Validation of satellite observed thermal emission with in-situ measurements over an urban surface

The Basel Urban Boundary Layer Experiment (BUBBLE) is a joint European research project under the umbrella of COST (Coopération Européenne dans la domaine de la recherche Scientifique et Technique, COST 715: Meteorology applied to urban pollution problems). Besides very detailed field measurements of the structure and dynamics of the urban boundary layer, a series of satellite data has been analyzed and validated. Satellite data from MODIS, NOAA-AVHRR (14, 15, and 16) and Landsat-ETM were used and recorded during June and July 2002 in parallel to the BUBBLE field campaign. MODIS and NOAA-AVHRR data represent day and nighttime surface radiation temperatures in 930 m and 1100 m grid size. Landsat-ETM offers a unique resolution on 60 m, but with only daytime imagery at about the same time of MODIS overpass is available. This enables the validation of satellite measurements from different sensors with ground measurements at locations with various degrees of spatial homogeneity/heterogeneity (urban/rural land use). Several different algorithms for NOAA-AVHRR data were compared with in-situ measurements. The results show a very high correlation of the long wave emissions measured by the satellite with the in-situ measurements showing an accuracy of ± 3% to 5% on average, even in urban environments.