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Abstract When conducting large‐eddy simulations (LESs) of plume dispersion in the atmosphere, crucial issue is to prescribe time‐dependent turbulent inflow data. Therefore, several techniques for driving LESs have been proposed. For example, in the original recycling (OR) method developed by Kataoka and Mizuno (Wind and Structures, 2002, 5, 379–392), a mean wind profile is prescribed at the inlet boundary, the only fluctuating components extracted at the downstream position are recycled to the inlet boundary. Although the basic turbulence characteristics are reproduced with a short development section, it is difficult to generate target turbulent fluctuations consistent with realistic atmospheric turbulence. In this study, we proposed a dynamically controlled recycling (DCR) method that is a simple extension of the OR procedure. In this method, the magnitude of turbulent fluctuations is dynamically controlled to match with the target turbulent boundary layer (TBL) flow using a turbulence enhancement coefficient based on the ratio of the target turbulence statistics to the computed ones. When compared to the recommended data of Engineering Science Data Unit (ESDU) 85020, the turbulence characteristics generated by our proposed method were quantitatively reproduced well. Furthermore, the spanwise and vertical plume spreads were also simulated well. It is concluded that the DCR method successfully simulates plume dispersion in neutral TBL flows.

A multiscale numerical framework has been developed to investigate the dispersion of deep-sea hydrothermal plumes that originate from the Endeavour Segment of the Juan de Fuca Ridge located in the Northeast Pacific. The analysis of simulation outputs presented in this study provides insights into the influences of tidal forcing and the buoyancy flux associated with hydrothermal venting on ocean circulation and plume dispersion in the presence of pronounced seafloor topography. The results indicate that tidal forcing drives anti-cyclonic circulation near the ridge-axis, while hydrothermal venting induces cyclonic circulation around vent fields within the axial rift valley. Tidal forcing has a notable impact on plume dispersion, particularly near the large topographic features to the north of the Endeavour Segment. Furthermore, plume dispersion exhibits notable inter-annual variability, with a northbound trajectory in 2016 and a southbound trajectory in 2021. The study also reveals that both buoyancy fluxes and tidal forcing enhance the mixing of hydrothermal plumes with ambient seawater.

Hydrothermal vents are a source of many trace metals to the oceans. Compared to mid-ocean ridges, hydrothermal vent systems at arcs occur in shallower water depth and are much more diverse in fluid composition, resulting in highly variable water column trace metal concentrations. However, only few studies have focused on trace metal dynamics in hydrothermal plumes at volcanic arcs. During R/V Sonne cruise SO253 in 2016/2017, hydrothermal plumes from two hydrothermally active submarine volcanoes along the Kermadec arc in the Southwest Pacific Ocean were sampled: (1) Macauley, a magmatic dominated vent site located in water depths between 300 and 680 m, and (2) Brothers, located between 1,200 and 1,600 m water depth, where hydrothermalism influenced by water rock interactions and magmatically influenced vent sites occur near each other. Surface currents estimated from satellite-altimeter derived currents and direct measurements at the sites using lowered acoustic Doppler current profilers indicate the oceanic regime is dominated by mesoscale eddies. At both volcanoes, results indicated strong plumes of dissolved trace metals, notably Mn, Fe, Co, Ni, Cu, Zn, Cd, La, and Pb, some of which are essential micronutrients. Dissolved metal concentrations commonly decreased with distance from the vents, as to be expected, however, certain element/Fe ratios increased, suggesting a higher solubility of these elements and/or their stronger stabilization (e.g., for Zn compared to Fe). Our data indicate that at the magmatically influenced Macauley and Brothers cone sites, the transport of trace metals is strongly controlled by sulfide nanoparticles, while at the Brothers NW caldera wall site iron oxyhydroxides seem to dominate the trace metal transport over sulfides. Solution stabilization of trace metals by organic complexation appears to compete with particle adsorption processes. As well as extending the generally sparse data set for hydrothermal plumes at volcanic arc systems, our study presents the first data on several dissolved trace metals in the Macauley system, and extends the existing plume dataset of Brothers volcano. Our data further indicate that chemical signatures and processes at arc volcanoes are highly diverse, even on small scales.

A gas well blowout in south central Texas in November 2019 that lasted for 20 days provided a unique opportunity to test the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model’s plume dispersion against hydrocarbon air monitoring data at two nearby state monitoring stations. We estimated daily blowout hydrocarbon emission rates from satellite measurement-based results on methane emissions in conjunction with previously reported composition data of the local hydrocarbon resource. Using highly elevated hydrocarbon mixing ratios observed during several days at the two downwind monitoring stations, we calculated excess abundances above expected local background mixing ratios. Subsequent comparisons to HYSPLIT plume dispersion model outputs, generated using High-Resolution Rapid Refresh (HRRR) or North American Mesoscale (NAM) forecast meteorological input data, showed that the model generally reproduces both the timing and magnitude of the plume in various meteorological conditions. Absolute hydrocarbon mixing ratios could typically be reproduced within a factor of two. However, when lower emission rate estimates provided by the company in charge of the well were used, downwind hydrocarbon observations could not be reproduced. Overall, our results suggest that HYSPLIT, in combination with high-resolution meteorological input data, is a useful tool to accurately forecast chemical plume dispersion and potential human exposure in disaster situations.

