Calibration and validation of rockfall modelling at regional scale: application along a roadway in Mallorca (Spain) and organization of its management   总被引：1，自引：0，他引：1  

Rosa María Mateos  Inmaculada García-Moreno  Paola Reichenbach  Gerardo Herrera  Roberto Sarro  Joan Rius  Raúl Aguiló  Federica Fiorucci 《Landslides》2016,13(4):751-763

The Tramuntana range, in the northwestern sector of the island of Mallorca (Balearic Islands, Spain), is frequently affected by rockfalls which have caused significant damage, mainly along the road network. In this work, we present the procedure we have applied to calibrate and validate rockfall modelling in this region, using 103 cases of the available detailed rockfall inventory (630 rockfall events collected since the eighteenth century). We have exploited STONE (Guzzetti et al. 2002), a GIS-based rockfall simulation software which computes 2D and 3D rockfall trajectories starting from a DTM and maps of the dynamic rolling friction coefficient and of the normal and tangential energy restitution coefficients. The appropriate identification of these parameters determines the accuracy of the simulation. To calibrate them, we have selected 40 rockfalls along the range which include a wide variety of outcropping lithologies. Coefficients values have been changed in numerous attempts in order to select those where the extent and shape of the simulation matched the field mapping. Best results were summarized with the average statistical values for each parameter and for each geotechnical unit, determining that mode values represent more precisely the data. Initially, for the validation stage, 10 well-known rockfalls exploited in the calibration phase have been selected. Confidence tests have been applied to their modelling results taking into account not only the success but also the mistakes. The best accuracy is obtained when the rockfall has a preferential trajectory and worse results when the rockfall follows two or more trajectories. Additionally, the greater the rockfall runout length, the less precise the simulation is. We have further validated the calibrated parameters along the Ma-road (111 km), the main transportation corridor in the range, using 63 rockfall events that occurred during the past 18 years along the road. Of the rockfalls where source areas were properly identified, 81.5 % are well represented by STONE modelling, as the travel paths and the depositional areas are successfully ascertained. Results of the analysis have been used by the Road Maintenance Service of Mallorca to assess hazard and risk posed by rockfall at regional scale to design the road management plan.  相似文献   

Erratum to: Impact of the arc length on GNSS analysis results     

Simon Lutz  Michael Meindl  Peter Steigenberger  Gerhard Beutler  Krzysztof Sośnica  Stefan Schaer  Rolf Dach  Daniel Arnold  Daniela Thaller  Adrian Jäggi 《Journal of Geodesy》2016,90(5):501-501

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Model for the Processing and Estimation of Dual Frequency Echo Sounder Observations in Detailed Bathymetries   总被引：1，自引：0，他引：1  

Raúl Pereda García  Felipe Piña García  Julio Manuel De Luis Ruiz  Raúl Husillos Rodríguez 《Marine Geodesy》2016,39(3-4):305-320

The dataset acquired by an echo sounder generally comprises outliers and erroneous measurements which must be automatically processed. The main aim of this research is the development and validation of an algorithm which permits detecting outliers, estimating their real value from data acquired with a multifrequency echo sounder, and verifying the measure according to the desired accuracy. The process considers the nature of the seabed and improves the density and number of lectures without globally compromising the precision, but enhancing it in areas with anomalous measurements. Twenty-nine percent of this type of measurements, which would have been otherwise rejected, have been estimated.  相似文献   

Application of an artificial neural network for a direct estimation of atmospheric instability from a next-generation imager     

Su Jeong Lee  Myoung-Hwan Ahn  Yeonjin Lee 《大气科学进展》2016,33(2):221-232

Atmospheric instability information derived from satellites plays an important role in short-term weather forecasting,especially the forecasting of severe convective storms. For the next generation of weather satellites for Korea's multi-purpose geostationary satellite program, a new imaging instrument has been developed. Although this imaging instrument is not designed to perform full sounding missions and its capability is limited, its multi-spectral infrared channels provide information on vertical sounding. To take full advantage of the observation data from the much improved spatiotemporal resolution of the imager, the feasibility of an artificial neural network approach for the derivation of the atmospheric instability is investigated.The multi-layer perceptron model with a feed-forward and back-propagation training algorithm shows quite a sensitive response to the selection of the training dataset and model architecture. Through an extensive performance test with a carefully selected training dataset of 7197 independent profiles, the model architectures are selected to be 12, 5000, and 0.3 for the number of hidden nodes, number of epochs, and learning rate, respectively. The selected model gives a mean absolute error,RMSE, and correlation coefficient of 330 J kg~(-1), 420 J kg~(-1), and 0.9, respectively. The feasibility is further demonstrated via application of the model to real observation data from a similar instrument that has comparable observation channels with the planned imager.  相似文献   

