailand. Females with imposex increased, extending from 3.5 km in 1996 to 10 km from the harbour areas in 1999 and 2000. Increasing intensity of imposex was also observed for Thais bitubercularis from 1996 to 2000. The less sensitive species: Morula musiva, Morula granulata, Morula margariticola and Thais rufotincta only developed imposex at the three main areas of intense shipping activities. T. bitubercularis and T. distinguenda are recommended as indicators of tributyltin (TBT) in Southeast Asia because of their sensitivity and wide distribution in the region. The results suggest that TBT contamination is worsening, against global trends, because regulations prohibiting the use of TBT-based paints, do not exist in Thailand. 相似文献
10.
Adolfo Vicente Magaldi Joan Bech Jerónimo Lorente 《Meteorology and Atmospheric Physics》2009,105(3-4):121-132
Weather radar quantitative precipitation estimates (QPE) are one of the usual tools to monitor rainfall intensity remotely by forecasters on duty or by automatic systems such as hydrological models. Derivation of radar QPE requires a set of robust quality control procedures to address a number of different factors. In particular, significant departures from the standard temperature and moisture atmospheric vertical profiles may increase dramatically the refraction of the radar beam. This anomalous propagation (AP or anaprop) of the microwave radar energy may therefore increase the number of spurious echoes due to ground clutter and contribute, with non-realistic rainfall, to the estimated precipitation field. Based on previous experience of geostationary satellite imagery usage to depict cloud-free areas in precipitation analysis systems, a methodology to incorporate Meteosat Second Generation (MSG) observations and NWP data in the quality control of weather radar QPE was implemented considering two different algorithms. They were validated with two different verification data sets, built with manually edited radar data and rain gauge observations using HKS, PC and FAR scores. The evaluation of the scores was performed for weak (<15 dBZ), stronger and all echoes and for day, night and day and night conditions. One of the methods dealing with weak echoes at night improved PC from 80 to 97% and decreased FAR from 0.32 to 0.19. The results obtained indicate that the technique shows potential for operational application complementing other existing methodologies designed to improve the quality of weather radar precipitation estimates. 相似文献