A preliminary analysis of measurements from a near-field pollutants dispersion campaign in a stratified surface layer

In order to study pollutants dispersion in a stably stratified surface layer at small scales, a pollutants dispersion field experiment programme is being conducted on the site SIRTA in the southern suburb of Paris. In a preliminary campaign held during the winter of 2012 with continuous gas releases, we had 12 ultrasonic anemometers measuring wind velocity and temperature at 10 Hz, and six photo-ionisation detectors measuring gas concentration at 50 Hz. Turbulence is verified to be anisotropic by calculating variances, integral length scales and power spectra of velocity. Some evidence of a -1 power law sub-range has been found in velocity power spectra. Also, we have deduced eddy advection velocity from spatial velocity cross-correlation and found it greater than mean wind speed measured directly by sensors. Concentration measurements are corrected by using a baseline method. Significant relationships between concentration and turbulence measurements at high frequency are still under further study.