Exploratory and Instantaneous Swimming Speeds of Amphidromous Fish School in Shallow-Water Coastal Lagoon Channels

Fish school swimming speeds is essential for ecological and management studies. The multibeam sonar in horizontal beaming provided dynamic echo traces of mobile fish schools. We used two school swimming speed indicators: the average of a series of instantaneous speed values, and the exploratory speed. These swimming speeds were estimated for each fish school observed on the basis of their Euclidian position within the sonar beams. The average ISS values per school ranged from 0.15 m s⁻¹ to 4.46 m s⁻¹, while the ESS values per school were lower, ranging from 0.04 m s⁻¹ to 3.77 m s⁻¹. Multibeam sonar technology makes it possible to measure fish school swimming speeds in their natural habitat at small spatio-temporal scales. This methodology can therefore be used to analyse in situ their movements, and has a wide range of applications in behavioural studies and management purposes.     

The 2011 expedition to the El'gygytgyn impact structure,Northeast Russia: Toward a new geological map for the crater area

El'gygytgyn is a 3.6 Ma, 18 km diameter, impact crater formed in an approximately 88 Ma old volcanic target in Northeast Siberia. The structure has been the subject of a recent ICDP drilling project. In parallel to those efforts, a Russian‐German expedition was undertaken in summer 2011 to investigate the permafrost soil, lake terraces, and the volcanic rocks of the southern and eastern crater rim. This provided the unique opportunity for mapping and sampling of the volcanic target rocks around a large part of this complex impact structure. Samples from 43 outcrops were collected and analyzed petrographically and geochemically. The results were combined with earlier mapping outcomes to create a new geological map of this impact structure and its immediate environs, at the scale of 1:50,000. Compositions of our rock suites are compared with the lithologies of the 2009 ICDP drill core. The ignimbrite described as lower bedrock in the ICDP drill core shows petrographically and chemically strong similarities to the rhyolitic and rhyodacitic ignimbrites observed on surface. The suevite sequence exposed in the ICDP drill core is a mixture of all observed target rocks at their respective proportions in the area. In contrast to previous studies, the calculated average target composition of El'gygytgyn takes the contribution of the basic target rocks into consideration: mafic and intermediate rocks approximately 7.5%, and felsic rocks approximately 92.5%.     

Climate change policy responses for Canada's Inuit population: The importance of and opportunities for adaptation

We identify and examine how policy intervention can help Canada's Inuit population adapt to climate change. The policy responses are based on an understanding of the determinants of vulnerability identified in research conducted with 15 Inuit communities. A consistent approach was used in each case study where vulnerability is conceptualized as a function of exposure-sensitivity to climatic risks and adaptive capacity to deal with those risks. This conceptualization focuses on the biophysical and human determinants of vulnerability and how they are influenced by processes and conditions operating at multiple spatial-temporal scales. Case studies involved close collaboration with community members and policy makers to identify conditions to which each community is currently vulnerable, characterize the factors that shape vulnerability and how they have changed over time, identify opportunities for adaptation policy, and examine how adaptation can be mainstreamed. Fieldwork, conducted between 2006 and 2009, included 443 semi-structured interviews, 20 focus groups/community workshops, and 65 interviews with policy makers at local, regional, and national levels. Synthesizing findings consistent across the case studies we document significant vulnerabilities, a function of socio-economic stresses and change, continuing and pervasive inequality, and magnitude of climate change. Nevertheless, adaptations are available, feasible, and Inuit have considerable adaptive capacity. Realizing this adaptive capacity and overcoming adaptation barriers requires policy intervention to: (i) support the teaching and transmission of environmental knowledge and land skills, (ii) enhance and review emergency management capability, (iii) ensure the flexibility of resource management regimes, (iv) provide economic support to facilitate adaptation for groups with limited household income, (v) increase research effort to identify short and long term risk factors and adaptive response options, (vi) protect key infrastructure, and (vii) promote awareness of climate change impacts and adaptation among policy makers.     

