Urban boundary layer profiling using ground-based lidars in Rotterdam City Centre

National meteorological services traditionally deploy their weather stations in rural environments. However, in densely populated country like the Netherlands, weather and air quality in cities is becoming more and more relevant. In order to understand processes influencing the weather and climate in urban areas, measuring vertical profiles in and above the urban canopy layer is critical, especially for verifying weather models. Here, ground-based remote sensing offers the possibility to obtain these profiles.

During the summer of 2022 the Ruisdael Urban-Atmosphere Interactions Intensive Trace-gas and Aerosol Measurement Campaign took place to measure urban emissions of greenhouse gases and air pollution in the Rotterdam area, organized by the Ruisdael Observatory [1]. As part of this campaign a short-range vertical profiling Doppler wind lidar (Vaisala Windcube v2) and an automatic lidar ceilometer (Lufft CHM15K) were installed in the Rotterdam City Centre (Westersingel 12) for three weeks.

The Doppler wind lidar measures horizontal and vertical wind between 40m and 240m, with a vertical resolution of 20m and a sampling time of 4s. Therefore it provides wind and turbulence profiles in and above the urban canopy. They can be compared with nearby rural (Cabauw) and offshore (platforms EPL and LEG) wind profiles. The ceilometer provides cloud base heights and reveals the boundary layer height, relevant for the turbulence profiles. A transect of ceilometers through the Rotterdam area was created by placing an additional ceilometer at the coastline (De Slufter), together with those at Rotterdam The Hague Airport and Cabauw that are part of KNMI's ceilometer network which provides vertically resolved cloud and aerosol data on a national scale.

With these measurements we hope to quantify the influence of buildings in Rotterdam on turbulence and wind profiles, to be used for process-based verification of our numerical weather predication models.

[1] https://ruisdael-observatory.nl/