The flow vectors of radioactive cesium-137 (137Cs) plume emitted from the Fukushima Daiichi nuclear power plant in March 2011 were quantitatively depicted by a mass flux analysis in this study. 137Cs plumes were calculated by an Eulerian dispersion model with a 3-km horizontal resolution. The vertically column-integrated mass flux was consistent with the flow approximation based on ground surface 137Cs observations, even though there were some discrepancies that were caused by differences in the wind direction between the ground surface and the dominant plume layer. These discrepancies were explained by combining the use of the ground surface horizontal mass flux with the column-integrated mass flux. The mass flux analysis clearly provided an illustration of 137Cs dominant stream locations, directions, and depositions by reducing high-dimensional model outputs into a lower-dimensional plot. Mass flux (i.e. the product of the mass density and wind velocity) has often been used in dynamic meteorology but has not been used as frequently in atmospheric chemistry or pollutant dispersion studies. However, the concept of mass flux is a robust alternative for conventional validation approaches that only utilize a time series of pollutant concentrations. Mass flux analyses can be used further in atmospheric chemistry as a quantitative visualization tool to track the emission, advection, dispersion, and deposition of atmospheric constituents.

Contaminant gas dispersion within an urban area resulting from accidental or intentional release is of great concern to public health and social security. When estimating plume dispersion in a built-up urban area under real meteorological conditions by computational fluid dynamics (CFD), a crucial issue is how to prescribe the input conditions. There are typically two approaches: using the outputs of a mesoscale meteorological simulation (MMS) model and meteorological observations (OBS). However, the influences of the different approaches on the simulation results have not been fully demonstrated. In this study, we conducted large-eddy simulations (LESs) of plume dispersion in the urban central district of Oklahoma City under real meteorological conditions by coupling with a MMS model and OBS obtained at a single stationary point, and evaluated the two different coupling simulations in comparison with the field experiments. The LES–MMS coupling showed better performance than the LES–OBS one. The latter one also showed a reasonable performance comparable to the acceptance criteria on the model prediction within a factor of two of the experimental data. These facts indicate that the approach using observations at a single stationary point still has enough potential to drive CFD models for plume dispersion under real meteorological conditions.

We conducted single-model initial-perturbed ensemble simulations to quantify uncertainty in aerosol dispersion modeling, focusing on a point-source radioactive aerosol emitted from the Fukushima Daiichi Nuclear Power Plant (FDNPP) in March 2011. The ensembles of the meteorological variables were prepared using a data assimilation system that consisted of a non-hydrostatic weather-forecast model with a 3-km horizontal resolution and a four-dimensional local ensemble transform Kalman filter (4D-LETKF) with 20 ensemble members. The emission of radioactive aerosol was not perturbed. The weather and aerosol simulations were validated with in-situ measurements at Hitachi and Tokai, respectively, approximately 100 km south of the FDNPP. The ensemble simulations provided probabilistic information and multiple case scenarios for the radioactive aerosol plumes. Some of the ensemble members successfully reproduced the arrival time and intensity of the radioactive aerosol plumes, even when the deterministic simulation failed to reproduce them. We found that a small ensemble spread of wind speed produced large uncertainties in aerosol concentrations.

We present wind data collected for ten days during the dry season in 2008 during the Murici II Campaign, which was carried out in the area of the Centro de Lançamento de Alcântara (CLA). The main goals are to better understand processes governing the wind regime in the CLA and the development of tools for analyzing the impact of wind on rocket structure and on the dispersion of pollutants released during the launch. A set of 11 aerovanes (ten at 10-m height and one at 1.5-m height) plus a sonic anemometer at 1.5-m height were deployed to measure wind speed and direction, which were stored as ten-minute data. Turbulence intensity, gust factor, and gust amplitude were computed from the available dataset. Statistical analysis shows that the wind direction is predominant from East-Northeast (ENE), with the mean vector wind direction of 60o, in agreement with the trade wind regime. The diurnal cycle of all statistical properties of the wind are strongly marked. Wind speed, turbulence intensity, and gusts are peaked at about 1000 LST. The presence of a non-diurnal cycle of four days has been noticed and might be associated with synoptic systems acting on the region. A simple heuristic formula was proposed to compute Lagrangian time-scale from Eulerian time-scale, and from which we compute the Lagragian standard deviation, a final product to be used as input in diffusion models.

The overall focus of the research work was to study the various factors that affect plume dilution anddispersion. Some of the factors that were studied include; the effects of mixing height, the effects of plume riseand the effects of terrain in addition to momentum and buoyancy on the overall dispersion of plume releasedfrom a stack of known effective height. Data on temperature versus altitude was collected using an infra - redthermometer at different height of a telecommunication mast under construction. The highest temperature forthe month was noted and the validity of the recorded data was done using correlation analysis. Mathematicalanalysis was then employed to determine the mixing depth which represents the effective height of any stackthat must be placed in such location in other to allow for complete dispersion/dilution of any form of pollutantreleased from any source. Result obtained shows that the effective height of stack that can be erected in suchlocation that will allow for effective dispersion of any pollutants was shown to be 1700m. Any stack below thisheight will lead to ground level pollution. Also discussed in this research paper is the application of GaussianPlume model in the evaluation/analysis of the horizontal dispersion of pollutants released from a height (h).