64 research outputs found
A tailored multi-model ensemble for air traffic management: Demonstration and evaluation for the Eyjafjallajökull eruption in May 2010
High quality volcanic ash forecasts are crucial to minimize the economic impact of volcanic hazards on air traffic. Decision-making is usually based on numerical dispersion modeling with only one model realization. Given the inherent uncertainty of such approach, a multi-model multi-source term ensemble has been designed and evaluated for the Eyjafjallajökull eruption in May 2010. Its use for air traffic management is discussed. Two multi-model ensembles were built: the first is based on the output of four dispersion models and their own implementation of ash ejection. All a priori model source terms were constrained by observational evidence of the volcanic ash cloud top as a function of time. The second ensemble is based on the same four dispersion models, which were run with three additional source terms: (i) a source term obtained with background modeling constrained with satellite data (a posteriori source term), (ii) its lower bound estimate, and (iii) its upper bound estimate. The a priori ensemble gives valuable information about the probability of ash dispersion during the early phase of the eruption, when observational evidence is limited. However, its evaluation with observational data reveals lower quality compared to the second ensemble. While the second ensemble ash column load and ash horizontal location compare well to satellite observations, 3D ash concentrations are negatively biased. This might be caused by the vertical distribution of ash, which is too much diluted in all model runs, probably due to defaults in the a posteriori source term and vertical transport and/or diffusion processes in all models. Relevant products for the air traffic management are horizontal maps of ash concentration quantiles (median, 75 %, 99 %) at a fine-resolved flight level grid. These maps can be used for route optimization in the areas where ash does not pose a direct and urgent threat to aviation. Cost-optimized consideration of such hazards will result in much less impact on flight cancellations, reroutings, and traffic flow congestions.</p
Received Date: 05-Sep-2013 Accepted Article Revised Date: 08-Nov-2013 Accepted Date: 19-Nov-2013 Article type: Original Article SPATIOTEMPORAL CHANGES IN THE GENETIC DIVERSITY OF HARMFUL ALGAL BLOOMS CAUSED BY THE TOXIC DINOFLAGELLATE ALEXANDRIUM MINUTUM
Running title: A. minutum spatiotemporal genetic diversit
High-resolution electron-microscopic study of the relationship between human enamel and dentin crystals at the dentinoenamel junction
Intercomparison of four remote-sensing-based energy balance methods to retrieve surface evapotranspiration and water stress of irrigated fields in semi-arid climate
Instantaneous evapotranspiration rates and surface water stress levels can
be deduced from remotely sensed surface temperature data through the surface
energy budget. Two families of methods can be defined: the contextual
methods, where stress levels are scaled on a given image between hot/dry and
cool/wet pixels for a particular vegetation cover, and single-pixel methods,
which evaluate latent heat as the residual of the surface energy balance for
one pixel independently from the others. Four models, two contextual (S-SEBI
and a modified triangle method, named VIT) and two single-pixel (TSEB, SEBS)
are applied over one growing season (December–May) for a 4 km × 4 km
irrigated agricultural area in the semi-arid northern Mexico. Their
performance, both at local and spatial standpoints, are compared relatively
to energy balance data acquired at seven locations within the area, as well
as an uncalibrated soil–vegetation–atmosphere transfer (SVAT) model forced
with local in situ data including observed irrigation and rainfall amounts.
Stress levels are not always well retrieved by most models, but S-SEBI as
well as TSEB, although slightly biased, show good performance. The drop in
model performance is observed for all models when vegetation is senescent,
mostly due to a poor partitioning both between turbulent fluxes and between
the soil/plant components of the latent heat flux and the available energy.
As expected, contextual methods perform well when contrasted soil moisture
and vegetation conditions are encountered in the same image (therefore,
especially in spring and early summer) while they tend to exaggerate the
spread in water status in more homogeneous conditions (especially in
winter). Surface energy balance models run with available remotely sensed
products prove to be nearly as accurate as the uncalibrated SVAT model
forced with in situ data
Attitudes about dental care among parents whose children suffer from severe congenital heart disease: a case-control study
An ensemble of state-of-the-art ash dispersion models: towards probabilistic forecasts to increase the resilience of air traffic against volcanic eruptions
High-quality volcanic ash forecasts are crucial to
minimize the economic impact of volcanic hazards on air
traffic. Decision-making is usually based on numerical dispersion modelling with only one model realization. Given
the inherent uncertainty of such an approach, a multi-model
multi-source term ensemble has been designed and evaluated for the Eyjafjallajökull eruption in May 2010. Its use for flight planning is discussed. Two multi-model ensembles were built: the first is based on the output of four dispersion models and their own implementation of ash ejection
Dental caries experience in children with congenital heart disease: a case-control study
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