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•NPP simulation accuracy is improved by using wCASA model with R2 increased by 9.59%.•Future NPP projection using the wCASA model is achieved.•Future NPP in Xinjiang shows an upward ...trend for grassland and a downward trend for cropland.
Net Primary Productivity (NPP) is an important component of the carbon cycle of terrestrial ecosystems and plays an important role in the evaluation of vegetation growth. Among all the factors, wind also plays a vital role in modeling vegetation productivity. However, none of the current models have considered the impact of wind on the process of productivity estimation. An in-depth study was conducted on the temporal and spatial distribution and internal relations between wind speed and NPP. By introducing the influence factor wind, the Carnegie-Ames-Stanford model (CASA) based on the land-surface water index was modified and named as wCASA model. The estimation and prediction results of wCASA model considering the influence factor wind were better than that of the CASA model. The modified wCASA model was applied in Xinjiang, China. The simulation results were improved with the coefficient of determination (R2) increased by 9.59%, the root mean square error (RMSE) decreased by 13.78%, and the residual of prediction deviation (RPD) improved by 12.08% as compared to CASA model. The optimal model was used to simulate and predict the NPP of cropland and grassland for 2022–2050 under three climate scenarios, SSP126, SSP245, and SSP585, respectively, based on the CMIP6 dataset. The wCASA model can accurately estimate and predict NPP, which provides scientific basis for efficient agricultural water use and food production.
Hazardous areas are defined as a result of a variety of variables as storage temperature, pressure, leak orifice size, physical properties of flammable substance, and wind characteristics. The ...potential formation of an explosive atmosphere must be accurately assessed to ensure process safety. Therefore, computational fluid dynamics (CFD) arises as an important tool for accurate predictions as recommended by the international standard IEC 60079-10-1 (2015). This study aims to analyze the influence of wind velocity magnitude and direction on the hazardous area classification. The authors evaluated the extent and volume for methane, propane, and hydrogen leakages from a CFD model. For each flammable gas, the wind velocity magnitude and direction were regularly varied. The outcomes show that the behavior of the plume size as the wind varies mainly depends on the gas concentration. Counter-flow wind directions lead to zero relative velocity closer to the release point, which concentrates the gas, and wind in the release direction promotes a higher dilution of the gas cloud increasing the hazardous extent while decreases the volume. As a consequence, the wind also influences the zone type, which was accurately predicted from CFD simulations and significant differences were found when compared to the standard analyses. These differences are, to some extent, related to the consideration of wind velocity effects on the gas jet release.
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•CFD simulations predict compressible gas emission and dispersion.•Wind velocity has an important effect on hazardous distance of flammables.•The behavior of the gas cloud extent and volume depends on the gas concentration.•Wind speed and direction affect the zone type of hazardous area classification.
Wind patterns shape migratory pathways and detours of many procellariiform bird species that seasonally migrate between hemispheres. These seabirds are long-lived, and the period of immaturity is ...presumed to be a time of development and learning the environment, specifically how to use wind to their advantage. We assess how wind encountered by individual Great Shearwaters (
Ardenna gravis
) varies along the migration journey and compare responses between presumed mature and immature birds (early and late, respectively) in southbound migration and mature birds in northbound migration. We analyze modeled Argos locations from 71 individual tracks of migratory Great Shearwaters with concurrent U (East/West) and V (North/South) wind components. Migration in seabirds is well studied, but there is limited quantitative work measuring individual birds directly interacting with wind and their associated changes in flight behavior during migration. We show that Great Shearwaters made optimal use of winds, and that different age groups made decisions that exposed them to different wind constraints. Overall, Great Shearwaters derived positive responses from wind under most conditions and did not rely on a drifting strategy, which would be suggested if wind effect (difference between ground and airspeed) was predominantly positive during migrations. Instead, they appeared to use a compensating strategy to achieve an acceptable course and speed. The difference we observed in migration phenologies suggests that by migrating later, immature birds might travel the
path of least resistance
and experience flight conditions that are less risky furthering their ability to withstand a variety of wind conditions encountered later in life as done by adults, which migrate earlier and are subject to more variable flight conditions. We conclude that like other procellariiforms, a longer period of sexual maturity is required to enhance flight performance and mediate energy expenditure through experiential learning and increased fitness.
Wind influence on a coastal buoyant outflow Whitney, Michael M.; Garvine, Richard W.