Future changes in drought characteristics over South Korea using multi regional climate models with the standardized precipitation index     

Yeon-Woo Choi  Joong-Bae Ahn  Myoung-Seok Suh  Dong-Hyun Cha  Dong-Kyou Lee  Song-You Hong  Seung-Ki Min  Seong-Chan Park  Hyun-Suk Kang 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):209-222

In this study, the projection of future drought conditions is estimated over South Korea based on the latest and most advanced sets of regional climate model simulations under the Representative Concentration Pathway (RCP4.5 and RCP8.5) scenarios, within the context of the national downscaling project of the Republic of Korea. The five Regional Climate Models (RCMs) are used to produce climate-change simulations around the Korean Peninsula and to estimate the uncertainty associated with these simulations. The horizontal resolution of each RCM is 12.5 km and model simulations are available for historical (1981-2010) and future (2021-2100) periods under forcing from the RCP4.5 and RCP8.5 scenarios. To assess the characteristics of drought on multiple time scales in the future, we use Standardized Precipitation Indices for 1-month (SPI- 1), 6-month (SPI-6) and 12-month (SPI-12). The number of drought months in the future is shown to be characterized by strong variability, with both increasing and decreasing trends among the scenarios. In particular, the number of drought months over South Korea is projected to increase (decrease) for the period 2041-2070 in the RCP8.5 (RCP4.5) scenario and increase (decrease) for the period 2071-2100 in the RCP4.5 (RCP8.5) scenario. In addition, the percentage area under any drought condition is overall projected to gradually decrease over South Korea during the entire future period, with the exception of SPI-1 in the RCP4.5 scenario. Particularly, the drought areas for SPI-1 in the RCP4.5 scenario show weakly positive long-term trend. Otherwise, future changes in drought areas for SPI-6 and SPI-12 have a marked downward trend under the two RCP scenarios.  相似文献   

Projections of high resolution climate changes for South Korea using multiple-regional climate models based on four RCP scenarios. Part 2: precipitation     

Seok-Geun Oh  Myoung-Seok Suh  Young-Suk Lee  Joong-Bae Ahn  Dong-Hyun Cha  Dong-Kyou Lee  Song-You Hong  Seung-Ki Min  Seong-Chan Park  Hyun-Suk Kang 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(2):171-189

Precipitation changes over South Korea were projected using five regional climate models (RCMs) with a horizontal resolution of 12.5 km for the mid and late 21st century (2026-2050, 2076- 2100) under four Representative Concentration Pathways (RCP) scenarios against present precipitation (1981-2005). The simulation data of the Hadley Centre Global Environmental Model version 2 coupled with the Atmosphere-Ocean (HadGEM2-AO) was used as boundary data of RCMs. In general, the RCMs well simulated the spatial and seasonal variations of present precipitation compared with observation and HadGEM2-AO. Equal Weighted Averaging without Bias Correction (EWA_NBC) significantly reduced the model biases to some extent, but systematic biases in results still remained. However, the Weighted Averaging based on Taylor’s skill score (WEA_Tay) showed a good statistical correction in terms of the spatial and seasonal variations, the magnitude of precipitation amount, and the probability density. In the mid-21st century, the spatial and interannual variabilities of precipitation over South Korea are projected to increase regardless of the RCP scenarios and seasons. However, the changes in area-averaged seasonal precipitation are not significant due to mixed changing patterns depending on locations. Whereas, in the late 21st century, the precipitation is projected to increase proportionally to the changes of net radiative forcing. Under RCP8.5, WEA_Tay projects the precipitation to be increased by about +19.1, +20.5, +33.3% for annual, summer and winter precipitation at 1-5% significance levels, respectively. In addition, the probability of strong precipitation (≥ 15 mm d^-1) is also projected to increase significantly, particularly in WEA_Tay under RCP8.5.  相似文献   

Which Dynamic Rupture Parameters Can Be Estimated from Strong Ground Motion and Geodetic Data?     

