Timing of hurricane emergency actions

Emergency actions to prepare for hurricanes often require more time than is available from official public warnings. This means that the preparedness official must decide not onlywhat to do butwhen to do it. The action decision system, described here, developed for use in the State of Florida, reformats the hurricane track forecast, a 72-h projection, prepared at the National Hurricane Center in Miami, to specify the probability of a strike at each of 12 vulnerable coastal communities, and then normalizes the value in terms of a composite of probabilities computed for historic hurricanes that struck the respective communities. The normalization, a ratio of the two probability values, current and historic, expressed as a percentage is defined as the level of risk. When this level reaches or exceeds 100% the risk level is defined as critical and the system recommends that emergency actions to prepare begin immediately.The system is founded upon individual hurricane climatologies and decision procedures that are tailored for use at each community. The action recommendations generated by the risk analyses with a 93% level of confidence relieve the preparedness official of the need to make meteorological decisions in timing evacuations and other critical measures, even when these must begin before official hurricane warnings are received.The work that provided the basis for this publication was supported by funding under a Cooperative Agreement with the Federal Emergency Management Agency. The substance and findings of the work are dedicated to the public. The authors are solely responsible for the accuracy of the statements and interpretations contained in the publication. Such interpretations do not necessarily reflect the views of the government.     

A Risk-Based Predictive Tool to Prevent Accidental Introductions of Nonindigenous Marine Species

Preventing the introduction of nonindigenous species (NIS) is the most efficient way to avoid the costs and impacts of biological invasions. The transport of fouling species on ship hulls is an important vector for the introduction of marine NIS. We use quantitative risk screening techniques to develop a predictive tool of the abundance and variety of organisms being transported by ocean-going yachts. We developed and calibrated an ordinal rank scale of the abundance of fouling assemblages on the hulls of international yacht hulls arriving in New Zealand. Fouling ranks were allocated to 783 international yachts that arrived in New Zealand between 2002 and 2004. Classification tree analysis was used to identify relationships between the fouling ranks and predictor variables that described the maintenance and travel history of the yachts. The fouling ranks provided reliable indications of the actual abundance and variety of fouling assemblages on the yachts and identified most (60%) yachts that had fouling on their hulls. However, classification tree models explained comparatively little of the variation in the distribution of fouling ranks (22.1%), had high misclassification rates (∼43%), and low predictive power. In agreement with other studies, the best model selected the age of the toxic antifouling paint on yacht hulls as the principal risk factor for hull fouling. Our study shows that the transport probability of fouling organisms is the result of a complex suite of interacting factors and that large sample sizes will be needed for calibration of robust risk models.     

Residual gasoline saturation in unsaturated soil with and without organic matter

The goal of this study was to investigate the influence of one variable, natural organic matter, on residual gasoline saturation in sandy soils. Capillary pressure-saturation (P_c−S) relationships (air-gasoline) were determined for three physically-similar sandy soils, with different organic carbon contents (0.086%, 0.89% and 1.65%) and residual gasoline saturations were compared. Two initial moisture conditions, residual water saturation and air-dry, were evaluated. One soil type was packed to two different bulk densities. Visualization of the soils using cryo-scanning electron microscopy was performed to aid in better understanding the role of the organic matter in the soil. The results showed that soils with higher organic contents had higher residual gasoline saturations when starting with an initially air-dry soil. Increasing the bulk density of the same air-dried soil resulted in an increase in residual gasoline saturation. In the presence of a residual water saturation, however, residual gasoline saturations were virtually identical for the three soils and independent of bulk density; approximately 5–10 times lower than in soil that was initially air-dry. The presence of the residual water effectively coated the surface of the soil thereby reducing or eliminating gasoline/soil interactions. Some residual water may also be occupying very small pore spaces, making these locations inaccessible to the gasoline.     

