UBV photometry and spectroscopy of an anomalous SS Cygni outburst     

U. Hopp  C. Wolk 《Astrophysics and Space Science》1984,98(2):237-243

We presentUBV photometry and some spectroscopic observations of an anomalous SS Cyg outburst. A comparison of the photometric and spectroscopic properties of normal and anomalous outbursts gives evidence that the differences between them are caused by different behaviour of the Balmer discontinuity.  相似文献   

Organic lacustrine sediment varves as indicators of past precipitation changes: a 3,000-year climate record from Central Finland     

Saija Saarni  Timo Saarinen  Anssi Lensu 《Journal of Paleolimnology》2015,53(4):401-413

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Simulated effect of soil depth and bedrock topography on near‐surface hydrologic response and slope stability     

Cristiano Lanni  Jeff McDonnell  Luisa Hopp  Riccardo Rigon 《地球表面变化过程与地形》2013,38(2):146-159

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Local seismic network for monitoring of a potential nuclear power plant area     

Timo Tiira  Marja Uski  Jari Kortström  Outi Kaisko  Annakaisa Korja 《Journal of Seismology》2016,20(2):397-417

This study presents a plan for seismic monitoring of a region around a potential nuclear power plant. Seismic monitoring is needed to evaluate seismic risk. The International Atomic Energy Agency has set guidelines on seismic hazard evaluation and monitoring of such areas. According to these guidelines, we have made a plan for a local network of seismic stations to collect data for seismic source characterization and seismotectonic interpretations, as well as to monitor seismic activity and natural hazards. The detection and location capability of the network were simulated using different station configurations by computing spatial azimuthal coverages and detection threshold magnitudes. Background noise conditions around Pyhäjoki were analyzed by comparing data from different stations. The annual number of microearthquakes that should be detected with a dense local network centered around Pyhäjoki was estimated. The network should be dense enough to fulfill the requirements of azimuthal coverage better than 180° and automatic event location capability down to ML?～?0 within a distance of 25 km from the site. A network of 10 stations should be enough to reach these goals. With this setup, the detection threshold magnitudes are estimated to be ML?=??0.1 and ML?=?0.1 within a radius of 25 and 50 km from Pyhäjoki, respectively. The annual number of earthquakes detected by the network is estimated to be 2 (ML?≥?～ ?0.1) within 25 km radius and 5 (ML?≥?～?0.1 to ～0.1) within 50 km radius. The location accuracy within 25 km radius is estimated to be 1–2 and 4 km for horizontal coordinates and depth, respectively. Thus, the network is dense enough to map out capable faults with horizontal accuracy of 1–2 km within 25 km radius of the site. The estimation is based on the location accuracies of five existing networks in northern Europe. Local factors, such as seismic noise sources, geology and infrastructure might limit the station configuration and detection and location capability of the network.  相似文献   

利用后向散射特性从高分辨率SAR影像中提取建筑物高度     

刘康  Timo Balz  廖明生 《武汉大学学报(信息科学版)》2012,37(7):806-809

研究了一种基于雷达后向散射特性,从单张星载高分辨率SAR影像提取建筑物高度的方法。该方法通过检测建筑物二次散射强度,同时获取目标方位角、入射角等参数以及相关介质特性等信息,根据后向散射几何光学模型估算建筑物高度。实验验证了对于相当一部分典型建筑物都能够获得较为理想的高程估计值,进而证明了该方法提取建筑物高度的可行性和有效性。  相似文献   

Pollution history from 256 BC to AD 2005 inferred from the accumulation of elements in a varve record of Lake Korttajärvi in Finland     

Jarmo J. Meriläinen  Virve Kustula  Allan Witick  Eeva Haltia-Hovi  Timo Saarinen 《Journal of Paleolimnology》2010,44(2):531-545

In order to assess the importance of different pollution sources for the increase in element concentration and accumulation, historical changes in selected elements were studied in the annually laminated sediment of Lake Korttajärvi in Central Finland (62°20′N; 25°41′E). The sediment chronology based on varve counting (256 BC to AD 2005) provided a unique opportunity to explore and date signals of metal emissions, including the ancient metallurgical activities of the Roman Empire at the beginning of the Current Era. Records of this kind are mostly lacking in Finland and northernmost Europe. The stratigraphic sequence of element concentrations did not reflect any major changes in the lake, but changes in element accumulation rates provided distinct pollution signals caused by airborne fallout, catchment erosion, and to some extent municipal wastewater loading. The maximum bulk sedimentation recorded in the twentieth century was 11-fold and organic sedimentation 4-fold higher than the mean background sedimentation rate (256 BC to AD 1019). The increase in the accumulation rates of the majority of the elements, such as Cd, Sn, Pb, Si, Ni, B, Cu, Zn, Sr, Na, K, Sb, Ca, Cr, U and Mg, in descending order, was at least equal to that of bulk sedimentation or much greater, especially for Cd, Sn, and Pb. Changes in the accumulation of Co, Fe, Mn, Mo and As were small and mainly followed those of organic sedimentation. The earliest pollution signals were those of Pb recorded in AD 1055–1141. A weak signal of Pb pollution from the Roman Era was detected in metal concentrations, but this could not be confirmed by the accumulation rate data for Pb.  相似文献   

Autoregressive filtering versus linear detrending in estimation of fluxes by the eddy covariance method   总被引：10，自引：7，他引：3  

