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81.
Levels of spatial segregation in Western European cities are persistent over space and time. To demonstrate the degree or appearance of spatial segregation, most studies on urban residential patterns still rely on fixed spatial units, aspatial measures and single scales. However, a spatial or temporal comparison of patterns and levels of segregation based on such units or metrics is not without problems. To that end, this paper takes an explicit geographic approach and considers individualized neighborhoods using EquiPop-software, allowing various scales. Using the k-nearest neighbors for all individuals increases international comparability and facilitates interpretation, so far often hampered in segregation research. This multiscalar, multigroup comparative approach on ethnic urban geographies – using Belgium as a case study – provides an empirical illustration of a valuable method and tool applicable in segregation research, thereby furthering the comprehension of the increasingly diverse urban geographies and building on emerging work in the US, Europe and beyond. 相似文献
82.
Dan Hammarlund Ramon Aravena Lena Barnekow Bjørn Buchardt Göran Possnert 《Journal of Paleolimnology》1997,18(3):219-233
A 9000-year carbonate-rich sediment sequence from a small hard-water lake in northernmost Sweden was studied by means of multi-component stable carbon isotope analysis. Radiocarbon dating of different sediment fractions provides chronologic control and reveals a rather constant hard-water effect through time, suggesting that the lake has remained hydrologically open throughout the Holocene. Successive depletion of 13C in fine-grained calcite and carbonate shells during the early Holocene correlate with a change in catchment vegetation from pioneer herb communities to boreal forest. The vegetational change and associated soil development likely gave rise to an increased supply of 13C-depleted carbon dioxide in groundwater recharging the lake. This process is therefore believed to be the main cause of decreasing values of 13C in dissolved inorganic carbon of the lake and thereby in limnic carbonates. Strongly 13C-depleted sedimentary organic matter may be related to enhanced kinetic fractionation during photosynthetic assimilation by means of proton pumping in Characean algae. This interpretation is supported by a substantial offset between 13C of DIC as recorded by mollusc shells and 13C of fine-grained calcite. 相似文献
83.
84.
S. Casadio A. Di Sarra G. Fiocco D. Fuà F. Lena M. P. Rao 《Boundary-Layer Meteorology》1996,79(4):375-391
Convective plume patterns, characteristic of clear sky and light wind daytime boundary layers over land, were observed for two nights with a tri-axial Doppler sodar operated in the central area of Rome during the summer of 1994. An urban heat island effect, combined with a continuation of a breeze from the sea late into night during both days, is believed to be responsible for the observed nocturnal convection. Estimates of the surface heat flux and the vertical velocity scaling parameter are obtained from profiles of vertical velocity variance, and the Raman lidar water vapor measurements are used to obtain the humidity scaling parameter. Convective scaling results for vertical wind and humidity fairly agree with the results of other experiments and models. On the basis of available measurements, it appears that mixed-layer similarity formulations used to characterize the daytime convective boundary layer over horizontally homogeneous surfaces can also be applied to the nocturnal urban boundary layer during periods of reasonable convective activity. 相似文献
85.
Case Studies of the Wintertime Convective Boundary-Layer Structure in the Urban Area of Milan, Italy
The paper describes some aspects of the convective boundary-layer structure based on simultaneous sodar and tethersonde measurements during a field experiment in the urban area of Milan in the period 8 to 20 February, 1993. During this period, fog episodes and strong low-level elevated inversions (with lower boundaries < 400 m) were observed most of the time. A close agreement in the mixing height values, derived from the sodar and tethersonde profiles, has been achieved under these conditions. The validity of the similarity relationships, which have been originally derived to describe the vertical velocity variance and heat flux profiles over horizontally homogeneous terrain under quasi-stationary conditions, was evaluated when applied to the urban boundary layer. 相似文献
86.
Henny A.J. Van Lanen Gregor Laaha Daniel G. Kingston Tobias Gauster Monica Ionita Jean‐Philippe Vidal Radek Vlnas Lena M. Tallaksen Kerstin Stahl Jamie Hannaford Claire Delus Miriam Fendekova Luis Mediero Christel Prudhomme Ekaterina Rets Renata J. Romanowicz Sébastien Gailliez Wai Kwok Wong Mary‐Jeanne Adler Veit Blauhut Laurie Caillouet Silvia Chelcea Natalia Frolova Lukas Gudmundsson Martin Hanel Klaus Haslinger Maria Kireeva Marzena Osuch Eric Sauquet James H. Stagge Anne F. Van Loon 《水文研究》2016,30(17):3097-3104
87.
