Robles, JoséZamorano Calvo, JaimePascual Ramírez, SergioSánchez de Miguel, AlejandroGallego Maestro, JesúsGaston, Kevin J.2023-06-172023-06-172021-042072-429210.3390/rs13081511https://hdl.handle.net/20.500.14352/8189© 2021 by the authors. The original manuscript was improved with the comments and suggestions received from four referees We thank The Cities at Night project for its supports. This research was funded by Secretaría Nacional de Ciencias y Tecnología de Panamá and Instituto para la Formación y Aprovechamiento de Recursos Humanos (270-2018-642); ASTRID (P-ESP-000361-0505); TEC2SPACE (S2018/NMT-4291), Programa Estatal Español de I+D+i Orientada a los Retos de la Sociedad (RTI2018-096188-B-I00); STARS4ALL (H2020-ICT-2015-688135); ACTION (H2020-SwafS-2018-1-824603); and EMISSI@N (NE/P01156x/1).Major schemes to replace other streetlight technologies with Light-Emitting Diode (LED) lamps are being undertaken across much of the world. This is predicted to have important consequences for nighttime sky brightness and color. Here, we report the results of a long-term study of these characteristics focused on the skies above Madrid. The sky brightness and color monitoring station at Universidad Complutense de Madrid (inside the city) collected Johnson B, V, and R sky brightness data, Sky Quality Meter (SQM), and Telescope Encoder Sky Sensor-WiFi (TESS-W) broadband photometry throughout the night, every night between 2010–2020. Our analysis includes a data filtering process that can be used with other similar sky brightness monitoring data. Major changes in sky brightness and color took place during 2015–2016, when a sizable fraction of the streetlamps in Madrid changed from High-Pressure Sodium (HPS) to LEDs. The sky brightness detected in the Johnson B band darkened by 14% from 2011 to 2015 and brightened by 32% from 2015 to 2019.engAtribución 3.0 Españajournal articlehttp://dx.doi.org/10.3390/rs13081511https://www.mdpi.com/open access52Artificial-lightFísica atmosférica2501 Ciencias de la Atmósfera