PROJECT PRAIRIE GRASS
WHEN: July and August, 1956 (10-min sampling of tracer)
LOCATION: The experimental site was approximately five miles northeast of O’Neil, Nebraska. 42.49333 degrees North Latitude and 98.571666 degrees West Longitude. <PGrassVol1Chap2.pdf(225KB)>
TRACER: Sulfur Dioxide, SO2.
RELEASE: Plastic pipe two-inches in diameter with a small right-angle bend at the top to provide a horizontal release. The height of the release was 0.46m for all experiments, except experiments 63-68 where it was adjusted to be 1.5m above ground. <PGrassVol1Chap5.pdf(4.3MB)>
SAMPLING:
Horizontal sampling array: Five arcs (50, 100, 200, 400, 800m) downwind of the release. All sampled over a 180 degree arc centered on the release at a height of 1.5m. The receptor spacing was every two-degrees on the inner four arcs, and every one-degree on the outer 800m arc. Sampling was along a semicircle from west (270 degrees) to north to east (90 degrees), with the release due south of the north point of the sampling array. <PGrassVol1Chap5.pdf(4.3MB)>
Vertical sampling array: Six lightweight metal towers positioned along the 100m arc, provided samples at nine heights (0.5, 1.0, 1.5, 2.5, 4.5, 7.5, 10.5, 13.5, and 17.5m). The towers were spaced at 14 degree intervals along the 100m arc at the following positions: 325, 339, 353, 7, 21 and 35 degrees. <PGrassVol1Chap5.pdf(4.3MB)>
METEOROLOGY:
On-Site Meteorology:
1. Slow-response observations. For the duration of the field experiments, mean horizontal wind direction and wind speed, and wind direction frequency (taken at 2.5s intervals) were collected at two locations: a) 25m west of the release location, and b) 450m downwind of the release and 30m west of the centerline of the receptor array. At both locations the instruments were at 2m above ground. Results were tabulated for a 10-min and a 20-min period. The 20-min period begins 5-min prior to 10-min tracer sampling period. At the release location, the 10-min meteorological data coincides with the tracer sampling period. At the 450m location, the 10-min meteorological data starts 450m/V seconds later than the start of the tracer sampling period, where V is the 10-min average wind speed, in m/s, at the release point. Note, when V is less than or equal to 1.5 m/s, the last 10-min of the 20-min sampling period was used to develop the 10-min meteorological results for the 450m location. <PGrassVol1Chap6.pdf(2.3MB)>
2. Micrometeorological observations. For 70 tracer data collection periods, air temperature and vapor pressure (8 heights), wind speed (7 heights), soil temperature (6 depths) were collected. Results were tabulated for the 10-min tracer sampling period and for a 20-min period that began 5-min prior to the beginning of the tracer sampling period. The tower location for these data was just beyond the 800m sampling arc. <PGrassVol2Chap8.pdf(345KB)>
3. Rawinsonde observations. A rawinsonde ascent was made at the test site for all gas releases except those numbered 35s and 48s. <PGrassVol2Chap12.pdf(416KB)>
Surface weather observations:
Surface weather observations were recorded for each of the gas release periods. <PGrassVol1Chap3.pdf(90KB)>
DIGITAL DATA FILES:
Tracer Observations
1. Emission release rate. <PGrassTable5_1.xls(15KB)>
2. Horizontal sampling array concentration values (380KB). See Table 2.1 (16KB) of User’s Guide for D6589 for format of data file.
3. Vertical sampling array concentration values. I have entered the values into an Excel spreadsheet. The print on some of the pages was faded, so if you see corrections, please let me know, so I can make corrections. I have also listed the values in a txt file, for use and visual inspection. <PGTable5.3.xls ( 57KB)> <PGVertConc.txt (46KB)>
4. Correction factors for evaporative loss. The temperatures were warm enough that evaporation occurred prior to analysis of the sample concentration values. This means the reported concentration values (listed in the tables) are slightly higher than they should be, 3 to 5 percent for the nighttime experiments and 6 to 9 percent for the daytime experiments. The digitized concentration values reported at this web site are exactly as listed in the data volume, and hence have yet to be corrected for evaporative loss. <PGrassTable_5_4.txt (4KB)>
Meteorological Observations
1. Slow-response 2m observations <Not digitized>
2. Micrometeorological wind speed and temperature observations <PGrassTTUU.txt (17KB)>
3. Rawinsonde observations <Not digitized>. The data are listed in <PGrassVol2Chap12.pdf(416KB)>
4. Day-time mixing heights. Dr. Gary Briggs (formerly a member of the NOAA Meteorology Division on assignment to the EPA) analyzed the rawinsonde data and computed mixing heights for those releases conducted during daytime hours. <PGrassDaytimeZi.xls(16KB)>
REFERENCES:
Barad, M.L. (Editor) (1958): Project Prairie Grass, A Field Program In Diffusion. Geophysical Research Paper, No. 59, Vol I , Report AFCRC-TR-58-235(I), Air Force Cambridge Research Center, 299 pp. <PGrassVolumeI(15.4MB)>
Barad, M.L. (Editor) (1958): Project Prairie Grass, A Field Program In Diffusion. Geophysical Research Paper, No. 59, Vol I I, Report AFCRC-TR-58-235(II), Air Force Cambridge Research Center, 218 pp. <PGrassVolumeII(7.8MB)>
Haugen, D.A. (Editor) (1959): Project Prairie Grass, A Field Program In Diffusion, Geophysical Research Papers, No. 59, Vol III, AFCRC-TR-58-235(III), Air Force Cambridge Research Center, 686 pp. <PGrassVolumeIII(36.1MB)>