Dynamics of the turbidity maximum zone in a macrotidal estuary (the Gironde,France): Observations from field and MODIS satellite data

Over a 1-year period, field and satellite measurements of surface water turbidity were combined in order to study the dynamics of the turbidity maximum zone (TM) in a macrotidal estuary (the Gironde, France). Four fixed platforms equipped with turbidity sensors calibrated to give the suspended particulate matter (SPM) concentration provided continuous information in the upper estuary. Full resolution data recorded by the moderate resolution imaging spectroradiometer (MODIS) sensors onboard the Terra and Aqua satellite platforms provided information in the central and lower estuary twice a day (depending on cloud cover). Field data were used to validate a recently developed SPM quantification algorithm applied to the MODIS ‘surface reflectance’ product. The algorithm is based on a relationship between the SPM concentration and a reflectance ratio of MODIS bands 2 (near-infrared) and 1 (red). Based on 62 and 75 match-ups identified in 2005 with MODIS Terra and Aqua data, the relative uncertainty of the algorithm applied to these sensors was found to be 22 and 18%, respectively.Field measurements showed the tidal variations of turbidity in the upper estuary, while monthly-averaged MODIS satellite data complemented by field data allowed observing the monthly movements of the TM in the whole estuary. The trapping of fine sediments occurred in the upper estuary during the period of low river flow. This resulted in the formation of a highly concentrated TM during a 4-month period. With increasing river flow, the TM moved rapidly to the central estuary. A part of the TM detached, moved progressively in the lower estuary and was finally either massively exported to the ocean during peak floods or temporary trapped (settled) on intertidal mudflats. The massive export to the ocean was apparently the result of combined favorable environmental conditions: presence of fluid mud near the mouth, high river flow, high tides and limited wind speeds. The mean SPM concentration within surface waters of the whole estuary showed strong seasonal variations but remained almost unchanged on a 1-year-basis. These observations suggest that the masses of suspended sediments exported toward the ocean and supplied by the rivers were almost equivalent during the year investigated (2005). Results show the usefulness of information extracted from combined field and current ocean color satellite data in order to monitor the transport of suspended particles in coastal and estuarine waters.     

Structures tectoniques et contraintes de cheminement des eaux dans les aquifères karstiques du barrois (Lorraine/Champagne,France)

Résumé

Entre Lorraine et Champagne, dans l’est du Bassin parisien, au contact des calcaires portlandiens du Barrois et des sables et argiles crétacés du Perthois, se développe un karst couvert. Le paysage de côtes est ici perturbé par une tectonique souple (synclinal de Treveray) et cassante (fossé d’effon-drement de la Marne) déterminant l’organisation spatiale des écoulements. En période d’étiage, les méthodes hydrologiques (profils hydrologiques lissés, traçages), permettent de montrer l’influence de cette tectonique d’ondulation et de basculement sur l’écoulement des rivières barroises (Saulx, Marne). Fractures et microfractures influencent la zone de transit vertical des eaux du karst (zone des puits) tandis que les failles compartimentent les aquifères (système du Rupt-du-Puits, 21 km de conduits, 13 km²). Les méthodes d’études hydrologiques, confirment le basculement de la région vers l’ouest déduit des comparaisons de nivellement. © Elsevier, Paris     

Spatial and Temporal Validation of In-Situ and Satellite Weather Data for the South West Agricultural Region of Australia

Seasonal variations in weather have significant impacts on crop yields. The accuracy of weather data is an import-ant consideration for crop yield models. This ...     

