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Abstract
Micrometeorological measurements made during Project Prairie Grass have been used in an examination of a theoretical model proposed by Swinbank to describe wind speed profiles in the lower portion of the atmospheric boundary layer during conditions of non-neutral temperature stratification. In the derivation of the Swinbank hypothesis the Monin-Obukhov length, L, is employed. The derivation depends upon an assumption that L is constant in the lower boundary layer. The analysis of the observational data, however, reveals a systematic increase of 1/L with height during lapse conditions and a systematic decrease of 1/L with height during inversion conditions. Unsuccessful attempts to explain these variations of 1/L with height are discussed. It is concluded that the Swinbank hypothesis is not verified by the micrometeorological data of Project Prairie Grass.
Abstract
Micrometeorological measurements made during Project Prairie Grass have been used in an examination of a theoretical model proposed by Swinbank to describe wind speed profiles in the lower portion of the atmospheric boundary layer during conditions of non-neutral temperature stratification. In the derivation of the Swinbank hypothesis the Monin-Obukhov length, L, is employed. The derivation depends upon an assumption that L is constant in the lower boundary layer. The analysis of the observational data, however, reveals a systematic increase of 1/L with height during lapse conditions and a systematic decrease of 1/L with height during inversion conditions. Unsuccessful attempts to explain these variations of 1/L with height are discussed. It is concluded that the Swinbank hypothesis is not verified by the micrometeorological data of Project Prairie Grass.
Abstract
The 1428-lt television transmitter tower, located at Cedar Hill, Texas, and instrumented to obtain continuous measurements of wind and temperature at 12 levels from 30 ft to 1420 ft above ground, is proving to be a useful research tool for investigating low-level meteorological phenomena, especially the low-level jet. During the night of 22–23 February 1961, a pronounced low-level jet was recorded. Systematic variations of wind speed and temperature with time and height will be discussed to illustrate the orderly development of the low-level jet, the upward growth of the nocturnal inversion, and the vertical extent of the mixing process within the deepening inversion.
Abstract
The 1428-lt television transmitter tower, located at Cedar Hill, Texas, and instrumented to obtain continuous measurements of wind and temperature at 12 levels from 30 ft to 1420 ft above ground, is proving to be a useful research tool for investigating low-level meteorological phenomena, especially the low-level jet. During the night of 22–23 February 1961, a pronounced low-level jet was recorded. Systematic variations of wind speed and temperature with time and height will be discussed to illustrate the orderly development of the low-level jet, the upward growth of the nocturnal inversion, and the vertical extent of the mixing process within the deepening inversion.
Abstract
In the Green Glow program conducted near Richland, Washington, during the summer of 1959, 26 diffusion experiments were conducted during nocturnal inversions. The tracer was released near ground level. Samplers were placed at 1.5 m above ground at 533 positions on six sampling arcs, the radii of which were 200 m, 800 m, 1.6 km, 3.2 km, 12.8 km, and 25.6 km. In addition to the ground sampling network, poles or towers were erected at five points, 8 deg apart, on each of the four inner arcs. Fifteen samplers were mounted on each pole or tower, the top level increasing from 27 m on the 200 m arc to 62 m on the 1.6 km and 3.2 km arcs.
The vertical measurements of tracer dosage made during Experiment No. 3 suggest that during this experiment, conducted during one of the stronger inversions, the mean wind direction changed significantly with height in the lowest 200 ft. Direct measurements of mean wind direction confirm this notion.
A diffusion model is discussed in which the tracer dosage at a point downwind from the source is given by the normal frequency function of two variables (the lateral and vertical coordinates of the point) and the correlation coefficient between the lateral and vertical coordinates of the tracer particles. Experiment No. 3 is examined in terms of this model and is found to satisfy well the major conditions of the model. In addition, the model and the empirical evidence suggest that care must be exercised in the interpretation of computations of diffusion parameters made from photographs of visible tracers.