Journal of Geophysical Research - Oceans,
March 2005, Volume:
110, Issue:
C3
Journal Article
Peer reviewed
This paper investigates the interplay between river discharge and winds in forcing coastal buoyant outflows. During light winds a plume influenced by the Earth's rotation will flow down shelf (in the ...direction of Kelvin wave propagation) as a slender buoyancy‐driven coastal current. Downwelling favorable winds augment this down‐shelf flow, narrow the plume, and mix the water column. Upwelling favorable winds drive currents that counter the buoyancy‐driven flow, spread plume waters offshore, and rapidly mix buoyant waters. Two criteria are developed to assess the wind influence on a buoyant outflow. The wind strength index (Ws) determines whether a plume's along‐shelf flow is in a wind‐driven or buoyancy‐driven state. Ws is the ratio of the wind‐driven and buoyancy‐driven along‐shelf velocities. Wind influence on across‐shelf plume structure is rated with a timescale (ttilt) for the isopycnal tilting caused by wind‐driven Ekman circulation. These criteria are used to characterize wind influence on the Delaware Coastal Current and can be applied to other coastal buoyant outflows. The Delaware buoyant outflow is simulated for springtime high–river discharge conditions. Simulation results and Ws values reveal that the coastal current is buoyancy‐driven most of the time (∣Ws∣ < 1 on average). Wind events, however, overwhelm the buoyancy‐driven flow (∣Ws∣ > 1) several times during the high‐discharge period. Strong upwelling events reverse the buoyant outflow; they constitute an important mechanism for transporting fresh water up shelf. Across‐shelf plume structure is more sensitive to wind influence than the along‐shelf flow. Values of ttilt indicate that moderate or strong winds persisting throughout a day can modify plume width significantly. Plume widening during upwelling events is accompanied by mixing that can erase the buoyant outflow.
Birds: blowin’ by the wind? Liechti, Felix
Journal of ornithology,
04/2006, Volume:
147, Issue:
2
Journal Article
Peer reviewed
Migration is a task that implies a route, a goal and a period of time. To achieve this task, it requires orientation abilities to find the goal and energy to cover the distance. Completing such a ...journey by flying through a moving airspace makes this relatively simple task rather complex. On the one hand birds have to avoid wind drift or have to compensate for displacements to reach the expected goal. On the other hand flight costs make up a large proportion of energy expenditure during migration and, consequently, have a decisive impact on the refuelling requirements and the time needed for migration. As wind speeds are of the same order of magnitude as birds’ air speeds, flight costs can easily be doubled or, conversely, halved by wind effects. Many studies have investigated how birds should or actually do react to winds aloft, how they avoid additional costs or how they profit from the winds for their journeys. This review brings together numerous theoretical and empirical studies investigating the flight behaviour of migratory birds in relation to the wind. The results of these studies corroborate that birds select for favourable wind conditions both at departure and aloft to save energy and that for some long-distance migrants a tail-wind is an indispensable support to cover large barriers. Compensation of lateral wind drift seems to vary between age classes, depending on their orientation capacities, and probably between species or populations, due to the variety of winds they face en route. In addition, it is discussed how birds might measure winds aloft, and how flight behaviour with respect to wind shall be tested with field data.
In this paper, we investigate the water renewal of a highly populated marina, located in the south-west of France, and subjected to a macro-tidal regime. With the use of a 3D-numerical model ...(TELEMAC-3D), three water transport timescales were studied and compared to provide a fully detailed description of the physical processes occurring in the marina. Integrated Flushing times (IFT) were computed through a Eulerian way while a Lagrangian method allowed to estimate Residence Times (RT) and Exposure Times (ET). From these timescales, the return-flow (the fraction of water that re-enters the marina at flood after leaving the domain at ebb) was quantified via the Return-flow Factor (RFF) and the Return Coefficient (RC) parameters. The intrinsic information contained in these parameters is thoroughly analysed, and their relevance is discussed. A wide range of weather-marine conditions was tested to provide the most exhaustive information about the processes occurring in the marina. The results highlight the significant influence of the tide and the wind as well as the smaller influence of the Floating Structures (FS) on the renewal. Besides, this study provides the first investigation of the water exchange processes of La Rochelle marina. It offers some content that interest researchers and environmental managers in the monitoring of pollutants as well as biological/ecological applications.
