ISSN:
1573-1472
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
,
Physics
Notes:
Abstract Many applied dispersion models require the knowledge of boundary-layer parameters such as sensible heat flux,Q H , friction velocity,u *, and turbulent energy components, σw and σ v . Formulas are suggested for calculating these parameters over a wide variety of types of ground surfaces, based on simple observations of wind speed near the ground and fractional cloud cover, and specification of constants such as roughness length, albedo, and soil moisture availability. Observations ofu *,Q H , σ w , and σ v during field experiments in St. Louis and Indianapolis are used to test the formulas for urban sites. Relative errors of about ±20% in the predictions are seen to occur whenu *,Q H , σ w , and σ v are large. However, when these quantities are small (e.g.,u * 〈 0.2 m/s), the errors in the predictions are as large as the mean value of the quantity itself. In addition, it is concluded from studies of available field data and theories that the magnitude of σ w is not well-known at elevations above about 100m during the late afternoon and night. Some simple parameterizations for σ w . are suggested that are consistent with the observed steady decrease in ground-level concentration in the afternoon and the sudden increase in concentration that can occur a few hours after sunset due to wind shears associated with a low-level jet, for continuous plumes emitted from moderate to tall stacks.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02033826