L. Vergni F. Todisco B. Di Lena F. Mannocchi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(7):1901-1915
In this paper a composite analysis was used to assess the influence of the North Atlantic Oscillation (NAO) on the winter daily rainfall and seasonal runoff at 28 stations of the Abruzzo region (Central Italy) during the period 1951–2012. Compositing was based on NAO? and NAO+ phases, identified by mean winter values of the normalized NAO index (NAOI) ≤?0.75 and ≥+0.75, respectively. In accordance with previous studies, it was found that NAO? phases determine, in general, a greater number of wet days (N w ) and (consequently) higher seasonal rainfall amounts in comparison to NAO+ phases. However, the NAO influence is characterized by a certain spatial variability, that can mostly be explained by orographic effects due to the Apennine Mountains. This is particularly evident for the mean rainfall depth per event (P e ) that, during NAO? phases, increases for the stations to the west of the Apennines, while it decreases for most of the stations to the east. The structure of winter daily rainfall of NAO+ and NAO? type, was described by a simple but effective first-order Markov process, determining the transition probabilities P01 (dry to wet) and P10 (wet to dry) and modelling the rainfall depth on wet days by a Weibull distribution. The most significant influence of NAO concerns P01 and the shape parameter of the Weibull distribution that are both higher during the NAO? phase. This means that NAO? phases are characterized by less persistent dry periods and less variable daily rainfall depths, in comparison to NAO+ phases. The effect of these differences on the winter seasonal runoff was explored by applying a Curve Number rainfall-runoff model. Significant increments of the mean seasonal runoff during NAO? phases were observed only for few stations (mainly on the west), characterized by corresponding increments of N w , P tot and P e .). NAO+ phases, instead, are characterized by relevant increments of the seasonal runoff variability, particularly on the eastern areas. In this context, the important regulating function of the watershed conditions was also discussed. 相似文献
88.
Lena Menzel Kai Horst GeorgePedro Martínez Arbizu 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(8):839-864
We examined the large-scale distribution of deep-sea harpacticoid copepods at the species level, in order to clarify the underlying processes of copepod dispersal. The study was based on samples collected from 12 regions and a total of 113 stations: 57 stations at depths between 1107 and 5655 m on abyssal plains in the South and North Atlantic, Southern Ocean, southern Indian Ocean, and the Pacific Ocean, and 56 stations above 900 m in the North Atlantic and eastern Mediterranean Sea.We chose the genus Mesocletodes Sars, 1909 as an ideal group to study the large-scale distribution of harpacticoid copepods in the deep oceans. Clear apomorphies and a comparatively large body size of about 1 mm allow rapid recognition of allied species in meiofauna samples. In addition, Mesocletodes represents more than 50% of the family Argestidae Por, 1986, one of the most abundant harpacticoid families in the deep sea.The geographical distributions of 793 adult females of Mesocletodes belonging to 61 species throughout the South and North Atlantic, Southern Ocean, southern Indian Ocean, Pacific Ocean, and eastern Mediterranean Sea indicated that most species are cosmopolitan. Neither the topography of the sea bottom nor long distances seem to prevent species from dispersing. Passive transport by bottom currents after resuspension is likely the propulsive factor for the dispersal of Harpacticoida, while plate tectonics and movement of individuals in the sediment may play relatively minor roles. 相似文献
89.
Irene Lena Hudson 《Climatic change》2010,100(1):143-171
The importance of global environmental questions has significantly advanced the impact of climate change phenology. Whilst
spatial applications continue to be a core application of phenology; in recent years the temporal dimension has also been
revisited, with studies showing that temporal changes, either with a natural or an anthropogenic origin, have significantly
altered phenological rhythms and seasonal development—changes attributed now to an anthropogenically induced temperature increase.
This paper explores and introduces recent and newly developing analytic methods in phenology; with a view to increasing an
interdisciplinary perspective and dialogue. Of particular focus is how we can and best deal with nonlinearity of phenological
change in time and with multiple location studies; rigorously model the inherent multivariate time series structures in climate-phenology
data; further Bayesian and non-Bayesian methods, detect multiple change-points; map seasonality calendars; model de-synchronisation
of species globally; invoke old fashioned, yet rarely used circular statistical methods; adapt new transitional state modelling
of phenophases with respect to climate and progress a unified paradigm for meta analytic studies in phenology. The provision
of uncertainty analysis is also still much needed in climate-related phenological research. Reaching consensus on design,
method of data collection and comparable analytic methods is integral to advancing the generalisability of phenological results;
as is a consensus on inclusion criterion for studies selected for phenological meta-analytic studies. A coherent nomenclature
is critically required, but it is currently lacking in many areas of phenology. 相似文献
90.