The infrared images from the Tornado flights were calibrated with the help of synchronous Helipod flight tracks. The images, available with a spatial resolution of about 1-2 m, were then analysed with respect to the local surface temperature distribution in the footprint area around the different surface flux stations. Mean surface temperatures differed up to about 8 K for different footprint sectors. Within a certain footprint sector, we found a standard deviation of surface temperature up to about 6 K due to differences in local soil moisture and vegetation density. These temperature anomalies could be identified consistently in the images from three flights performed on different days and at different times of the day (with correlation coefficients between the temperature patterns of the different days up to r2 = 0.92).
Non-closure of the local surface energy balance was related to the surface temperature heterogeneity in the footprint area of the flux sites. It could be shown, that the size of the energy balance residuum is increased for sectors with a large standard deviation of surface temperature. We should remark that most of the obvious structures in the surface temperature field could not or just hardly be recognised in the corresponding visible site and area photographs. Surface temperature mapping should therefore be an advisable step of the site selection procedure for micrometeorological flux measurements.