Numerical modelling of mesoscale atmospheric dispersion. (Volumes I and II)

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:7266020

Moran, M D

Mesoscale atmospheric dispersion is more complicated than smaller-scale dispersion because the mean wind field can no longer be considered steady or horizontally homogeneous over mesoscale time and space scales. Wind shear also plays an important role on the mesoscale, and horizontal dispersion can be enhanced and even dominated by vertical wind shear through either the simultaneous or delayed interaction of horizontal differential advection and vertical mixing. The CSU mesoscale atmospheric dispersion modelling system has been used in this study to simulate the transport and diffusion of a perfluorocarbon gas for episodic releases made during two mesoscale dispersion field experiments. The physiography of the two experimental domains was quite different, permitting isolation and examination of the roles of terrain forcing and differential advection in mesoscale atmospheric dispersion. Suites of numerical experiments of increasing complexity were carried out for both case studies. The experiments differed in the realism of their representation of both the synoptic-scale flow and the underlying terrain. The contributions of differential advection and mesoscale deformation to mesoscale dispersion dominated those of small-scale turbulent diffusion for both cases, and Pasquill's (1962) delayed-shear-enhancement mechanism for lateral dispersion was found to be particularly important. This study was also the first quantitative evaluation of the CSU mesoscale dispersion modelling system with episodic mesoscale dispersion field data. The modelling system showed considerable skill in predicting quantitative tracer-cloud characteristics such as peak concentration, maximum cloud width, arrival time, transit time, and crosswind integrated exposure. Model predictions also compared favorably with predictions made by a number of other mesoscale dispersion models for the same two case studies.

• Research Organization: Colorado State Univ., Fort Collins, CO (United States)
• OSTI ID: 7266020
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
EARTH ATMOSPHERE
ENVIRONMENTAL TRANSPORT
ORGANIC FLUORINE COMPOUNDS
ATMOSPHERIC CIRCULATION
AIR POLLUTION MONITORING
DISPERSIONS
METEOROLOGY
STATISTICAL MODELS
USA
WIND
DEVELOPED COUNTRIES
MASS TRANSFER
MATHEMATICAL MODELS
MONITORING
NORTH AMERICA
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
540120* - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)