Search Results

You are looking at 1 - 10 of 28 items for

  • Author or Editor: Steven R. Hanna x
  • Refine by Access: Content accessible to me x
Clear All Modify Search
Steven R. Hanna
Full access
Steven R. Hanna

Abstract

Observations of the relative diffusion of 13 sets of tetroon pairs in the mixed layer during convective conditions in eastern Tennessee are reported. The root-mean-square separation S is proportional to time t raised to a power of 1 for times from 2 to 30 min and a power of 0.75 for times from 30 to 100 min. On the average, the observations are satisfied by the approximation dS/dtσ y where σ y is the standard deviation of the lateral wind speed fluctuations, as sensed by the tetroon.

Full access
Steven R. Hanna

Abstract

No abstract available.

Full access
Steven R. Hanna

Abstract

Hourly ground-level concentrations of SF6 at downwind distances ranging from 0.5 to 50 km were observed by the Electric Power Research Institute (EPRI) on dense monitoring networks around power plants at Kincaid, Illinois, and Bull Run, Tennessee. Sigma y on given sampling arcs was estimated by a robust procedure. Over 160 h of data are available from monitoring arcs located at about five downwind distances, which show that σy is close to linear with downwind distance, x. During unstable conditions, σy u/w * x=0.6. When all the data are plotted together, the following empirical equation is valid:

Full access
Steven R. Hanna

Abstract

Full access
Steven R. Hanna
Full access
Steven R. Hanna

Abstract

Extensive meteorological and air chemistry measurements were obtained along the Ventura and Santa Barbara county coastal areas in California during four 2–3 day case studies conducted during the September–October 1985 South-Central Coast Cooperative Aerometric Monitoring Program (SCCCAMP 1985). An overview of the characteristics of ozone episodes during these four case studies is given, showing that the episodes are associated with warm, high pressure systems with light winds. In the absence of easterly winds, the observed ozone in the region is primarily due to local sources. At other times, easterly wind components transport ozone and its precursors from large source regions to the east (i.e., Los Angeles County). This transport sometimes occurs in inland valleys at elevations up to 600 m, and sometimes occurs over the ocean near the surface. Local sea breezes, mesoscale eddies, and terrain-generated winds often cause complex flow patterns and recirculation of pollutants.

Full access
Steven R. Hanna

Abstract

The vertical eddy diffusivity coefficient K is hypothesized to depend upon the parameters that determine the energy spectrum of the vertical velocity fluctuations. Vertical velocity spectra from the lowest 320 m of the atmosphere are used to verify a relation among the rate of dissipation of eddy energy per unit mass, the standard deviation of the vertical velocity fluctuations, and the wavenumber of the peak of the energy spectrum of the vertical velocity fluctuations. Observations at Round Hill, Mass., and Cedar Hill, Tex., are employed to verify that the vertical eddy viscosity KM is proportional to the product of any two of the above parameters. However, the Richardson number must be included with these parameters in order to estimate the vertical eddy conductivity KH. In addition, it is shown that the wavenumber maximum of the vertical velocity spectrum and the nondimensional ratio σ w/u* may be approximated at heights less than 320 m by empirical formulae.

Full access
Steven R. Hanna

Abstract

Formulas for the variation with height of the buoyancy, volume, and water vapor fluxes from large wet cooling towers are derived. The simple formulas developed by Briggs are suggested for estimating plume rise, if the possibility of the release of latent heat is accounted for in the definition of the initial buoyancy flux. The probability of whether condensation will occur is sensitive to small variations in moisture content and temperature of the environment. Verification of the theory is hampered by the scarcity of adequate measurements of cooling tower plumes.

Full access
Steven R. Hanna

Abstract

A one-dimensional plume and cloud growth model is applied to four months of radiosonde observations from Nashville, using as initial conditions the plume from single large cooling towers with waste heat outputs of 103, 104 and 105 MW, and a complex of cooling towers with a total waste heat output of 105 MW. Estimates of average annual plume rise from the four energy sources are 580,1180,2460 and 780 m, respectively.

The predicted plume rise, visible plume length and cloud formation are given as functions of time of day, year and weather type. For example, a cloud forms at the top of the plume from the 103 MW tower in 65% of the morning soundings during which ground level fog was observed. A cloud is predicted to occur 95% of the time at the top of the plume from the single 105 MW tower. It is found that if the towers in an energy center are separated by a distance greater than the average plume rise from one tower, then plume merging is minimized. Observations from TVA's Paradise steam plant are used to test the predictions of visible plume length from a single 103 MW tower.

Full access