This project, conducted in collaboration with the Royal Meteorological Institute of Belgium, focused on the determination of surface parameters that characterize certain thermo-physical characteristics of cities. In particular, we considered the thermal roughness length, which governs the exchange of heat between surfaces and the overlying atmosphere; moreover, we considered the thermal admittance of urban surfaces. Use was made of thermal infrared imagery from the SEVIRI sensor on-board the Meteosat geostationary satellite platform, for the area of Paris. Values of thermal roughness length and thermal admittance were obtained by comparing simulated land surface temperature with remotely sensed values. We found that, while thermal admittance is only slightly different for cities as compared to rural areas, the thermal roughness length is many orders of magnitude smaller for cities as compared to natural rough surfaces.
Figure: Simulated (solid lines) versus SEVIRI-based (symbols) surface temperature over central Paris, 29 June 2006, as a function of time (UT, in hours). Results obtained with the (left) Zilitinkevich, (middle) “kB-1 =2,” and (right) Brutsaert/Kanda parameterizations for the thermal roughness length. The different colors denote different values of thermal inertia, ranging from 800 Jm-2s-1/2K-1 (dark red) to 2600 Jm-2s-1/2K-1 (dark blue) values. The symbols represent observed land surface temperature from SEVIRI using the split-window method. These results are published in De Ridder, K.et al J. Geophys. Res. 2012, 117, 1–14.