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41.
Paulescu Marius Badescu Viorel Budea Sanda Dumitrescu Alexandru 《Theoretical and Applied Climatology》2022,147(1-2):239-250
Theoretical and Applied Climatology - The Ångström–Prescott equation defines generically the relationship between solar energy available at ground level and sunshine duration. From... 相似文献
42.
Fluid mud dynamics in the Weser estuary turbidity zone tracked by high-resolution side-scan sonar and parametric sub-bottom profiler 总被引:1,自引:0,他引:1
Kerstin Schrottke Marius Becker Alexander Bartholomä Burghard W. Flemming Dierk Hebbeln 《Geo-Marine Letters》2006,26(3):185-198
Fluid mud in estuarine turbidity maximum zones (TMZ) can pose considerable navigation risks due to potentially substantial reductions in nautical depth, coupled with an inherent difficulty of detection by conventional echo-sounders. Despite intensive research efforts, however, our knowledge about the spatial and temporal dynamics of fluid mud is still not sufficient. In this study, the combined use of a side-scan sonar (Sportscan®, Imagenex) and a parametric sub-bottom profiler (SES-2000®, Innomar Technology GmbH) has proved successful for high-resolution fluid mud detection and volumetric quantification in an estuarine environment. In 2004 and 2005, repeated surveys were conducted in the navigation channel of the upper meso- to lower macrotidal Weser estuary TMZ (German North Sea coast) at different tidal stages and river discharges. Current velocity data were simultaneously collected by 1,200-kHz broadband ADCP (RDInstruments) measurements. Ground-truthing was carried out by means of grab sampling and gravity coring, adapted to fluid mud conditions. It was found that fluid mud occurrence in the Weser estuary is highly variable on time scales of a few hours and spatial scales of several metres. The riverbed is characterised by sand and mud deposits, and a complex morphology including subaqueous dunes and smooth bed deposits intermittently overlain by fluid mud. Thus, a continuous, coherent fluid mud body covering the entire TMZ riverbed was not observed. Rather, spatial distribution was patchy and highly dependent on suspended particulate matter (SPM) concentrations in the water column, as a result of which local fluid mud deposits varied in thickness from centimetres to metres. The formation of fluid mud was largely restricted to slack water, although slack-water conditions were not necessarily associated with large-scale fluid mud appearance. Advective SPM transport of resuspended fluid mud seems to be the most plausible explanation for the high spatial variability observed, even between two successive tides. The amount of fluid mud deposited and resuspended in the course of a tidal cycle can reach several 10s of tons even in small riverbed depressions. 相似文献
43.
Mean daily streamflow records from 44 river basins in Romania with an undisturbed runoff regime have been analyzed for trends with the nonparametric Mann‐Kendall test for two periods of study: 1961–2009 (25 stations) and 1975–2009 (44 stations). The statistical significance of trends was tested for each station on an annual and seasonal basis, for different streamflow quantiles. In order to account for the presence of serial correlation that might lead to an erroneous rejection of the null hypothesis, a trend‐free prewhitening was applied to the original data series. The regional field significance of trends is tested by a bootstrap procedure. Changes in the streamflow regime in Romania are demonstrated. The main identified trends are an increase in winter and autumn streamflow since 1961 and a decrease in summer flow since 1975. The streamflow trends are well explained by recent changes in temperature and precipitation that occurred in the last 50 years. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
44.
Kyungsoo Yoo Beth Weinman Simon Marius Mudd Martin Hurst Mikael Attal Kate Maher 《Applied Geochemistry》2011
How and how fast do hillslope soils form as the landscape’s morphology changes over time? Here results are shown from an ongoing study that simultaneously examines the morphologic and geochemical evolution of soil mantled hillslopes that have been exposed to distinctively different denudation history. In Northern Sierra Nevada, California, the authors are investigating a tributary basin to the Middle Fork Feather River. A major incision signal from the river is well marked in a knickpoint within the tributary basin which stretches from its mouth to the Feather River at an elevation of ~700 m to the plateau at an elevation of ~1500 m. Hillslopes are significantly steeper below the knickpoint. The area’s total denudation rates are currently being constrained using cosmogenic radio nuclides, but a previous study suggested an order of magnitude difference in total denudation rates below and above the knickpoint. When compared with topographic attributes calculated from LIDAR data, physical erosion rates can be modeled as a linear function of ridge top curvature. Surprisingly, over the wide range of total denudation rates, soil thicknesses do not vary significantly until a threshold point where soil mantled landscapes abruptly shift to bedrock dominated landscapes. Bioturbation by tree falls appear to buffer soil thickness over the wide range of physical soil erosion rates. From three hillslopes with different physical erosion rates, the concentrations of Zr, which were considered conserved during dissolution and leaching, were determined and used as a proxy for the degree of mass losses via chemical denudation. There is a general trend that colluvial soils along the hillslopes with lower physical erosion rates are enriched in fine size fractions, Zr, and pedogenic crystalline Fe oxides. Likewise, the saprolites show greater degrees of chemical denudation at the sites above the knickpoint, presumably because of the saprolites’ longer turnover time in the slowly eroding landscapes. In the two steep hillslopes below the knickpoint, no significant or systematic topgraphic trends were found for soil geochemistry. However, soils show increasing Zr enrichment in the downslope direction in the hillslope above the knickpoint, which suggests a critical denudation rate beyond which soils’ turnover time is too short to develop a geochemical catena. As detailed CRN-based soil production rates and catchment scale denudation rates are acquired, the data will be combined with a mass balance model to calculate the rates of chemical denudation and weathering in soils and saprolites along the denudation gradient. 相似文献
45.
