Assessment of LSASAF SEVIRI land surface temperature for monitoring regional-local conditions and urban climate in the Paris region

Land surface temperature (LST) satellite products offer extensive spatial and temporal coverage, making it possible to map temperature contrasts over different territories and evolution according to weather conditions. This data is frequently used for monitoring the surface urban heat island (SUHI) of cities. But SUHI maps can raise issues of misinterpretation when trying to make the link with air temperature and related canopy-level urban heat island (UHI), and impacts on thermal comfort and heat exposure.

The aim here is to explore the potential contribution of LST satellite data for monitoring and studying regional to local-scale urban climate in the Paris region during summer 2022. Especially, we investigate the value of the EUMETSAT LSASAF product derived from the SEVIRI radiometer aboard the MSG geostationary satellite, whose 15-minute frequency makes it particularly interesting for fine temporal monitoring, despite its limited horizontal resolution of 3-5 km (which should be refined with the new MTG-I mission).

We first compare the SEVIRI LST data with those provided by the AVHRR and MODIS radiometers aboard polar-orbiting satellites, with finer 1-km resolution but only one day-time and one night-time passes. We question the relevance of pass times and investigate how satellite LST and ground-station air temperature compare depending on time of the day, types of environment, or weather conditions. This study highlights the relevance of SEVIRI for monitoring LST diurnal regimes and patterns on a regional/local scale, with promising future applications. We note that the agreement between nighttime SUHI and UHI depends on the meteorological conditions of turbulence, which govern surface-atmosphere exchanges. For very steady conditions with little turbulence, SUHIs and UHIs are particularly comparable and of greater intensity. In more mixed conditions, the urban-rural differences are less marked in LST but a good correspondence between air temperature and LST is observed in the city center.