How have the temperature and urban heat island evolved in Madrid and its surroundings in the last decades?

The intensity of the Urban Heat Island (UHI) has traditionally been studied by evaluating the temperature difference between an urban observatory and a nearby rural one. Additionally, relationships have been established between this intensity and the city’s population. However, the characterization of urban warming is very complex, and such approaches may not be totally suitable for analysing this phenomenon. The global increase in temperatures due to climate change, the varying urban development across different parts of the city and its surroundings, as well as the use of air conditioning, make urban warming potentially heterogeneous. The intensity of the UHI also varies depending on the season and meteorological conditions (wind, cloud cover, surface pressure, and precipitation), linked to different synoptic situations, tending to be more intense during stable conditions. In the case of Madrid, with a population of around 3.3 million, the UHI is relatively frequent. In this study, we use the Madrid-Retiro meteorological station (located in the city centre) as the urban one and the Barajas airport station as the rural one (located 12 km from the city centre). Additionally, other stations within a 20 km radius of the centre are used, which were initially considered rural but have experienced varying degrees of urban development over the past few decades. All stations share a common measurement period from 1961 to the present, which allows us to investigate the main objectives of the work: a) To identify and analyse temperature trends (maximum, minimum, mean) at all stations, b) To evaluate the intensity of the UHI under different meteorological conditions, examining the associated synoptic situations, c) To analyse possible trends in the intensity of the UHI.