Sophie Peyrat  Kim B. Olsen  Raúl Madariaga 《Pure and Applied Geophysics》2004,161(11-12):2155-2169

— We have tested to which extent commonly used dynamic rupture parameters can be resolved for a realistic earthquake scenario from all available observations. For this purpose we have generated three dynamic models of the Landers earthquake using a single, vertical, planar fault with heterogeneity in either the initial stress, the yield stress, or the slip-weakening distance. Although the dynamic parameters for these models are inherently different, all the simulations are in agreement with strong motion, GPS, InSAR, and field data for the event. The rupture propagation and slip distributions obtained for each model are similar, showing that the solution of the dynamic problem is non-unique. In other words, it is not always possible to separate strength drop and the slip-weakening distance using rupture modeling, in agreement with the conclusions by GUATTERI and SPUDICH (2000).  相似文献   

Two adaptive algorithms for multipath time delay estimation   总被引：1，自引：0，他引：1  

Ching  P.C. So  H.C. 《Oceanic Engineering, IEEE Journal of》1994,19(3):458-463

The problem of time delay estimation (TDE) with multipath transmissions arises often in many sonar and radar systems. Two adaptive algorithms based on a parameter estimation approach are proposed to estimate the difference in arrival times of a signal at two separated sensors in the presence of multipath propagation. The first method uses an adaptive IIR filter to eliminate the multipath signal in each transmission channel prior to applying a constrained delay estimation algorithm to extract the time difference between the two received outputs. The second employs two constrained adaptive FIR filters to perform equalization of the multipath arrivals, and time delay is then derived using a constrained delay estimator similar to that in the first method. Computer simulations are presented to compare and contrast the tracing capability and convergence behavior of these multipath TDE methods  相似文献   

Analysis of a GPS Network Based on Functional Data Analysis     

Sonia Pérez-Plaza  Fernando Fernández-Palacín  Manuel Berrocoso  Raúl Páez  Belén Rosado 《Mathematical Geosciences》2018,50(6):659-677

This paper demonstrates the usefulness of approaching the dynamic study of the precise positioning of a network of permanent global positioning system (GPS) stations through functional data analysis. The displacement data for each GPS station, obtained from observations of the global navigation satellite system, are a discrete sample of the positioning curve. The aim of this paper is to reconstruct the original functions in order to use them as functional data. In the method presented in this paper, the geodetic series are obtained first by processing the GPS data with respect to a reference station. Second, for each station, a cleaning process is applied to eliminate the values considered as outliers, and the missing values are imputed by using a Kalman filter. Finally, the original functions are reconstructed by using smoothing techniques and by evaluating several bases of functions. Moreover, these functions are treated with statistical techniques for functional data. This procedure is applied to the permanent stations of the south of the Iberian peninsula and the north of Africa (SPINA) network. The topocentric series: east, north and up are analysed. In the analysis of the positioning curves, there is observed a synchronized behaviour of the functions in those periods of time with important seismic activity. This behaviour also appears in the analysis of the second principal component of the East and up dimensions. Furthermore, the first two principal components of the East coordinate enable us to make a classification of the stations in the SPINA network. The classification made is consistent with the previous knowledge of the tectonic plates in the studied area.  相似文献   

Validation of Galileo orbits using SLR with a focus on satellites launched into incorrect orbital planes     

Krzysztof Sośnica  Lars Prange  Kamil Kaźmierski  Grzegorz Bury  Mateusz Drożdżewski  Radosław Zajdel  Tomasz Hadas 《Journal of Geodesy》2018,92(2):131-148

The space segment of the European Global Navigation Satellite System (GNSS) Galileo consists of In-Orbit Validation (IOV) and Full Operational Capability (FOC) spacecraft. The first pair of FOC satellites was launched into an incorrect, highly eccentric orbital plane with a lower than nominal inclination angle. All Galileo satellites are equipped with satellite laser ranging (SLR) retroreflectors which allow, for example, for the assessment of the orbit quality or for the SLR–GNSS co-location in space. The number of SLR observations to Galileo satellites has been continuously increasing thanks to a series of intensive campaigns devoted to SLR tracking of GNSS satellites initiated by the International Laser Ranging Service. This paper assesses systematic effects and quality of Galileo orbits using SLR data with a main focus on Galileo satellites launched into incorrect orbits. We compare the SLR observations with respect to microwave-based Galileo orbits generated by the Center for Orbit Determination in Europe (CODE) in the framework of the International GNSS Service Multi-GNSS Experiment for the period 2014.0–2016.5. We analyze the SLR signature effect, which is characterized by the dependency of SLR residuals with respect to various incidence angles of laser beams for stations equipped with single-photon and multi-photon detectors. Surprisingly, the CODE orbit quality of satellites in the incorrect orbital planes is not worse than that of nominal FOC and IOV orbits. The RMS of SLR residuals is even lower by 5.0 and 1.5 mm for satellites in the incorrect orbital planes than for FOC and IOV satellites, respectively. The mean SLR offsets equal \(-44.9, -35.0\), and \(-22.4\) mm for IOV, FOC, and satellites in the incorrect orbital plane. Finally, we found that the empirical orbit models, which were originally designed for precise orbit determination of GNSS satellites in circular orbits, provide fully appropriate results also for highly eccentric orbits with variable linear and angular velocities.  相似文献