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71.
This study starts by investigating the impact of the configuration of the variable-resolution atmospheric grid on tropical cyclone (TC) activity. The French atmospheric general circulation model ARPEGE, the grid of which is rotated and stretched over the North Atlantic basin, was used with prescribed sea surface temperatures. The study clearly shows that changing the position of the stretching pole strongly modifies the representation of TC activity over the North Atlantic basin. A pole in the centre of the North Atlantic basin provides the best representation of the TC activity for this region. In a second part, the variable-resolution climate model ARPEGE is coupled with the European oceanic global climate model NEMO in order to study the impact of ocean–atmosphere coupling on TC activity over the North Atlantic basin. Two pre-industrial runs, a coupled simulation and a simulation forced by the sea surface temperatures from the coupled one, are compared. The results show that the coupled simulation is more active in the Caribbean Sea and the Gulf of Mexico while the forced simulation is more active over eastern Florida and the eastern Atlantic. The difference in the distribution of TC activity is certainly linked with the location of TC genesis. In the forced simulation, tropical cyclogenesis is closer to the west African coast than in the coupled simulation. Moreover, the difference in TC activity over the eastern Atlantic seems to be related to two different mechanisms: the difference in African easterly wave activity over the west of Africa and the cooling produced, in the coupled simulation, by African easterly waves over the eastern Atlantic. Finally, the last part studies the impact of changing the frequency of ocean–atmosphere coupling on Atlantic TC activity. Increasing the frequency of coupling decreases the density of TC activity over the North Atlantic basin. However, it does not modify the spatial distribution of the TC activity. TC rainfalls are decreased by 8?% in the high frequency coupled run. 相似文献
72.
Delphine Yeghicheyan Dominique Aubert Martine Bouhnik‐Le Coz Jrme Chmeleff Sophie Delpoux Irina Djouraev Guy Granier Franois Lacan Jean‐Luc Piro Tristan Rousseau Christophe Cloquet Aurlie Marquet Christophe Menniti Catherine Pradoux Rmi Freydier Emmanoel Vieira da Silva‐Filho Krzysztof Suchorski 《Geostandards and Geoanalytical Research》2019,43(3):475-496
The natural river water reference material SLRS‐6 (NRC‐CNRC) is the newest batch of a quality control material routinely used in many international environmental laboratories. This work presents a nine‐laboratory compilation of measurements of major and trace element concentrations and their related uncertainties, unavailable in the NRC‐CNRC certificate (B, Cs, Li, Ga, Ge, Hf, Nb, P, Rb, Rh, Re, S, Sc, Se, Si, Sn, Th, Ti, Tl, W, Y, Y, Zr and REEs). Measurements were mostly made using inductively coupled plasma‐mass spectrometry. The results are compared with equivalent data for the last batch of the material, SLRS‐5, measured simultaneously with SLRS‐6 in this study. In general, very low concentrations, close to the quantification limits, were found in the new batch. The Sr isotopic ratio is also reported. 相似文献
73.
Jacques Dentzer Sophie Violette Simon Lopez Dominique Bruel 《Hydrogeology Journal》2017,25(7):1951-1965
This study is the first quantification of the combined impact of diffusive and advective paleoclimatic phenomena to explain the weak vertical thermal flux anomaly in the upper part of the Anglo-Paris intracratonic sedimentary basin in northern France. The aim of the research is to understand the mechanisms at the origin of the thermal flux anomaly at the level of the Meso-Cenozoic sediment pile. Based on a temperature profile representative of the basin, transient thermo-hydraulic simulations were performed along a representative vertical cross-section of about 400 km within the Lower Cretaceous multi-layer aquifer. Four paleoclimatic scenarios are the combination of two paleotemperature climatic forcings and two hydrodynamic regimes, one of them taking into account the interruption of the recharge linked to permafrost development. The simulation results clearly show the transient nature of the basin’s thermal regime. Then, for the reference well, the majority of the thermal flux anomaly can be explained by advective and paleoclimatic mechanisms with a decrease in geothermal flux simulated up to a little over 30 mW/m2, depending on the scenarios. Decrease in heat flux because of basin-scale subsurface flows in the Lower Cretaceous is around 15 mW/m2. There are several ways forward from this first simple model, including simulation of development of permafrost and also the integration of vertical flows in the basin by use of a three-dimensional model to better explain the data. 相似文献
74.
Harriet G. Orr Gavin L. Simpson Sophie des Clers Glenn Watts Mike Hughes Jamie Hannaford Michael J. Dunbar Cédric L. R. Laizé Rob L. Wilby Richard W. Battarbee Rob Evans 《水文研究》2015,29(5):752-766
Changes in water temperature can have important consequences for aquatic ecosystems, with some species being sensitive even to small shifts in temperature during some or all of their life cycle. While many studies report increasing regional and global air temperatures, evidence of changes in river water temperature has, thus far, been site specific and often from sites heavily influenced by human activities that themselves could lead to warming. Here we present a tiered assessment of changing river water temperature covering England and Wales with data from 2773 locations. We use novel statistical approaches to detect trends in irregularly sampled spot measurements taken between 1990 and 2006. During this 17‐year period, on average, mean water temperature increased by 0.03 °C per year (±0.002 °C), and positive changes in water temperature were observed at 2385 (86%) sites. Examination of catchments where there has been limited human influence on hydrological response shows that changes in river flow have had little influence on these water temperature trends. In the absence of other systematic influences on water temperature, it is inferred that anthropogenically driven climate change is driving some of this trend in water temperature. © 2014 The Authors. Hydrological Processes published by John Wiley & Sons Ltd. 相似文献
75.
