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101.
David Storz Hartmut Schulz Joanna J. Waniek Detlef E. Schulz-Bull Michal Kučera 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(1):107-124
Planktic foraminiferal (PF) flux and faunal composition from three sediment trap time series of 2002–2004 in the northeastern Atlantic show pronounced year-to-year variations despite similar sea surface temperature (SST). The averaged fauna of the in 2002/2003 is dominated by the species Globigerinita glutinata, whereas in 2003/2004 the averaged fauna is dominated by Globigerinoides ruber. We show that PF species respond primarily to productivity, triggered by the seasonal dynamics of vertical stratification of the upper water column. Multivariate statistical analysis reveals three distinct species groups, linked to bulk particle flux, to chlorophyll concentrations and to summer/fall oligotrophy with high SST and stratification. We speculate that the distinct nutrition strategies of strictly asymbiontic, facultatively symbiontic, and symbiontic species may play a key role in explaining their abundances and temporal succession. Advection of water masses within the Azores Current and species expatriation result in a highly diverse PF assemblage. The Azores Frontal Zone may have influenced the trap site in 2002, indicated by subsurface water cooling, by highest PF flux and high flux of the deep-dwelling species Globorotalia scitula. Similarity analyses with core top samples from the global ocean including 746 sites from the Atlantic suggest that the trap faunas have only poor analogs in the surface sediments. These differences have to be taken into account when estimating past oceanic properties from sediment PF data in the eastern subtropical North Atlantic. 相似文献
102.
Power-law spectra of 1–2 GHz narrowband dm-spikes 总被引：3，自引：0，他引：3
Twelve examples of clouds of narrowband dm-spikes, observed by the Ondejov radiospectrograph in the 1–2 GHz frequency range, are analyzed. After transforming of the frequency scales to heights in the solar atmosphere, the indices of the power-law power spectra are determined. The derived power-law indices are scattered in a broad range of values (–0.80––2.85). In some cases they considerably deviate from the previously found value of –5/3. A change of the power-law index above logk2.5 was also found in some cases. In the two longest events the time evolution of their power spectra as well as their indices were studied. While in most parts of the radio spectra the spectral index remains constant, in one part its absolute value increases with the spike intensity increase. Finally, the results, especially the broad range of power-law indices, are briefly discussed. 相似文献
103.
This paper examines the potential of the adaptive hp-FEM method for the numerical solution of time-dependent variably saturated Darcian flow problems described by the Richards equation. The method is illustrated on three model problems: a benchmark with known exact solution, groundwater seepage into a dry lysimeter box with time-dependent boundary conditions, and capillary barrier behavior under an intense infiltration. In the second part of the paper we present the weak formulation of the Richards equation for the Newton’s and Picard’s methods, give a brief overview of adaptive hp-FEM with emphasis on aspects that are usually not discussed in the literature, and we briefly introduce the open source adaptive hp-FEM library HERMES that was used to generate numerical results for this paper. All computations that we present are easily reproducible. 相似文献
104.
Žukovič Milan Borovský Michal Lach Matúš Hristopulos Dionissios T. 《Mathematical Geosciences》2020,52(1):123-143
Mathematical Geosciences - A novel Gibbs Markov random field for spatial data on Cartesian grids based on the modified planar rotator (MPR) model of statistical physics has been recently introduced... 相似文献
105.
本文讨论了无碰撞粒子系统中简并度对引力不稳定性的影响,计算了塌缩时间的Ｌａｎｄａｕ阻尼时间．在研究费密型暗物质占主导地位的宇宙中星系形成的理论时,系统分布函数的简并度对引力不稳定性的影响有重要意义． 相似文献
106.
107.
Tomáš Laburda Josef Krása David Zumr Jan Devátý Michal Vrána Nives Zambon Lisbeth Lolk Johannsen Andreas Klik Peter Strauss Tomáš Dostál 《地球表面变化过程与地形》2021,46(5):1067-1082
An understanding of splash erosion is the basis to describe the impact of rain characteristics on soil disturbance. In typical splash cup experiments, splashed soil is collected, filtered, and weighed. As a way to collect additional data, our experiments have been supplemented by a photogrammetric approach. A total of three soils were tested across three sites, one in the Czech Republic and two in Austria, all equipped with rain gauges and disdrometers to measure rainfall parameters. The structure from motion multiview stereo (SfM-MVS) photogrammetric method was used to measure the raindrops impact on the soil surface. The images were processed using Agisoft PhotoScan, resulting in orthophotos and digital elevation models (DEMs) with a resolution of 0.1 mm/pix. The surface statistics included the mean surface height (whose standard deviation was used as a measure of surface roughness), slope, and other parameters. These parameters were evaluated depending on soil texture and rainfall parameters. The results show a linear correlation between consolidation and splash erosion with a coefficient of determination (R2) of approximately 0.65 for all three soils. When comparing the change in soil volume with rainfall parameters, the best correlation was found with the maximum 30-minintensity (I30), resulting in R2 values of 0.48 (soil A, silt loam, 26% clay), 0.59 (soil B, silt loam, 18% clay), and 0.68 (soil C, loamy sand, 12% clay). The initial increase in the sample volume for the lowest splashed mass corresponds with the increase in the clay content of each of the soils. Soil A swells the most. Soil B swells less. Soil C does not swell at all and consolidates the most. We derived the relationship between the photogrammetrically measured change in surface height and the splash erosion (measured by weight) by accounting for the effect of the clay content. 相似文献
108.
109.
High accurate global navigation satellite systems (GNSS) require to correct a signal delay caused by the troposphere. The delay can be estimated along with other unknowns or introduced from external models. We assess the impact of the recently developed augmentation tropospheric model on real-time kinematic precise point positioning (PPP). The model is based on numerical weather forecast and thus reflects the actual state of weather conditions. Using the G-Nut/Geb software, we processed GNSS and meteorological data collected during the experiment using a hot-air balloon flying up to an altitude of 2000 m. We studied the impacts of random walk noise setting of zenith total delay (ZTD) on estimated parameters and the mutual correlations, the use of external tropospheric corrections, the use of data from a single or dual GNSS constellation and the use of Kalman filter and backward smoothing processing methods. We observed a significant negative correlation of the estimated rover height and ZTD which depends on constraining ZTD estimates. Such correlation caused a degraded performance of both parameters when estimated simultaneously, in particular for a single GNSS constellation. The impact of ZTD constraining reached up to 50-cm differences in the rover height. Introducing external tropospheric corrections improved the PPP solution regarding: (1) shortened convergence, (2) better overall robustness, particularly, in case of degraded satellite geometry, (3) less adjusted parameters with lower correlations. The numerical weather model-driven PPP resulted in 9–12- and 5–6-cm uncertainties in the rover altitude using the Kalman filter and the backward smoothing, respectively. Compared to standard PPP, it indicates better performance by a factor of 1–2 depending on the availability of GNSS constellations, the troposphere constraining and the processing strategy. 相似文献
110.