Land surface temperature: remote sensing of wintertime urban heat islands
Several factors (e.g. urban areas have different thermal characteristics than surrounding non-urban areas and district heating in the winter) contribute that urban heat islands occur inside cities, i.e., part of the city with higher land surface temperature than its outlying areas. This effect is generally more pronounced in larger urban areas in late afternoon/early night and particularly in hot summer or cold winter days. LSA SAF land surface temperature (LST) derived from geostationary and polar-orbiting meteorological satellites is useful for monitoring and detecting urban heat islands.
Madrid is located on the Meseta plateau in the centre of Spain and has a dry continental climate. It is one of the biggest metropolitan areas in Europe by population. Nights can get cold in winter and it has a good location to study urban heat islands because of its dry climate (cloud free conditions are necessary in order to calculate LST from measurements in infrared spectrum).
Zoom over Madrid area reveals parts of the city with higher LST (5 December 2017 20:45 UTC). The difference in LST between the centre of Madrid and areas out of city was 5-6°C (geostationary satellite MSG, left figure). METOP‘s image (right figure) displays quite a similar temperature difference between central and outlying areas although it is possible to detect more spatial details because of METOP‘s higher spatial resolution. With the next generation of EUMETSAT’s geostationary satellites one will be able to obtain METOP like spatial resolution with a high temporal frequency.