Citation: Pîrloag˘ a, R.; Adam, M.; Antonescu, B.; Andrei, S.; ¸ Stefan, S. Ground-Based Measurements of Wind and Turbulence at Bucharest–M˘ agurele: First Results. Remote Sens. 2023, 15, 1514. https:// doi.org/10.3390/rs15061514 Academic Editor: Mark Bourassa Received: 8 February 2023 Revised: 6 March 2023 Accepted: 7 March 2023 Published: 9 March 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). remote sensing Article Ground-Based Measurements of Wind and Turbulence at Bucharest–M˘ agurele: First Results R˘ azvan Pîrloag ˘ a 1,2, * ,† , Mariana Adam 1,† , Bogdan Antonescu 2,3 , Simona Andrei 1 and Sabina ¸ Stefan 2 1 Remote Sensing Department, National Institute of Research and Development for Optoelectronics—INOE 2000, Str. Atomi¸ stilor 409, M ˘ agurele, RO077125 Ilfov, Romania 2 Faculty of Physics, University of Bucharest, Str. Atomi¸ stilor 405, M ˘ agurele, RO077125 Ilfov, Romania 3 Future Climate Research, Str. Bl˘ ajel 13, RO031493 Bucharest, Romania * Correspondence: razvan.pirloaga@inoe.ro † These authors contributed equally to this work. Abstract: Doppler wind lidar measurements were used for the first time in Romania to analyse the wind and turbulence statistics for a peri-urban site located at M˘ agurele, southwest of Bucharest. Vertical and scanning measurements between December 2019 and November 2021 were processed using an existing toolbox. The statistics over the two-year period were performed on seasonal and diurnal cycle bases. The analyses showed a diurnal cycle for the horizontal wind speed, with lower values during daytime. In the upper part of the planetary boundary layer (PBL), the wind speed is lowest during the day and highest at night (near surface, the behaviour is reversed). The diurnal cycle has variations during the year (from approximately 500 m during midnight winter to approximately 1250 m during summer noon). The wind direction during autumn shows similarities with the summer season, with prevailing directions from east and northeast. The winter season is characterised by westerly winds. The most variable diurnal wind direction is observed during summer, with nighttime westerly winds and changing directions (from northeast to west) during daytime. The ERA5 reanalysis shows similar patterns for wind speed with Doppler wind lidar (slightly underestimated) and direction. The planetary boundary layer classes over the altitude region analysed shows the predominant convection during daytime and non-turbulent behaviour during nighttime. To a lesser extent, the intermittent turbulent class is observed during the growth and the decay of the mixing layer. Keywords: doppler wind lidar; wind; planetary boundary layer; statistical analysis; turbulence 1. Introduction According to the World Meteorological Organization, several surface variables are essential for understanding Earth’s climate stem: precipitation, pressure, surface radiation budget, temperature, water vapour, and surface wind [1]. Surface wind contributes to, among others, heat and air pollutants transport and is also associated, in the case of extreme wind events, with significant societal and economical impact (e.g., lost of life, damages to infrastructure). Wind is also a key variable for understanding the physical processes in the planetary boundary layer (PBL). Thus, the retrieval of wind speed and direction with high temporal and spatial resolution is of utmost importance. Such wind retrievals can also be used in aviation, meteorology, and the energy sector. High resolution wind data are needed to obtain information regarding on the low-level wind shear and turbulence which are vital information for flight safety, e.g., [2,3]. Vertical profiles of wind speed and direction collected by ground-based instruments (e.g., radar and wind profiles) can be assimilated into numerical weather prediction models (NWP) leading to more accurate forecasts, e.g., [4,5], or for the monitoring and tracking of urban air pollution, e.g., [6,7]. High resolution wind measurements are required in the energy sector for wind power forecast applications, e.g., [8,9]. Remote Sens. 2023, 15, 1514. https://doi.org/10.3390/rs15061514 https://www.mdpi.com/journal/remotesensing