1 International Symposium on Applied Geoinformatics (ISAG2021) INNER COURTYARDS THERMAL BEHAVIOUR IN GRAZ DERIVED FROM AIRBORNE THERMAL SCANNER FLIGHTS Wolfgang Sulzer 1 , Daniela Hirländer 1 1 University of Graz, Department of Geography and Regional Science, Graz, Austria (wolfgang.sulzer@uni-graz.at); ORCID 0000-0001-6040-2405 Introduction Urban areas are heavily modified in terms of surface temperatures (UHI: Urban Heat Island) relative to their rural environment. By means of airborne or satellite-based Earth observation, it is possible to find out changes in radiation and energy flux densities in the mesoclimate of the city. According to Lazar et al. (1994); Lazar & Sulzer (2013), the climate of inner courtyards is determined mainly through ventilation conditions which in order are primarily influenced by the size and the number of floors. Land cover and sealing aspects play a significant role in the modification of surface temperatures in a city. In the presented paper, the surface temperature data, derived from multitemporal (different years and seasons, and during a day) thermal scanner surveys of the years 1986, 2004 and 2011, as well as the degree of sealing, the land use, the land cover and the climatop, were summarized in a geodatabase. With this GIS-based information, it is possible to analyze the thermal behavior of different inner courtyards according to their underlying surfaces as well as their size. This paper is dedicated to GIS and Remote Sensing based data preparation and methodology development, following by the analysis of results based primarily on statistical evaluations of the derived geodatabase. Data and Methods In this analysis, the land surface temperatures derived from the airborne thermal scanner flights of the years 1986, 2004 and 2011 and the respective data for the land cover, the land use, the predefined climatop and the sealing degree of each year of the city of Graz were used to identify modification of the land surface temperature in the inner courtyards. Because of the different sensors, different pre-processing steps and diverse data formats used for collecting the surface temperature and the other information, some additional pre-processing steps were necessary to homogenize the data before importing all into one geodatabase. The urban structure data is divided into several different categories and was used for the extraction of the foundation structure. It also contains the layer foundation structure, which is essential for the underlying work and did almost not change over the years what makes sense, as it is an old structure from the 19th century. Also, the other datasets, like the sealing degree, the land cover and the climatop were predefined (Lazar & Sulzer 2013; Sulzer, 2018). It is being evaluated if, based on the available data, a relation between thermal behavior of inner courtyards and their size as well as their sealing degree and vegetation cover can be identified. Not yet discussed in this context will be the influence of the number of floors and the height of the buildings and their orientation to the main local wind system.