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191.
Effects of shear in the convective boundary layer: analysis of the turbulent kinetic energy budget 总被引:1,自引:0,他引:1
Effects of convective and mechanical turbulence at the entrainment zone are studied through the use of systematic Large-Eddy
Simulation (LES) experiments. Five LES experiments with different shear characteristics in the quasi-steady barotropic boundary
layer were conducted by increasing the value of the constant geostrophic wind by 5 m s-1 until the geostrophic wind was equal to 20 m s-1. The main result of this sensitivity analysis is that the convective boundary layer deepens with increasing wind speed due
to the enhancement of the entrainment heat flux by the presence of shear.
Regarding the evolution of the turbulence kinetic energy (TKE) budget for the studied cases, the following conclusions are
drawn: (i) dissipation increases with shear, (ii) the transport and pressure terms decrease with increasing shear and can
become a destruction term at the entrainment zone, and (iii) the time tendency of TKE remains small in all analyzed cases.
Convective and local scaling arguments are applied to parameterize the TKE budget terms. Depending on the physical properties
of each TKE budget contribution, two types of scaling parameters have been identified. For the processes influenced by mixed-layer
properties, boundary layer depth and convective velocity have been used as scaling variables. On the contrary, if the physical
processes are restricted to the entrainment zone, the inversion layer depth, the modulus of the horizontal velocity jump and
the momentum fluxes at the inversion appear to be the natural choices for scaling these processes. A good fit of the TKE budget
terms is obtained with the scaling, especially for shear contribution. 相似文献
192.
Time series modelling of landings in Northwest Mediterranean Sea 总被引:2,自引:0,他引:2
193.
Jordi Giménez Maria J. Borque Antonio J. Gil Pedro Alfaro Antonio Estévez Emma Suriñach 《Studia Geophysica et Geodaetica》2009,53(1):81-98
The seismic activity of the Guardamar-Torrevieja zone (Eastern Betic Cordillera, SE Spain) can be associated with the Bajo
Segura fault zone, an E-W reverse blind fault with secondary NW-SE dextral faults. A high-precision levelling profile 30 kilometers
long was set up and levelled in 1997 to monitor the vertical displacement of this active fault zone. This profile runs parallel
to an older high-precision levelling line included in the Spanish first order levelling network measured by the Instituto
Geográfico Nacional (IGN) in two different campaigns (1934 and 1976). The 1997 line was relevelled in 2003 and 10 new benchmarks
were set up, both to increase benchmark density and to restore some of the 1997 benchmarks that had been destroyed. We have
used the 1976 IGN and the 2003 measurement to construct a recent vertical movements profile with a significant time difference
(27 years). This recent vertical movements profile shows that the vertical movements are very small, nearly equal to the error
bars, with a 0.2 mm/year rise in the town of Guardamar, and a 0.2 mm/year subsidence of the southern part of the profile (Punta
Prima) respect to the town of Torrevieja. These movements could be related to the activity of the Bajo Segura and the San
Miguel faults respectively. Using geological markers we have deduced uplift rates of 0.1 mm/year during the last 3 million
years. Therefore, these preliminary results indicate that geodetically (short-term deformation) determined uplift rates are
similar to those estimated from geological markers (long term deformation). 相似文献
194.
Vidal Javier Marcé Rafael Serra Teresa Colomer Jordi Rueda Francisco Casamitjana Xavier 《Aquatic Sciences - Research Across Boundaries》2012,74(2):315-327
The local response of the phytoplankton community to river inflow processes was investigated with modeling and field analyses
in a long and narrow, stratified reservoir in mid-summer. The river water had high concentrations of phosphorus and nitrogen
(ammonium and nitrate) and temperature had large variations at diurnal scales. As a consequence of the large variation in
river temperature, the level of neutral buoyancy (the depth where the river water spreads laterally in the reservoir) oscillated
between the surface (overflows) during the day, and the depth of the metalimnion (interflows) during the night. The reservoir
remained strongly stratified, which favoured the presence of cyanobacteria. It is shown that under these conditions, nutrient-rich
river water injected during overflows into the surface layers promoted the occurrence of localized algal blooms in the zones
where the overflow mixed with the quiescent water of the reservoir. A series of hydrodynamic simulations of the reservoir
were conducted both with synthetic and realistic forcing to assess the importance of river temperatures and wind-driven hydrodynamics
for algal blooms. The simulations confirmed that the river inflow was the main forcing mechanism generating the localized
bloom. 相似文献
195.
