Journal Article

Evaluation of Urban Local-Scale Aerodynamic Parameters: Implications for the Vertical Profile of Wind Speed and for Source Areas

Grimmond, Sue, Barlow, Janet, Kent, Christoph W., Halios, Christos H., Lindberg, Fredrik, Gatey, David, Kotthaus, Simone

2017

Overview

Nine methods to determine local-scale aerodynamic roughness length ( z 0 ) and zero-plane displacement ( z d ) are compared at three sites (within 60 m of each other) in London, UK. Methods include three anemometric (single-level high frequency observations), six morphometric (surface geometry) and one reference-based approach (look-up tables). A footprint model is used with the morphometric methods in an iterative procedure. The results are insensitive to the initial z d and z 0 estimates. Across the three sites, z d varies between 5 and 45 m depending upon the method used. Morphometric methods that incorporate roughness-element height variability agree better with anemometric methods, indicating z d is consistently greater than the local mean building height. Depending upon method and wind direction, z 0 varies between 0.1 and 5 m with morphometric z 0 consistently being 2–3 m larger than the anemometric z 0 . No morphometric method consistently resembles the anemometric methods. Wind-speed profiles observed with Doppler lidar provide additional data with which to assess the methods. Locally determined roughness parameters are used to extrapolate wind-speed profiles to a height roughly 200 m above the canopy. Wind-speed profiles extrapolated based on morphometric methods that account for roughness-element height variability are most similar to observations. The extent of the modelled source area for measurements varies by up to a factor of three, depending upon the morphometric method used to determine z d and z 0 .

• Publisher: Springer Netherlands,Springer,Springer Nature B.V
• Subject: Aerodynamic roughness length / Aerodynamics / Anemometric methods / Atmospheric boundary layer / Atmospheric Protection/Air Quality Control/Air Pollution / Atmospheric Sciences / Canopy / Displacement / Doppler lidar / Doppler sonar / Earth and Environmental Science / Earth Sciences / Evaluation / Formulae / geometry / Height / High frequency / Length / Lidar / Logarithmic wind-speed profile / Lookup tables / Meteorologi och atmosfärsvetenskap / Meteorology / Meteorology and Atmospheric Sciences / Morphometric methods / Morphometry / Naturgeografi / Parameters / Physical Geography / Profiles / Research Article / Roughness / Roughness length / Roughness parameters / Source area / Surface geometry / Tables / United Kingdom / Urban areas / Variability / Velocity measurement / Vertical profiles / Wind direction / Wind speed / Zero-plane displacement