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Accurate forecasting of river flows is one of the most important applications in hydrology, especially for the management of reservoir systems. To capture the seasonal variations in river flow statistics, this paper develops a robust modeling approach to identify and to estimate periodic autoregressive (PAR) model in the presence of additive outliers. Since the least squares estimators are not robust in the presence of outliers, we suggest a robust estimation based on residual autocovariances. A genetic algorithm with Bayes information criterion is used to identify the optimal PAR model. The method is applied to average monthly and quarter-monthly flow data (1959–2010) for the Garonne river in the southwest of France. Results show that the accuracy of forecasts is improved in the robust model with respect to the unrobust model for the quarter-monthly flows. By reducing the number of parameters to be estimated, the principle of parsimony favors the choice of the robust approach.  相似文献   
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The geomagnetic field components are periodically measured at repeat stations. The main objective of the repeat stations is to provide data for tracing the secular variation of the geomagnetic field components. Secular variation at the repeat station is generally different from that at geomagnetic observatory used in the data reduction. The effect of the secular variation differences on geomagnetic data reduction was estimated for the regions of Europe, North America (below 60°N) and Australia, respectively, during the period of 2000-2010. These estimations were obtained by using the monthly mean values of north, east and vertical components of geomagnetic field, recorded at geomagnetic observatories. The effects were calculated by using observatories pairs, with distances from 350 km (in Europe) to 3100 km (in North America and Australia). The maximal effects were found to be the smallest in east component in Europe and North America, and vertical component in Australia; the effects increase with time from a central reduction epoch and they are not constant during mentioned eleven years; they were less than 1 nT only in Europe, for distances between the observatories up to 1000 km in all three components and for periods spanning ±1 month from a central epoch. It was found that their year to year variability is mostly due to the non-eliminated external field residuals in the observatories monthly means; their effect is up to 3 nT for ±3 months from a central epoch. Further, the real effects were compared to those modeled by IGRF-12 model. The maximal differences between the real and the modeled values are below 4.5 nT in all three components, for ±3 months from a central epoch.  相似文献   
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More than ten years ago, the Geophysical Institute initiated the installation of a geomagnetic observatory in Croatia. Over the past decade, extensive surveys and studies have been conducted in order to determine the proper location for the observatory. Finally, in 2012, the observatory was established in Lonjsko Polje. This paper presents the first data recorded in the period 2012.5-2015.0. Also presented are the technical aspects and data processing techniques of this remotely operated observatory. Analysis of data quality and comparison with data from the surrounding INTERMAGNET observatories is discussed in detail. Although remote observatories cannot provide the ideal environment for magnetometers, the obtained results accentuate the potential of the new observatory to provide high-quality data. The establishment of this observatory paves the way for scientific and professional development of geomagnetism in Croatia.  相似文献   
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The aim of this work was to derive an accurate regional model of geomagnetic components on the Adriatic. Data of north, east and vertical geomagnetic components at repeat stations and ground survey sites enclosing the Adriatic Sea were used to obtain a geomagnetic model at 2010.5 epoch. The core field was estimated by use of the global Enhanced Magnetic Model, while the crustal field by a mathematical technique for expanding vector systems on a sphere into basis functions, known as spherical elementary current systems method. The results of this method were presented and compared to the crustal field estimations by the Enhanced Magnetic Model. The maps of isolines of the regional model are also presented.  相似文献   
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Fluid inclusions in mineralized graphite-sillimanite-mica schist from the Rampura-Agucha Pb-Zn-(Ag) deposit, Rajasthan, northwest India, have been investigated by microthermometry and Raman microspectrometry. Three different main types of fluid inclusions in quartz can be distinguished: (1) gaseous (CO2, partially mixed with CH4-N2), (2) low salinity aqueous inclusions (0–8 eq. wt% NaCl) and (3) high salinity aqueous inclusions (NaCl ± MgCl2-CaCl2). Low density CO2-rich and low salinity H2O inclusions are contemporaneous and occur, together with CH4-N2 inclusions, in close association with sulfide mineral inclusions. This indicates immiscibility between the gaseous and aqueous phase and participation of these fluids during the deposition or remobilization of the ore, which occurred over a wide P (1220 to 200 bar) and T (450 to 250 °C). Raman spectra of graphite indicate upper greenschist-facies metamorphic conditions, although host rocks have been metamorphosed at upper amphibolite-facies metamorphic conditions. This indicates that graphite re-equilibrated with the CO2-rich phase during retrograde metamorphism.  相似文献   
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