A Method for Monitoring the Heat Flux from an Urban District with a Single Infrared Remote Sensor

The proposed methodology relies on the modelling capabilities of the thermo-radiative model Solene to simulate the heat and radiation energy exchanges between an actual urban district and the atmosphere. It is based on the comparison of the simulated upward infrared and sensible heat flux diurnal cycles that may be measured by elevated sensors above the three-dimensional scene, as a function of sensor position: the heat flux is a function of an equivalent surface temperature given by the infrared sensor and an equivalent heat transfer coefficient deduced from Solene simulations with the actual geometry. The method is tested against measurements obtained in the city centre of Toulouse, France during an experimental campaign in 2004–2005. To improve the computation of the heat exchanges between air and building surfaces a new algorithm is first implemented, based on an empirical model of the wind distribution within street canyons. This improvement is assessed by a direct comparison of the simulated brightness surface temperatures of the Toulouse city centre to measurements obtained with an airborne infrared sensor. The optimization of the infrared remote sensor position is finally analyzed as a function of its height above the mean roof level: it allows evaluation of the heat flux from an urban district when the three different classes of surfaces (roofs, walls, grounds) have similar contributions to the infrared flux towards the sensor, and to the heat flux into the atmosphere.     

Rainfall–interception–evaporation–runoff relationships in a semi-arid catchment,northern Limpopo basin,Zimbabwe

Abstract

Two types of monthly water balance models at basin scale are used: PE models use precipitation and potential evapotranspiration (PET) as their observed input data, whereas P models need only precipitation. Calibration proceeds by comparing model runoff and observed runoff. Calibration is entirely automatic with the exclusion of subjective elements. All models differ only by their actual evapotranspiration equations. PE models from previous papers are generalized essentially by replacing the constant evapotranspiration parameter by a periodic one, thus increasing the number of parameters by two (a “parameter” is an unknown constant to be estimated, and which is a characteristic of the river basin to be described). P models use a periodic “driving force”, which is intended to represent periodicity of hydrological phenomena, normally originating in the (unavailable) PET time series. These eight PE models and three P models are then applied to 55 river basins in 10 countries with widely diverging climates and soil conditions. A marked improvement of model performance in about one third of the basins is due to the introduction of the above mentioned periodic functions. Even when PET data are available it is sometimes useful to consider P models. P models scarcely perform less well than PE models. An engineer, wanting to try out as few models as possible on a given river basin, can restrict his attention to the optimization of two or three models. The paper is an extension of a long effort towards monthly water balance models, and is believed to give a solution in most circumstances.     

Persistence of quartz disequilibrium in groundwater flows

This paper shows how constraints can be placed on the prediction of quartz equilibration distance in subsurface water flows. This is achieved here by coupling kinetic equations for the simple (SiO_2(quartz)-H₂O_(water)) system to various groundwater flow parameters (compaction flow, aquifer, convection flow, and hydrothermal system). This approach determines: (1) the order of magnitude of the downstream distance necessary for equilibrium to be attained, when a flowing solution is initially out of equilibrium; and (2) the minimum flow velocity required to sustain a sufficient quartz undersaturation or oversaturation over a given distance. Geological conditions under which specific water-rock interactions take place can be constrained with those calculations. Water flow in most subsurface environments, as idealized here, tends to equilibrate with the quartz-rich hosting medium on a very short distance (≤ 1 m). Major exceptions are: (1) the topmost part of a compacting pile, (2) shallow and fast-flowing aquifers, and (3) most hydrothermal systems.     

Micrometeorological Measurements in a Street Canyon during the Joint ATREUS-PICADA Experiment

In order to investigate the microclimatic conditions in a street canyon, a physical model was used to conduct the Joint ATREUS-PICADA Experiment (JAPEX) in situ experimental campaign. Four lines of buildings simulated by steel containers were installed to form three parallel street canyons at 1:5 scale, with width/height aspect ratio approximately 0.40. The reference wind and atmospheric conditions were measured, as well as the flow velocity and direction in the street. Preliminary results concern street canyon ventilation and thermal effects on in-canyon airflow, and show that vortical motions appear for reference wind directions perpendicular to the street axis. The presence of adjacent rows of buildings did not appear to significantly influence the flow character within the canyon for the case of a low aspect ratio corresponding to a skimming flow regime. The flow structure was not significantly affected by the thermal effects although some slight interference occurred in the lower part of the canyon. An analysis of horizontal temperature gradients indicated that a thin boundary layer develops near the heated facade. These facts imply that the thermal effects are considerable only very close to the wall.