Üllar Rannik  Timo Vesala 《Boundary-Layer Meteorology》1999,91(2):259-280

The application of autoregressive running mean filtering (RMF) and linear detrending (LDT) in the estimation of turbulent fluxes by the eddy covariance method is analysed. The systematic, as well as the random, errors of the fluxes arising from filtering and/or limited observation time effects are described. To observe negligible systematic errors in fluxes, the RMF has to be applied with moderately long time constants. However, the obtained flux values are subject to increased random errors during periods of non-stationarity and the method leads to systematic overestimation of variances. These shortcomings are not inherent in the LDT approach, which is recommended for use. But the systematic errors of fluxes due to LDT are not negligible under certain experimental conditions and have to be accounted for. The corrections are important because the relatively small errors in short-period fluxes can translate to significant errors in long-period averages. The corrections depend on the turbulence time scales, which should be preferably estimated as ensemble mean variables for a particular site.  相似文献   

Locating regional seismic events with global optimization based on interval arithmetic   总被引：4，自引：0，他引：4  

Matti Tarvainen  Timo Tiira  & Eystein S. Husebye 《Geophysical Journal International》1999,138(3):879-885

More than 1000 seismic events in northern Europe at distances of up to 400  km from the detecting network are located using an optimization method in which the global minimum of the traveltime function residuals is searched for using an Interval Arithmetic (IA) method. Epicentres are determined using P waves detected by the Finnish national seismic network: up to 15 stations were used in the analysis. The IA results coincide with locations provided by the University of Helsinki bulletins with a median location bias of 7.6  km.
  A second data set of 59 explosions in the Siilinjärvi mine in central Finland was examined in detail, because the locations of the explosions were known exactly. In this case, the median difference of IA locations was 3.8  km from the average location of mine explosions, while all 59 events were located within 9  km of the 'true' epicentres. The corresponding median error of the University of Helsinki locations was smaller (3.2  km), but some Helsinki locations were well over 10  km from the mine. The convergence towards the global optimum using interval arithmetic was fast when compared with the conventional least-squares approaches for epicentre determinations.  相似文献   

The relevance of preferential flow in catchment scale simulations: Calibrating a 3D dual-permeability model using DREAM     

Luisa Hopp  Barbara Glaser  Julian Klaus  Thilo Schramm 《水文研究》2020,34(5):1237-1254

The occurrence of preferential flow in the subsurface has often been shown in field experiments. However, preferential flow is rarely included in models simulating the hydrological response at the catchment scale. If it is considered, preferential flow parameters are typically determined at the plot scale and then transferred to larger-scale simulations. Here, we successfully used the optimization algorithm DiffeRential Evolution Adaptive Metropolis (DREAM) to calibrate a 3D physics-based dual-permeability model directly at the catchment scale. In order to keep computational costs of the optimization routine at a reasonable level, we limited the number of parameters to be calibrated to the ones that had been shown before to be most influential for the simulation of discharge. We also calibrated parameters of the matrix domain and the macropore domain with a fixed parameter ratio between soil layers instead of calibrating every layer separately. These ratios reflected observed depth profiles of soil hydraulic properties at our study site. The dual-permeability parameter sets identified during calibration were able to simulate observed discharge time series satisfactorily but did not outperform a calibrated single-domain reference model scenario. Saturated hydraulic conductivities of the macropore domain were calibrated such that they became very similar to matrix saturated hydraulic conductivities, thereby effectively removing the effect of macropores. This suggests that the incorporation of vertical preferential flow as represented by the dual-permeability approach was not relevant for reproducing the hydrometric response reasonably well in the studied catchment. We also tested the scale-invariance of the calibrated dual-permeability parameter sets by using the parameter sets performing best at catchment scale to simulate plot-scale bromide depth profiles obtained from tracer irrigation experiments. This parameter transfer proved to be not successful, indicating that soil hydraulic parameters are scale-variant, independent of the direction of parameter transfer.  相似文献   

Distribution of nitrate over sea-salt and soil derived particles — Implications from a field study   总被引：1，自引：0，他引：1  

Tuomo A. Pakkanen  Veli-Matti Kerminen  Risto E. Hillamo  Minna Màkinen  Timo Màkelà  Aki Virkkula 《Journal of Atmospheric Chemistry》1996,24(2):189-205

A method for determining the distribution of supermicrometer nitrate between size-segregated sea-salt and soil derived particles is presented. The analysis is based on field data from six measurements at a coastal site in southern Finland, and on a theoretical treatment taking into account the transfer of gaseous species onto particle surfaces and their subsequent reaction. Significant amounts of nitrate were found in both the particle types, with the fraction of nitrate associated with soil particles varying from 20–50% in the 1–2 m size to near 90% in particles larger than 10 m. Overall, the nitrate accumulation followed closely the relative abundances of these two particle types. Two overlapping modes in supermicron nitrate mass size distributions could be identified. The lower mode, associated with sea-salt, was located between the surface-area and volume distribution of sodium peaking at about 2–3 m of EAD. The upper mode peaked at 3–5 m and followed more closely the surface-area distribution of calcium in all samples. At our site, the accumulation of nitrate into both particle types was shown to be limited by an effective surface reaction rate rather than by gas-phase diffusion. This rate was estimated to be considerably larger for sea-salt particles. Strong evidence in support of the saturation of nitrate in sea-salt particles were obtained.  相似文献