76.
Peatlands are important carbon stores, but when drained (e.g. for agriculture), this carbon is released to the atmosphere as carbon dioxide (CO2, a greenhouse gas). Globally, at least 15% of peatlands have been drained, mostly in Europe and South‐east Asia, and are responsible for 5% of human‐derived CO2 emissions. Peatlands have been exploited for generations, but not without local to global consequences, particularly in South‐East Asia. However, recognition of the continuous environmental toll caused by peatland exploitation is leading to a need to change attitudes and practices, in order to propel a move towards a more balanced and responsible use of peat in both northern and tropical peatlands. 相似文献
77.
The flow structure on a gentle slope at Vallon dOl in the northern suburbs of Marseille in southern France has been documented by means of surface wind and temperature measurements collected from 7 June to 14 July 2001 during the ESCOMPTE experiment. The analysis of the time series reveals temperature and wind speed oscillations during several nights (about 60--90 min oscillation period) and several days (about 120–180 min oscillation period) during the whole observing period. Oscillating katabatic winds have been reported in the literature from theoretical, experimental and numerical studies. In the present study, the dynamics of the observed oscillating katabatic winds are in good agreement with the theory.In contrast to katabatic winds, no daytime observations of oscillating anabatic upslope flows have ever been published to our knowledge, probably because of temperature inversion break-up that inhibits upslope winds. The present paper shows that cold air advection by a sea breeze generates a mesoscale horizontal temperature gradient, and hence baroclinicity in the atmosphere, which then allows low-frequency oscillations, similar to a katabatic flow. An expression for the oscillation period is derived that accounts for the contribution of the sea-breeze induced mesoscale horizontal temperature gradient. The theoretical prediction of the oscillation period is compared to the measurements, and good agreement is found. The statistical analysis of the wind flow at Vallon dOl shows a dominant north-easterly to easterly flow pattern for nighttime oscillations and a dominant south-westerly flow pattern for daytime oscillations. These results are consistent with published numerical simulation results that show that the air drains off the mountain along the maximum slope direction, which in the studied case is oriented south-west to north-east. 相似文献
78.
Aristide Yemmafouo Chrétien Ngouanet Romeo Keumo Songong Nicodème Djikeng Teufack Sophie Ariane Djuidje 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2017,117(2):105-116
AbstractThis study examines how migrant households relocate their homes in two Cameroonian cities over the course of lifetimes or even generations. The central claim is that homeownership is the ultimate sign of integration into city life. Using qualitative and quantitative research methods (218 interviews, 30 focus groups and a household survey, sample size 686), the study argues that three key factors explain why people move: the quality of housing they can affords, the proximity to a workplace and the potential for homeownership. Three residential model trajectories are identified. The first describes a journey from being a new migrant who is a guest of family or friends in the city centre to being a married family with kids owning a home in the urban periphery. The second model continues that journey by returning back to the city centre in pursuit of more convenient, high-status home location (if finances permit). A third model describes moves to sites all over the city later in life as older individuals seek to maximize family income in the way they use multiple properties. Understanding residential mobility patterns has the potential to lead to a better public policies and more effective private investments in the housing sector. 相似文献
79.
Bruno Castelle Julien Bourget Nathalie Molnar Darrell Strauss Sophie Deschamps Rodger Tomlinson 《Coastal Engineering》2007
Currumbin Creek on the Australian Gold Coast is a wave-dominated tidal inlet which exhibits a particularly active morphology. The recent history of Currumbin Creek entrance has seen rapid growth of the entrance for access to the ocean by fishermen, as a world class surfing site, and as a recreational area. Before the construction of two groynes in the 70's, Currumbin Creek entrance was highly variable in terms of inlet location and sand bar characteristics due to a cyclical behaviour of spit migration. Nowadays, the entrance is stabilised. However, natural processes continue with the entrance infilling causing flood and navigation issues, resulting in a regular dredging program to maintain an open entrance and for regular beach nourishment plans. 相似文献
80.
Abstract Lytechinus variegatus and Arbacia punctulata have been studied primarily in inshore, shallow‐water areas. However, they are abundant in deeper waters on the Florida gulf‐coast shelf and seem important components of the benthic communities there. Lytechinus variegatus occurs alone on sand bottoms and A. punctulata occurs alone on rubble bottoms in these deeper waters. The species also co‐occur there on heterogeneous bottoms, each in a distinct microhabitat with A. punctulata on rubble and L. variegatus on surrounding sand. Characteristics of the sea urchins in these different deeper‐water habitat types and at one nearshore site with a heterogeneous rubble‐sand bottom were compared. Over the 2‐year study, offshore individuals of both species had low gut and gonad indices and the maximum size of individuals did not change. This suggests food limitation and low production. Offshore, A. punctulata had a higher Aristotle's lantern index and lower gut and gonad indices in populations where it co‐occurred with L. variegatus compared to populations where it occurred alone. The Aristotle's lantern index of L. variegatus did not differ among the offshore sites. Neither species seemed food limited at the nearshore site. Although productivity is lower at the offshore sites, both species extend their distribution and reproduction potential by existing there. 相似文献