189 research outputs found
05/18/1993 - Eastern\u27s 1993 All Student Show Winner Laura Brahos.pdf
This paper reports on the stages forming a model evaluation protocol for urban flow and dispersion models proposed within the COST Action 732 on "Quality Assurance and Improvement of Micro-Scale Meteorological Models". It discusses the different components forming model evaluation with emphasis on validation and implementation of the protocol for the test case Mock Urban Setting Test (MUST). The protocol was proposed with building-resolving models in mind, but integral models have also been included. The suggested approach can be used for further micro-scale model evaluation and for the standardisation of their applications
Analysis of the impact of inhomogeneous emissions in the Operational Street Pollution Model (OSPM)
Semi-parameterized street canyon models, as e.g. the Operational Street
Pollution Model (OSPM<sup>®</sup>), have been
frequently applied for the last two decades to analyse levels and
consequences of air pollution in streets. These models are popular due to
their speed and low input requirements. One often-used simplification is the
assumption that emissions are homogeneously distributed in the entire length
and width of the street canyon. It is thus the aim of the present study to
analyse the impact of this assumption by implementing an inhomogeneous
emission geometry scheme in OSPM. The homogeneous and the inhomogeneous
emission geometry schemes are validated against two real-world cases:
Hornsgatan, Stockholm, a sloping street canyon; and Jagtvej, Copenhagen;
where the morning rush hour has more traffic on one lane compared to the
other. The two cases are supplemented with a theoretical calculation of the
impact of street aspect (height / width) ratio and emission inhomogeneity
on the concentrations resulting from inhomogeneous emissions. The results
show an improved performance for the inhomogeneous emission geometry over the
homogeneous emission geometry. Moreover, it is shown that the impact of
inhomogeneous emissions is largest for near-parallel wind directions and for
high aspect ratio canyons. The results from the real-world cases are however
confounded by challenges estimating the emissions accurately
THE MUST MODEL EVALUATION EXERCISE: STATISTICAL ANALYSIS OF MODELLING RESULTS
The first validation exercise of the COST action 732 lead to a substantial number of simulation results for comparison
with the MUST wind tunnel experiments. Validation metrics for selected simulation results of the flow field and the concentrations
are presented and compared to the state of the art. In addition mean metrics and corresponding scatter limits are computed from the
individual results
THE MUST MODEL EVALUATION EXERCISE: PATTERNS IN MODEL PERFORMANCE
As part of the COST 732 action more than a dozen different research groups have modelled the MUST experiment, as
simulated in a wind tunnel. The model evaluation guidance developed within COST 732 recommends \u27exploratory data analysis\u27 as
one of the elements in model validation. Experience has shown that such exploratory analysis is crucial to reveal shortcomings of
models that might otherwise pass unnoticed. Conditions are best for detecting common patterns and anomalies if you have a
situation where several models are put into a common framework – like the case at hand. The available material provides a unique
opportunity to identify and explore patterns within model performance
Boundary-layer turbulence as a kangaroo process
A nonlocal mixing-length theory of turbulence transport by finite size eddies is developed by means of a novel evaluation of the Reynolds stress. The analysis involves the contruct of a sample path space and a stochastic closure hypothesis. The simplifying property of exhange (strong eddies) is satisfied by an analytical sampling rate model. A nonlinear scaling relation maps the path space onto the semi-infinite boundary layer. The underlying near-wall behavior of fluctuating velocities perfectly agrees with recent direct numerical simulations. The resulting integro-differential equation for the mixing of scalar densities represents fully developed boundary-layer turbulence as a nondiffusive (Kubo-Anderson or kangaroo) type of stochastic process. The model involves a scaling exponent (with → in the diffusion limit). For the (partly analytical) solution for the mean velocity profile, excellent agreement with the experimental data yields 0.58. © 1995 The American Physical Society
Road Traffic Noise and Incident Myocardial Infarction: A Prospective Cohort Study
BACKGROUND Both road traffic noise and ambient air pollution have been associated with risk for ischemic heart disease, but only few inconsistent studies include both exposures. METHODS In a population-based cohort of 57 053 people aged 50 to 64 years at enrolment in 1993-1997, we identified 1600 cases of first-ever MI between enrolment and 2006. The mean follow-up time was 9.8 years. Exposure to road traffic noise and air pollution from 1988 to 2006 was estimated for all cohort members from residential address history. Associations between exposure to road traffic noise and incident MI were analysed in a Cox regression model with adjustment for air pollution (NO(x)) and other potential confounders: age, sex, education, lifestyle confounders, railway and airport noise. RESULTS We found that residential exposure to road traffic noise (L(den)) was significantly associated with MI, with an incidence rate ratio IRR of 1.12 per 10 dB for both of the two exposure windows: yearly exposure at the time of diagnosis (95% confidence interval (CI): 1.02-1.22) and 5-years time-weighted mean (95% CI: 1.02-1.23) preceding the diagnosis. Visualizing of the results using restricted cubic splines showed a linear dose-response relationship. CONCLUSIONS Exposure to long-term residential road traffic noise was associated with a higher risk for MI, in a dose-dependent manner
- …