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- Author or Editor: M. E. Brooks x
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Abstract
Over 50 cases of TIROS-viewed cloud vortices associated with extratropical cyclones over North America, Europe and Asia between April 1962 and November 1963 were examined to determine what meteorological information could be derived from the satellite pictures. Radiosonde stations were grouped in five principal classes according to their time-adjusted positions with reference to the vortex center and the major cloud bands. Meteorological parameters were statistically related to the age of the vortex, season, and geographical location as Well as to the principal sounding class for the position of the station.
The thermal results indicated that the means of the dew-point depression for each principal class were significantly different from the overall mean of the sample, according to the analysis of variance test. Relative tropopause heights were estimated from the means and variances of the vertical temperature differences. These results will be of value as input parameters for numerical prediction over data-silent areas.
The wind results showed that the wind directions within 333 km ahead of the major cloud band aids averaged 16° clockwise from the nearest band orientation, and behind the bands, 25° clockwise. The mean vertical wind shears within the major cloud bands and in the dry zones behind the bands were about 60° and 20°, respectively, clockwise from the band orientation. Most of the cloud bands were characterized by a speed convergence of the normal components and by a cyclonic shear and vorticity of the parallel components of the mean winds on the two sides of the bands.
Abstract
Over 50 cases of TIROS-viewed cloud vortices associated with extratropical cyclones over North America, Europe and Asia between April 1962 and November 1963 were examined to determine what meteorological information could be derived from the satellite pictures. Radiosonde stations were grouped in five principal classes according to their time-adjusted positions with reference to the vortex center and the major cloud bands. Meteorological parameters were statistically related to the age of the vortex, season, and geographical location as Well as to the principal sounding class for the position of the station.
The thermal results indicated that the means of the dew-point depression for each principal class were significantly different from the overall mean of the sample, according to the analysis of variance test. Relative tropopause heights were estimated from the means and variances of the vertical temperature differences. These results will be of value as input parameters for numerical prediction over data-silent areas.
The wind results showed that the wind directions within 333 km ahead of the major cloud band aids averaged 16° clockwise from the nearest band orientation, and behind the bands, 25° clockwise. The mean vertical wind shears within the major cloud bands and in the dry zones behind the bands were about 60° and 20°, respectively, clockwise from the band orientation. Most of the cloud bands were characterized by a speed convergence of the normal components and by a cyclonic shear and vorticity of the parallel components of the mean winds on the two sides of the bands.
Abstract
The first phase of an atmospheric tracer experiment program, designated Project Sagebrush, was conducted at the Idaho National Laboratory in October 2013. The purpose was to reevaluate the results of classical field experiments in short-range plume dispersion (e.g., Project Prairie Grass) using the newer technologies that are available for measuring both turbulence levels and tracer concentrations. All releases were conducted during the daytime with atmospheric conditions ranging from neutral to unstable. The key finding was that the values of the horizontal plume spread parameter σ y tended to be larger, by up to a factor of ~2, than those measured in many previous field studies. The discrepancies tended to increase with downwind distance. The values of the ratio σ y /σ θ , where σ θ is the standard deviation of the horizontal wind direction, also trend near the upper limit or above the range of values determined in earlier studies. There was also evidence to suggest that the value of σ y began to be independent of σ θ for σ θ greater than 18°. It was also found that the commonly accepted range of values for σ θ in different stability conditions might be limiting, at best, and might possibly be unrealistically low, especially at night in low wind speeds. The results raise questions about the commonly accepted magnitudes of σ y derived from older studies. These values are used in the parameterization and validation of both older stability-class dispersion models as well as newer models that are based on Taylor’s equation and modern PBL theory.
Abstract
The first phase of an atmospheric tracer experiment program, designated Project Sagebrush, was conducted at the Idaho National Laboratory in October 2013. The purpose was to reevaluate the results of classical field experiments in short-range plume dispersion (e.g., Project Prairie Grass) using the newer technologies that are available for measuring both turbulence levels and tracer concentrations. All releases were conducted during the daytime with atmospheric conditions ranging from neutral to unstable. The key finding was that the values of the horizontal plume spread parameter σ y tended to be larger, by up to a factor of ~2, than those measured in many previous field studies. The discrepancies tended to increase with downwind distance. The values of the ratio σ y /σ θ , where σ θ is the standard deviation of the horizontal wind direction, also trend near the upper limit or above the range of values determined in earlier studies. There was also evidence to suggest that the value of σ y began to be independent of σ θ for σ θ greater than 18°. It was also found that the commonly accepted range of values for σ θ in different stability conditions might be limiting, at best, and might possibly be unrealistically low, especially at night in low wind speeds. The results raise questions about the commonly accepted magnitudes of σ y derived from older studies. These values are used in the parameterization and validation of both older stability-class dispersion models as well as newer models that are based on Taylor’s equation and modern PBL theory.