Ship manoeuvrability is a wide term which consist of number of various parameters. Knowing the influence of these parameters on ship manoeuvrability is a first condition to ensure and maintain safe ...navigation. However, many of these parameters are external forces and, in some cases, cannot be calculated and prediction may be complicated. Analysing the influence of external forces can give as an insight into ship manoeuvrability when such external force occurs. The main purpose of this paper is to analyse the influence of wind on ship manoeuvrability. The best way to make such analysis is during turning circle because in this case wind acts in all 360°. Analysis is made using empirical equations and in situ with the real vessel. The results provide the better understanding of vessel trajectory and show that in some cases vessel may respond in unexpected manner.
To test the potential effects of winds on the migratory detours of shearwaters, transequatorial migrations of 3 shearwaters, the ManxPuffinus puffinus, the Cory’sCalonectris diomedea, and the Cape ...VerdeC. edwardsiishearwaters were tracked using geolocators. Concurrent data on the direction and strength of winds were obtained from the NASA SeaWinds scatterometer to calculate daily impedance models reflecting the resistance of sea surface winds to the shearwater movements. From these models we estimated relative wind-mediated costs for the observed synthesis pathway obtained from tracked birds, for the shortest distance pathway and for other simulated alternative pathways for every day of the migration period. We also estimated daily trajectories of the minimum cost pathway and compared distance and relative costs of all pathways. Shearwaters followed 26 to 52% longer pathways than the shortest distance path. In general, estimated wind-mediated costs of both observed synthesis and simulated alternative pathways were strongly dependent on the date of departure. Costs of observed synthesis pathways were about 15% greater than the synthesis pathway with the minimum cost, but, in the Cory’s and the Cape Verde shearwaters, these pathways were on average 15 to 20% shorter in distance, suggesting the extra costs of the observed pathways are compensated by saving about 2 travelling days. In Manx shearwaters, however, the distance of the observed synthesis pathway was 25% longer than that of the lowest cost synthesis pathway, probably because birds avoided shorter but potentially more turbulent pathways. Our results suggest that winds are a major determinant of the migratory routes of seabirds.
Geophysical, environmental, and urban fluid flows (i.e., flows developing in oceans, seas, estuaries, rivers, aquifers, reservoirs, etc.) exhibit a wide range of reactive and transport processes. ...Therefore, identifying key phenomena, understanding their relative importance, and establishing causal relationships between them is no trivial task. Analysis of primitive variables (e.g., velocity components, pressure, temperature, concentration) is not always conducive to the most fruitful interpretations. Examining auxiliary variables introduced for diagnostic purposes is an option worth considering. In this respect, tracer and timescale methods are proving to be very effective. Such methods can help address questions such as, "where does a fluid-born dissolved or particulate substance come from and where will it go?" or, "how fast are the transport and reaction phenomena controlling the appearance and disappearance such substances?" These issues have been dealt with since the 19th century, essentially by means of ad hoc approaches. However, over the past three decades, methods resting on solid theoretical foundations have been developed, which permit the evaluation of tracer concentrations and diagnostic timescales (age, residence/exposure time, etc.) across space and time and using numerical models and field data. This book comprises research and review articles, introducing state-of-the-art diagnostic theories and their applications to domains ranging from shallow human-made reservoirs to lakes, river networks, marine domains, and subsurface flows
Numerical models have been widely used to simulate and predict the behavior and transport of oil spills in marine environments. Their behavior is governed by physical, chemical and biological ...processes which are related to the hydrocarbon properties, hydrodynamic and weather conditions, and other environmental variables. The transport and interactions of oil particles were evaluated in simulations reproducing two oil spills recorded in the northern part of the Southern Brazilian Shelf (SBS). The numerical simulations were performed using the ECOS (Easy Coupling Oil System) model coupled to the three-dimensional hydrodynamic module TELEMAC3D. The hydrodynamic model provides the variables needed by oil spill model to calculate and infer the properties and behavior of the oil slick. The results indicate that the local wind forcing is the most important factor in determining the oil fate, followed by the intensities and directions of coastal currents. Regarding the events, in 2012 the oil reached the coast after 10 hours of the leak while in 2014 it was transported towards the ocean. The simulation strategy used in this article did not prove to be appropriate for estimates of the oil risk in the region, due to the distinct susceptibility responses between the events simulated.
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