Abstract
In the Green Glow program conducted near Richland, Washington, during the summer of 1959, 26 diffusion experiments were conducted during nocturnal inversions. The tracer was released near ground level. Samplers were placed at 1.5 m above ground at 533 positions on six sampling arcs, the radii of which were 200 m, 800 m, 1.6 km, 3.2 km, 12.8 km, and 25.6 km. In addition to the ground sampling network, poles or towers were erected at five points, 8 deg apart, on each of the four inner arcs. Fifteen samplers were mounted on each pole or tower, the top level increasing from 27 m on the 200 m arc to 62 m on the 1.6 km and 3.2 km arcs.
The vertical measurements of tracer dosage made during Experiment No. 3 suggest that during this experiment, conducted during one of the stronger inversions, the mean wind direction changed significantly with height in the lowest 200 ft. Direct measurements of mean wind direction confirm this notion.
A diffusion model is discussed in which the tracer dosage at a point downwind from the source is given by the normal frequency function of two variables (the lateral and vertical coordinates of the point) and the correlation coefficient between the lateral and vertical coordinates of the tracer particles. Experiment No. 3 is examined in terms of this model and is found to satisfy well the major conditions of the model. In addition, the model and the empirical evidence suggest that care must be exercised in the interpretation of computations of diffusion parameters made from photographs of visible tracers.
Abstract
Wind tunnel and field experiments have shown that the fast-response three-component sonic anemometer is a highly accurate wind speed sensor. When sonic anemometers were used as reference sensors for wind speed, slower response cup anemometers were found to consistently overestimate the wind speed. Despite measures taken during a field program in Kansas to minimize tower influence on wind measurements, the errors due to the tower effect on the windward side are inferred to be about ±5% of the observed wind speed ratios of cup to sonic anemometers. When the observed speed ratios are compared with the errors due to tower influence, the overspeeding of the cup anemometer is estimated to be about 10% of the reference wind speed.
Abstract
Wind tunnel and field experiments have shown that the fast-response three-component sonic anemometer is a highly accurate wind speed sensor. When sonic anemometers were used as reference sensors for wind speed, slower response cup anemometers were found to consistently overestimate the wind speed. Despite measures taken during a field program in Kansas to minimize tower influence on wind measurements, the errors due to the tower effect on the windward side are inferred to be about ±5% of the observed wind speed ratios of cup to sonic anemometers. When the observed speed ratios are compared with the errors due to tower influence, the overspeeding of the cup anemometer is estimated to be about 10% of the reference wind speed.
Abstract
Sutton's hypothesis for diffusion from a continuous point source has been evaluated using the data obtained during Project Prairie Grass. It is found that the hypothesis predicts the observed concentration distributions only if there are two values of Sutton's “n”, one to characterize lateral diffusion (n y ) and one to characterize vertical diffusion (n z ). Statistical tests indicate that n y and n z are invariant with distance between 100 and 800 m of the source, but that the values of n y and n z appropriate for these distances exceed the values within 100 m of the source. It is also shown that neither n y nor n z can be specified by nw1 , the value of n found from a power-law fit to the wind profile in the lowest 8 meters.
Abstract
Sutton's hypothesis for diffusion from a continuous point source has been evaluated using the data obtained during Project Prairie Grass. It is found that the hypothesis predicts the observed concentration distributions only if there are two values of Sutton's “n”, one to characterize lateral diffusion (n y ) and one to characterize vertical diffusion (n z ). Statistical tests indicate that n y and n z are invariant with distance between 100 and 800 m of the source, but that the values of n y and n z appropriate for these distances exceed the values within 100 m of the source. It is also shown that neither n y nor n z can be specified by nw1 , the value of n found from a power-law fit to the wind profile in the lowest 8 meters.
Abstract
Statistical summaries are presented of computed values of parameters appearing in a modification of Sutton's diffusion equations. Experimental data used for the computations are those obtained during Project Prairie Grass at O'Neill, Nebraska and those obtained at Round Hill, Massachusetts. Stratification of the parameters n y and n z according to stability class reveals systematic variations of class-median values of ny and nz with stability class and a large range of ny and nz within any given stability class. No difference in the results was found between the two sets of experiments for these parameters.