Concentration field and turbulent fluxes during the mixing of two buoyant plumes

In this work an experimental study of mixing of two identical plumes, carried out in a turbulent neutral boundary layer generated in a wind tunnel, is presented. Measurements have been performed with fast flame ionisation detectors (FFIDs) and a two-component Laser-Doppler Anemometer system. Results allow the study of both the average and the fluctuating concentration field, including the turbulent vertical and longitudinal mass fluxes, in single plumes and during the interaction of two identical plumes. This information gives insight into the details of the mixing phase of the two plumes. Results of trajectories and additional rise (due to plume interactions) have been compared with previous measurements carried out in laminar cross-flows, showing similar behaviour. Concentration distributions in plume cross-sections in turbulent cross-flows differ from those measured in laminar cross-flows. Average vertical and longitudinal velocity measurements into the plume core show the strength of the shielding effect of the upwind plume and some details of interaction between the counter-rotating vortex pairs (CVPs). For large values of the alignment angle φ, between the line joining the stacks and the cross-flow, an average negative vertical velocity is measured in the middle of the plume even if its centre of mass is rising. This downward velocity is induced by the slow interaction of the CVPs and generates a vertical stretching of the plume and negative rise enhancement. Vertical turbulent fluxes change sign on the plume centreline and are of opposite sign with respect to the longitudinal turbulent fluxes. Results indicate a good linearity between vertical turbulent fluxes and concentration gradients, with different proportionality for the top and bottom parts of the plume (especially in the near field) indicating that dispersion could be described by a gradient-transfer model.     

Three-dimensional characterization of the ammonia plume from a beef cattle feedlot

In Canada approximately 45% of ammonia (NH₃) emissions are attributed to dairy and beef cattle industries. The present study focused on NH₃ emissions from a beef feedlot with a one-time capacity of 17,220 head. The aim was to improve the Canadian NH₃ emission inventories and air quality forecasting capabilities. A Cessna 207, equipped with a fast-response NH₃/NO_y detector and a quadrupole aerosol mass spectrometer, was flown in a grid pattern covering an area of 8 × 8 km centered on a feedlot (800 × 800 m) at altitudes ranging from 30 to 300 m above ground. Stationary ground measurements of NH₃ concentration and turbulence parameters were made downwind of the feedlot. Three flights were conducted under varying meteorological conditions, ranging from very calm to windy with near-neutral stratification. NH₃ mixing ratios up to 100 ppbv were recorded on the calm day, up to 300 m above ground. An average feedlot NH₃ emission rate of 76 ± 4 μg m^?2 s^?1 (equivalent to 10.2 g head^?1 h^?1) was estimated. Characteristics of the measured NH₃ plume were compared to those predicted by a Lagrangian dispersion model. The spatially integrated pattern of NH₃ concentrations predicted and measured agreed but the measured was often more complex than the predicted spatial distribution. The study suggests that the export of NH₃ through advection accounted for about 90% of the emissions from the feedlot, chemical transformation was insignificant, and dry deposition accounted for the remaining 10%.     

Increasing biogas production from sewage sludge anaerobic co-digestion process by adding crude glycerol from biodiesel industry

In an effort to convert waste streams to energy in a green process, glycerol from biodiesel manufacturing has been used to increase the gas production and methane content of biogas within a mesophilic anaerobic co-digestion process using primary sewage sludge. Glycerol was systematically added to the primary digester from 0% to 60% of the organic loading rate (OLR). The optimum glycerol loading range was from 25% to 60% OLR. This resulted in an 82–280% improvement in specific gas production. Following the feeding schedule described, the digesters remained balanced and healthy until inhibition was achieved at 70% glycerol OLR. This suggests that high glycerol loadings are possible if slow additions are upheld in order to allow the bacterial community to adjust properly. Waste water treatment plant operators with anaerobic digesters can use the data to increase loadings and boost biogas production to enhance energy conversion. This process provides a safe, environmentally friendly method to convert a typical waste stream to an energy stream of biogas.