Meteorological Influences on Smoke/Obscurant Effectiveness. Phase 2. Volume 2
Final rept. Aug 1989-Nov 1991,
SIGMA RESEARCH CORP WESTFORD MA
Pagination or Media Count:
A field experiment was carried out in which wind speed and direction were measured over flat terrain at a height of 10 m using 13 identical instruments spaced logarithmically along two perpendicular 10 km lines. Station separations ranged from 312 m to 1000 m. One-minute data from 11 sampling periods of duration 6 to 10 hours were studied. The statistics showed little dependence on whether the line of instruments was oriented along the wind or across the wind, or whether wind speeds or wind directions were being analyzed. The integral time scale derived from the variation of the single station variances with averaging time was found to equal several minutes. The correlation coefficients between two stations separated by distance the change in x were found to vary exponentially with the change in x, with an integral distance scale on the order of 1 km. At a station separation of 10 km, the correlation coefficient equals 0.24, 0.37, and 0.47 for averaging times of 1, 10, and 60 minutes respectively. These correlation coefficients correspond to root-mean-square differences in wind speed at the two stations of about 1.2, 1.1, and 1.0 ms respectively.