In wetlands wind-induced turbulence significantly affects the bottom boundary, and the interaction between turbulence and plant canopies is therefore particularly important. The aim of this study is to advance understanding of the impact of this interaction in submerged aquatic vegetation (SAV)1 on vertical mixing in a fluid dominated by turbulence. Wind-generated turbulence was simulated in the laboratory using an oscillating grid. We quantify the vertical distribution of turbulent kinetic energy (TKE)2 above and within different types of vegetation, measured by an acoustic Doppler velocimeter. Experimental conditions are analysed in two canopy models (rigid and semi-rigid) with seven solid plant fractions (SPFs)3, three stem diameters (d)4 and three oscillation grid frequencies (f)5 and four natural SAVs (Cladium mariscus, Potamogeton nodosus, Myriophyllum verticillatum and Ruppia maritima). 相似文献
196.
Josep MaTRIGO‐RODRIGUEZ Juan Fabregat Jordi Llorca 《Meteoritics & planetary science》2001,36(12):1597-1604
Abstract— The Leonid meteor shower was observed worldwide in 1998 November in an intensive campaign without precedent. During this international effort ~35 500 meteors were reported by members and collaborators of the International Meteor Organization (IMO) using a standard methodology. Despite the absence of a meteor storm in 1998, the rich observational data allow us to obtain a detailed unprecedented knowledge of the stream structure between 1994 and 1998. 相似文献
197.
Xavier Casamitjana Jordi Colomer Harindra J. S. Fernando 《Aquatic Sciences - Research Across Boundaries》2000,62(1):79-90
198.
Enrique Peña González Joaquín Suárez López Jordi Delgado Martín Alfredo Jácome Burgos Jerónimo Puertas Agudo 《Environmental Geology》2006,50(6):823-834
The cutting operations of dimension stone at quarries produce a large amount of fines that, in turn, cause a negative environmental impact over local surface waters. This article presents a detailed analysis of the mobilized contamination associated with runoff waters in a large granite quarry (~200 ha) which is located in Porriño (Galicia, NW Spain), the most important production centre of dimension stone in Spain. There, an intensive monitoring survey was developed in order to characterize the hydrology of the system as well as the release and transport of pollutants. This was accomplished by means of different control sections for the flow and by the collection of 52 random water samples. Automatic samplers were also used to collect 192 water samples associated with runoff generated by significant rain events. For each of the samples collected, a wide battery of analytic determinations was performed, including solid loads, turbidity, organic pollution, nutrient and selected metals. Upon careful examination it has been possible to obtain different parameters related to the contamination control, like the “event mean concentration” (EMC), maximum concentrations and specific sediment loads. Moreover, a comprehensive statistical study including parameter correlation and cumulative probability analyses helped to understand the pollutant mobilization behaviour within the quarry system. It can be concluded that mobilized contamination shows the anomalous presence of some metals, whose concentrations are in excess when compared to the natural rock. This excess metal amount must be attributed to an anthropogenic source associated to mining and cutting operations. 相似文献
199.
200.
Jordi A Ferrer MI Vizoso G Orfila A Basterretxea G Casas B Alvarez A Roig D Garau B Martínez M Fernández V Fornés A Ruiz M Fornós JJ Balaguer P Duarte CM Rodríguez I Alvarez E Onken R Orfila P Tintoré J 《Marine pollution bulletin》2006,53(5-7):361-368
The oil spill from Prestige tanker showed the importance of scientifically based protocols to minimize the impacts on the environment. In this work, we describe a new forecasting system to predict oil spill trajectories and their potential impacts on the coastal zone. The system is formed of three main interconnected modules that address different capabilities: (1) an operational circulation sub-system that includes nested models at different scales, data collection with near-real time assimilation, new tools for initialization or assimilation based on genetic algorithms and feature-oriented strategic sampling; (2) an oil spill coastal sub-system that allows simulation of the trajectories and fate of spilled oil together with evaluation of coastal zone vulnerability using environmental sensitivity indexes; (3) a risk management sub-system for decision support based on GIS technology. The system is applied to the Mediterranean Sea where surface currents are highly variable in space and time, and interactions between local, sub-basin and basin scale increase the non-linear interactions effects which need to be adequately resolved at each one of the intervening scales. Besides the Mediterranean Sea is a complex reduced scale ocean representing a real scientific and technological challenge for operational oceanography and particularly for oil spill response and search and rescue operations. 相似文献