Marie-Hélène Vandersmissen Anne-Marie Séguin Marius Thériault Christophe Claramunt 《Journal of Geographical Systems》2009,11(1):37-65
The research presented in this paper analyzes the emergent residential behaviors of individual actors in a context of profound
social changes in the work sphere. It incorporates a long-term view in the analysis of the relationships between social changes
in the work sphere and these behaviors. The general hypothesis is that social changes produce complex changes in the long-term
dynamics of residential location behavior. More precisely, the objective of this paper is to estimate the propensity for professional
workers to move house after a change of workplace. Our analysis draws on data from a biographical survey using a retrospective
questionnaire that enables a posteriori reconstitution of the familial, professional and residential lifelines of professional
workers since their departure from their parents’ home. The survey was conducted in 1996 in the Quebec City Metropolitan Area,
which, much like other Canadian cities, has experienced a substantial increase in “unstable” work, even for professionals.
The approach is based on event history analysis, a Temporal Geographic Information System and exploratory spatial analysis
of model’s residuals. Results indicate that 48.9% of respondents moved after a job change and that the most important factors
influencing the propensity to move house after a job change are home tenure (for lone adults as for couple) and number of
children (for couples only). We also found that moving is associated with changing neighborhood for owners while tenants or
co-tenants tend to stay in the same neighborhood. The probability of moving 1 year after a job change is 0.10 for lone adults
and couples while after 2 years, the household structure seems to have an impact: the probability increased to 0.23 for lone
adults and to 0.21 for couples. The outcome of this research contributes to furthering our understanding of a familial decision
(to move) following a professional event (change of job), controlling for household structure, familial, professional and
spatial contexts.
相似文献
Marius ThériaultEmail: |
46.
Fuzzy modelling of solar irradiation using air temperature data 总被引:1,自引:1,他引:0
Summary Fuzzy sets theory is applied to relate global solar irradiation to both the daily average and the daily amplitude of air temperature.
In addition to the presentation of a new mapping technique, from the input to the output of the model, an innovative approach
for the tuning of the fuzzy algorithm to fit a local meteo-climate is proposed. Since air temperature-based solar radiation
models are strongly dependent on the origin location, the adaptive method presented here is designed as a tool for potential
users to either increase the application area or to devise more precise local models. A critical assessment of fuzzy model
performances and limitations has been conducted. Results reported here demonstrate the potential of modelling solar irradiation
using fuzzy sets approach.
Authors’ address: E. Tulcan-Paulescu, M. Paulescu, Physics Department, West University of Timisoara, V. Parvan 4, 300223 Timisoara,
Romania. 相似文献
47.
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49.
Episodes of air pollution over Cape Town are identified using multi-year time series of SO2 and NOx concentrations. The associated meteorological conditions are studied both from synoptic and meso-scale perspectives using detailed observations, statistical analyses and numerical model simulations. Atmospheric conditions are most conducive to poor dispersion in the winter months, April to August. Episodes are initiated by the eastward passage of an intense, synoptic anticyclone over the Cape Town area. The 850 hPa geopotential height typically rises to 1600 gpm a day before the episode. Northeasterly berg winds are common and act to dry out the boundary layer. A nocturnal radiation inversion forms with a mean strength of 11 °C and extends from the surface to 953 hPa (500m). Gradient and thermal winds tend to cancel out providing for low net transport rates for near-surface emissions. Acoustic sounder profiles for two episodes illustrate a reduction of winds and turbulence within the boundary layer. The episode surface circulation is simulated using a two-layer model. Hills which lie upstream of Cape Town obstruct the northeasterly flow during the morning. 相似文献
50.