An investigation of instantaneous diffusion and concentration fluctuations

Journal Article · Fri Dec 01 04:00:00 EST 1995 · Journal of Applied Meteorology

DOI:https://doi.org/10.1175/1520-0450(1995)034<2724:AIOIDA>2.0.CO;2· OSTI ID:274050

Peterson, H ^[1]; Lamb, B ^[2]

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1. Montana Tech of the Univ. of Montana, Butte, MT (United States)
2. Washington State Univ., Pullman, WA (United States)

Instantaneous plume behavior is investigated via experimental and modeling results from a recent field campaign. The data consist of wind velocity and concentration measurements collected 700 m from a point source of sulfur hexafluoride during stable and neutral conditions. Fixed-point and traverse concentration data are analyzed in terms of concentration fluctuation statistics and diffusion coefficients. For the fixed-point data during this study, concentration fluctuation intensities vary between 0.7 and 4.5, intermittency factors are between 0.18 and 0.95, and peak-to-mean ratios range from 4.5 to 41.1. For traverse data, two methods are used to estimate the instantaneous diffusion coefficient {sigma}{sub YI}, which is defined as the standard deviation of the crosswind concentration distribution of the instantaneous plume. Using the moment method, coefficients for this dataset range from 10.3 to 132.1 m. Using the peak concentrations and an assumption of a Gaussian concentration distribution in the vertical and horizontal directions, coefficients are between 6.7 and 22.4 m. The instantaneous diffusion coefficients derived from measured peak concentrations are shown to be less sensitive to plume meander than values calculated from the moment method. The values are related to simple meteorological parameters with three empirical equations, and all three equations predict diffusion coefficients within a few meters of the measured values. When used in a meandering plume model, the diffusion coefficients provide a way to estimate plume concentration fluctuation statistics from simple measurements of the wind. Overall, the model predictions are within a factor of 2 or better for the concentration mean, intensity, intermittency factor, and peak-to-mean ratio under stable through neutral conditions in the absence of large horizontal wind meander. 21 refs., 14 figs., 10 tabs.

• OSTI ID: 274050
• Journal Information: Journal of Applied Meteorology, Journal Name: Journal of Applied Meteorology Journal Issue: 12 Vol. 34; ISSN JOAMEZ; ISSN 0894-8763
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
AIR POLLUTION
CONCENTRATION RATIO
DATA ANALYSIS
DIFFUSION
FLOW MODELS
PLUMES
REAL TIME SYSTEMS
SULFUR FLUORIDES