The parameter, C y , has a mean value of about 0.4 for the Prairie Grass experiments and about 0.9 for the Round Hill experiments. No relationship between C y and stability was found for the Prairie Grass experiments, but a correlation coefficient of 0.22 between C y and stability ratio was found for the Round Hill experiments.
The parameter, C z , computed only for the Prairie Grass experiments, has a mean value of about 0.07 and is independent of stability for those experiments permitting a statistically-stable estimate of C z .
Abstract
Statistical summaries are presented of computed values of parameters appearing in a modification of Sutton's diffusion equations. Experimental data used for the computations are those obtained during Project Prairie Grass at O'Neill, Nebraska and those obtained at Round Hill, Massachusetts. Stratification of the parameters n y and n z according to stability class reveals systematic variations of class-median values of ny and nz with stability class and a large range of ny and nz within any given stability class. No difference in the results was found between the two sets of experiments for these parameters.
The parameter, C y , has a mean value of about 0.4 for the Prairie Grass experiments and about 0.9 for the Round Hill experiments. No relationship between C y and stability was found for the Prairie Grass experiments, but a correlation coefficient of 0.22 between C y and stability ratio was found for the Round Hill experiments.
The parameter, C z , computed only for the Prairie Grass experiments, has a mean value of about 0.07 and is independent of stability for those experiments permitting a statistically-stable estimate of C z .
Abstract
During the summer of 1959, the Green Glow program, consisting of 26 diffusion experiments during nocturnal inversions, was conducted at the Atomic Energy Commission's Hanford Site near Richland, Wash. The tracer, zinc sulfide, was released near ground level. Samplers were placed at 1.5 m above ground at 533 positions on six sampling arcs, the radii of which were 200 m, 800 m, 1.6 km, 3.2 km, 12.8 km, and 25.6 km. In addition to the ground sampling network, poles or towers were erected at 5 points, 8 deg apart, on each of the 4 inner arcs. Fifteen samplers were mounted on each pole or tower, the top level increasing from 27 m on the 200-m arc to 62 m on the 1.6-km and 3.2-km arcs.
General aspects of the experimental design and tracer technique are discussed along with terrain characteristics and meteorological conditions pertinent to these experiments. Experimental results are presented showing the increase in horizontal plume width and decrease of maximum exposure with distance from the source. An analysis of the area enclosed within a given exposure isopleth is summarized. The effect of significant wind direction shear on the vertical distributions of exposure is discussed. Results from the Green Glow experiments are compared with those from earlier diffusion experiments at O'Neil, Nebr., and later experiments at Hanford.
Abstract
During the summer of 1959, the Green Glow program, consisting of 26 diffusion experiments during nocturnal inversions, was conducted at the Atomic Energy Commission's Hanford Site near Richland, Wash. The tracer, zinc sulfide, was released near ground level. Samplers were placed at 1.5 m above ground at 533 positions on six sampling arcs, the radii of which were 200 m, 800 m, 1.6 km, 3.2 km, 12.8 km, and 25.6 km. In addition to the ground sampling network, poles or towers were erected at 5 points, 8 deg apart, on each of the 4 inner arcs. Fifteen samplers were mounted on each pole or tower, the top level increasing from 27 m on the 200-m arc to 62 m on the 1.6-km and 3.2-km arcs.
General aspects of the experimental design and tracer technique are discussed along with terrain characteristics and meteorological conditions pertinent to these experiments. Experimental results are presented showing the increase in horizontal plume width and decrease of maximum exposure with distance from the source. An analysis of the area enclosed within a given exposure isopleth is summarized. The effect of significant wind direction shear on the vertical distributions of exposure is discussed. Results from the Green Glow experiments are compared with those from earlier diffusion experiments at O'Neil, Nebr., and later experiments at Hanford.
