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- Title
The Budget of Turbulent Kinetic Energy in the Urban Roughness Sublayer.
- Authors
Christen, Andreas; Rotach, Mathias; Vogt, Roland
- Abstract
Full-scale observations from two urban sites in Basel, Switzerland were analysed to identify the magnitude of different processes that create, relocate, and dissipate turbulent kinetic energy (TKE) in the urban atmosphere. Two towers equipped with a profile of six ultrasonic anemometers each sampled the flow in the urban roughness sublayer, i.e. from street canyon base up to roughly 2.5 times the mean building height. This observational study suggests a conceptual division of the urban roughness sublayer into three layers: (1) the layer above the highest roofs, where local buoyancy production and local shear production of TKE are counterbalanced by local viscous dissipation rate and scaled turbulence statistics are close to to surface-layer values; (2) the layer around mean building height with a distinct inflexional mean wind profile, a strong shear and wake production of TKE, a more efficient turbulent exchange of momentum, and a notable export of TKE by transport processes; (3) the lower street canyon with imported TKE by transport processes and negligible local production. Averaged integral velocity variances vary significantly with height in the urban roughness sublayer and reflect the driving processes that create or relocate TKE at a particular height. The observed profiles of the terms of the TKE budget and the velocity variances show many similarities to observations within and above vegetation canopies.
- Subjects
BASEL (Switzerland); SWITZERLAND; ATMOSPHERIC boundary layer; BUILDING trades education; STOPPING power (Nuclear physics); METEOROLOGICAL instruments; WIND pressure; COST analysis
- Publication
Boundary-Layer Meteorology, 2009, Vol 131, Issue 2, p193
- ISSN
0006-8314
- Publication type
Article
- DOI
10.1007/s10546-009-9359-5