Modifications of boundary layer wind profiles across the urban area of Paris measured using a transect of six ground-based doppler wind lidars

Doppler wind lidars (DWL) offer high-resolution wind profile measurements valuable for understanding atmospheric boundary layer (ABL) dynamics and provide novel means of studying modifications of airflow over urban areas. Here six ground-based DWL, deployed in a multi-institutional effort along a 40 km transect  through the centre of the metropolitan area of Paris (France), are used to retrieve simultaneous horizontal wind speed and direction through the entire ABL. Data between different DWL systems are harmonized and quality controlled. The DWL dataset is evaluated using in-situ measurements from Eiffel Tower and radiosondes. Based on this unique dataset, we explore for different forcing weather conditions how vertical wind profiles are affected and modified by roughness and thermal effects of a large built-up area. For strong synoptic forcing along the transect, we find generally a near-surface wind reduction over the built-up city centre associated with an anti-clockwise turning of the wind direction and a subsequent acceleration downwind. For clear-sky and weak synoptic conditions more complex wind profiles emerge. This unique, spatially dense, open dataset is providing an assimilation or evaluation dataset for high-resolution weather, climate, inverse and air pollution models that resolve city-scale processes.