Search

The 2010 Eyjafjallajökull volcano eruption had serious consequences to civil aviation. This has initiated a lot of research on volcanic ash transport forecast in recent years. For forecasting the volcanic ash transport after eruption onset, a volcanic ash transport and diffusion model (VATDM) needs to be run with Eruption Source Parameters (ESP) such as plume height and mass eruption rate as input, and with data assimilation techniques to continuously improve the initial conditions of the forecast. Reliable and accurate ash measurements are crucial for providing a successful ash clouds advice. In this paper, simulated aircraft-based measurements, as one type of volcanic ash measurements, will be assimilated into a transport model to identify the potential benefit of this kind of observations in an assimilation system. The results show assimilating aircraft-based measurements can significantly improve the state of ash clouds, and further providing an improved forecast as aviation advice. We also show that for advice of aeroplane flying level, aircraft-based measurements should be preferably taken from this level to obtain the best performance on it. Furthermore it is shown that in order to make an acceptable advice for aviation decision makers, accurate knowledge about uncertainties of ESPs and measurements is of great importance. [ABSTRACT FROM AUTHOR]

Workplace-related factors are associated with the risk of depression. Despite implementation of workplace health promotion (WHP) programmes in China to promote the physical and mental well-being of workers, the relationship between WHP and depression has received limited attention. This study investigated the association between WHP service utilisation and depressive symptoms among workers. This was a cross-sectional survey. A researcher-designed questionnaire was used to collect information on socio-demographic and occupational characteristics, WHP service utilisation, and mental health status. The Lasso method was used for variable selection to achieve dimension reduction, and logistic regression was used to assess the association between WHP service utilisation and depressive symptoms. The analysis included 11,710 workers, of whom 17.0% had depressive symptoms. Lasso regression resulted in 6 of 18 WHP services showing significant negative associations with depressive symptoms, including occupational safety training, mental health services, health check-ups, sports activities, fitness rooms, and healthy canteens. The logistic regression results showed that, after adjusting for sociodemographic and occupational factors, utilisation of these six services was associated with a decreased likelihood of depressive symptoms. The adjusted odds ratio (aOR) was 0.84 (95% confidence interval [CI]: 0.73–0.96) for occupational safety training, aOR: 0.82 (95% CI: 0.68–0.99) for mental health services, aOR: 0.80 (95% CI: 0.71–0.90) for health check-ups, aOR: 0.68 (95% CI: 0.57–0.80) for sports activities, aOR: 0.59 (95% CI: 0.47–0.74) for fitness rooms and aOR: 0.72 (95% CI: 0.59–0.87) for healthy canteens. Utilisation of WHP services was associated with a lower prevalence of depressive symptoms. Implementation of WHP services and the provision of a supportive workplace environment should be prioritised to benefit the mental health of workers. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the simulation of transport of pollutants in shallow water using random walk models and develops several computation techniques to speed up the numerical integration of the stochastic differential equations (SDEs). This is achieved by using both random time stepping and parallel processing. We start by considering a basic stochastic Euler scheme for integration of the diffusion and drift terms of the SDEs, with a strong order 1 in the strong sense. The errors due to this scheme depend on the location of the pollutant; it is dominated by the diffusion term near boundaries, and by the deterministic drift further away from the boundaries. Using a pair of integration schemes, one of strong order 1.5 near the boundary and one of strong order 2.0 elsewhere, we can estimate the error and approximate an optimal step size for a given error tolerance. The resulting algorithm is developed such that it allows for complete flexibility of the step size, while guaranteeing the correct Brownian behaviour. Modelling pollutants by non-interacting particles enables the use of parallel processing in the simulation. We take advantage of this by implementing the algorithm using the MPI library. The inherent asynchronic nature of the particle simulation, in addition to the parallel processing, makes it difficult to get a coherent picture of the results at any given points. However, by inserting internal synchronisation points in the temporal discretisation, the code allows pollution snapshots and particle counts to be made at times specified by the user. [Copyright &y& Elsevier]

Worldwide, billions of people rely on fresh groundwater reserves for their domestic, agricultural and industrial water use. Extreme droughts and excessive groundwater pumping put pressure on water authorities in maintaining sustainable water usage. High-resolution integrated models are valuable assets in supporting them. The Netherlands Hydrological Instrument (NHI) provides the Dutch water authorities with open source modeling software and data. However, NHI integrated groundwater models often require long run times and large memory usage, therefore strongly limiting their application. As a solution, we present a distributed memory parallelization, focusing on the National Hydrological Model. Depending on the level of integration, we show that significant speedups can be obtained up to two orders of magnitude. As far as we know, this is the first reported integrated groundwater parallelization of an operational hydrological model used for national-scale integrated water management and policy making. The parallel model code and data are freely available. [ABSTRACT FROM AUTHOR]

• SEAWAT is parallelized using a MPI distributed memory approach. • Huge 3D SEAWAT models are now feasible for a wide range of users. • For a hypothetical and a real-life test case we report speedups up to two orders. Fresh groundwater reserves, being of vital importance for more than a billion of people living in the coastal zone, are being threatened by saltwater intrusion due to anthropogenic activities and climate change. High resolution three-dimensional (3D), variable-density (VD), groundwater flow and salt transport (FT) numerical models are increasingly being used to support water managers and decision makers in their strategic planning and measures for dealing with the problem of fresh water shortages. However, these computer models typically require long runtimes and large memory usage, making them impractical to use without parallelization. Here, we parallelize SEAWAT, and show that with our parallelization 3D-VD-FT modeling is now feasible for a wide range of hydrogeologists, since a) speedups of more than two orders of magnitude can be obtained as illustrated in this paper, and b) large 3D-VD-FT models are feasible with memory requirements far exceeding single machine memory. [ABSTRACT FROM AUTHOR]