Evaluating modelled winds over an urban area using ground‐based Doppler lidar observations

Abstract

Wind information in urban areas is essential for many applications related to air pollution, urban climate and planning, safety of drone-related operations, and assessment of urban wind energy potential. These applications require accurate wind forecasts, and obtaining this information in an urban environment is challenging as the morphology of a city varies from street to street, altering the wind flow. Remote sensing techniques such as Doppler lidars (light detection and ranging) provide a unique opportunity for wind forecast verification as they can provide both the vertical profile of the horizontal wind and the spatial variation in the horizontal domain at high resolution. In this study, the performance of numerical weather prediction (NWP) models, analysis systems, and large-eddy simulation (LES) models have been analysed by comparing the modelled winds against Doppler lidar observations under various atmospheric conditions and from season to season, in the coastal environment of Helsinki, Finland. The long-term mean vertical profile of the modelled horizontal wind shows good agreement with observations; the NWP model and the analysis systems selected here exhibit different strengths and weaknesses depending on the atmospheric conditions but no significant diurnal variation in performance. However, both the model and analysis systems show differences in their spatially-averaged bias when investigating different wind directions. LES verification shows that these models can potentially provide winds down to Associated post doc with Vaisala through PoDoCo program.

Influences of lidar scanning parameters on wind turbine wake retrievals in complex terrain

“…We recommend scanning configurations that increase the density of retrieval points over the wake by reducing the spacing between range gates and placement or angular resolution to reduce the distance between beams; the performance of DLR1 compared to DLR2 evidences some of the potential benefits. Beyond characterizing heterogeneous flows like wind turbines wakes, lidars are also used for assessing heterogeneous flows in urban areas (Newsom et al, 2008;Filioglou et al, 2022), land-water transitions, and internal boundary layers (Krishnamurthy et al, 2023). This virtual lidar tool can help enable quantification of possible errors due to scanning geometries and scanning strategies, to enable optimal field experiment planning and instrument deployment.…”

Editorial: Atmospheric processes and applications in urban, coastal and mountainous terrain

“…In this Special Issue, the connection between thermal stratification, vertical wind shear and air pollutant concentrations is evaluated by Kiseleva et al (2021) for the city of Stuttgart (Germany), located in moderate mountainous terrain, considering in particular NO x and O 3 concentrations as a function of the bulk Richardson number. Filioglou et al (2022) focus on the ability of numerical weather prediction models, analysis systems and large‐eddy simulations (LES) to reproduce the wind field in the coastal city of Helsinki (Finland), highlighting that LES can potentially resolve the wind field in the urban canopy layer, given pre‐computed scenarios of atmospheric conditions.…”

Observations of Tall-Building Wakes Using a Scanning Doppler Lidar

“…However, remote sensing methods are well-suited to profiling urban boundary layers (Barlow et al, 2011a;Kotthaus et al, 2022). Doppler lidars have been used to measure boundary layer depth and turbulence profiles (Barlow et al, 2015;Kongara et al, 2012) under different atmospheric stabilities and analyse the response of the urban wind profile to surface roughness (Drew et al, 2013;Kikumoto et al, 2017;Ortiz-Amezcua et al, 2022;Filioglou et al, 2022). Dual Doppler lidars have potential for improving pollution dispersion models (Collier et al, 2005) due to more accurate retrieval of the wind field in highly turbulent urban flows.…”