Abstract

For astronauts and travelers in aircraft, space weather can quickly increase dose rates resulting from naturally occurring ionizing radiation by more than a 1000-fold. Historically, monitoring of these events has been done primarily by a combination of ground-based and satellite instrumentation. At best, these data sources provide a local (ground-level monitors) or global (satellite) average picture of an event as it evolves. With considerable modeling effort, a better global picture of an event emerges after the event has passed. For aviation users this is inadequate. Real-time local estimates on flight routes are preferred to enable appropriate responses from pilots and air traffic management. Modeling and measurement programs are described, and a new aviation dose index is discussed to provide examples of systems that are in development or that have been recently adopted for addressing problems with the current monitoring, warning, and evaluation methods. Document type: Part of book or chapter of book

Abstract

Historical activities at facilities producing nuclear materials for weapons released radioactivity into the air and water. Past studies in the United States have evaluated the release, atmospheric transport and environmental accumulation of 131I from the nuclear facilities at Hanford in Washington State and the resulting dose to members of the public (Farris et al. 1994). A multi-year dose reconstruction effort (Mokrov et al. 2004) is also being conducted to produce representative dose estimates for members of the public living near Mayak, Russia, from atmospheric releases of 131I at the facilities of the Mayak Production Association. The approach to calculating individual doses to members of the public from historical releases of airborne 131I has the following general steps: • Construct estimates of releases 131I to the air from production facilities. • Model the transport of 131I in the air and subsequent deposition on the ground and vegetation. • Model the accumulation of 131I in soil, water and food products (environmental media). • Calculate the dose for an individual by matching the appropriate lifestyle and consumption data for the individual to the concentrations of 131I in environmental media at their residence location. A number of computer codes were developed to facilitate themore » study of airborne 131I emissions at Hanford. The RATCHET code modeled movement of 131I in the atmosphere (Ramsdell Jr. et al. 1994). The DECARTES code modeled accumulation of 131I in environmental media (Miley et al. 1994). The CIDER computer code estimated annual doses to individuals (Eslinger et al. 1994) using the equations and parameters specific to Hanford (Snyder et al. 1994). Several of the computer codes developed to model 131I releases from Hanford are general enough to be used for other facilities. This document provides user instructions for computer codes calculating doses to members of the public from atmospheric 131I that have two major differences from the Hanford modeling sequence. First, the air transport code HYSPLIT (Draxler et al. 2012) is used instead of the RATCHET code. Second, the new individual dose code CiderF replaces the older CIDER code and five auxiliary codes.« le Document type: Report

Abstract

In the context of the ERAINT project, a number of human-in-the-loop simulations were conducted to study the implications of integrating a remote piloted aircraft system (RPAS) into the managed airspace. For the purpose of this study, the RPAS was assumed to be involved in surveillance missions, flying a large-endurance scan pattern. The area of surveillance was selected such that it crossed an active airway for approaches. Furthermore, the simulations also included situations in which the RPAS was involved in an emergency situation such as lost links and engine failures. From previous work, the results obtained from these simulations showed that the air traffic controllers (ATCs) could successfully manage the required separations for airspace safety assurance. Nevertheless, the number of total commands issued increased, in particular the number of requirements for altitude changes, and especially those destined to commercial aircraft. Given an aircraft's flying altitude impact on performance, one question rapidly arose: Is there an increase in flight costs for airlines as a result of the increased number of ATC commands issued to provide the necessary separation with the RPAS? For this purpose two metrics relating to time and fuel are defined such that they are targeted on quantifying the economic impact for commercial air traffic resulting from the presence of a RPAS. Both metrics are computed from the ADS-B traces of all aircraft in the sector and the results of each simulation are compared with those of a baseline simulation, in which the RPAS is not present. To improve on the comparison between each simulation's results we complement this study with a statistical analysis of the available data samples using paired t-test analyses to determine if the observed differences are statistically significant or simply due to random variability. Peer Reviewed

Abstract

Weather conditions are widely acknowledged to contribute to the occurrence of congestion on motorway traffic by influencing both traffic supply and traffic demand. To the best of our knowledge, this is the first paper that explicitly integrates supply and demand effects in predicting the influence of adverse weather conditions on the probability of occurrence of congestion. Traffic demand is examined by conducting a stated adaptation experiment, in which changes in travel choices are observed under adverse weather scenarios. Based on these choices, a Panel Mixed Logit model is estimated. Supply effects are taken into account by examining the influence of precipitation on motorway capacity. Based on the Product Limit Method, capacity distribution functions are estimated for dry weather, light rain and heavy rain. With the developed model to integrate the supply and demand effects breakdown probabilities can be calculated for any given traffic demand and capacity. The results show that rainfall leads to a significant increase in the probability of traffic breakdown at bottleneck locations. Interestingly the probability of a breakdown at these bottleneck locations is predicted to be slightly higher in light rain (98.7%) than in heavy rain (95.7%) conditions, which is the result of the higher traffic demand in light rain conditions. Based on the results presented in this paper, it can be recommended to always incorporate both supply and demand effects in the predictions of motorway breakdown probabilities due to adverse weather conditions to improve the validity of the predictions. © 2015 Editorial Board EJTIR. All rights reserved.

Abstract

The formation and radiative properties of clouds are poorly parameterized in numerical climate models, especially marine boundary layer clouds. Twomey (1991), after describing the importance of cloud microphysics to the climate problem, states Clearly, many more field measurements and laboratory experiments are called for, rather than endless repetitions of computer simulations that are closely related to each other and parameterize in very similar ways.'' The effort described here is a field experimental effort supported by the Department of Energy under its Quantitative Links'' program. The project is called Ship-Trail Evolution Above High Updraft Naval Targets (SEAHUNT). The purpose of this study is to improve our understanding of the meteorological context in which ship trails and other perturbations to marine boundary layer clouds occur. 8 refs., 6 figs. USDOE; USDOE, Washington, DC (United States)