The Role of Green Areas in Temperature and the Urban Heat Island in a Case Study of a Renovated District in the Capital City of Hungary

The built-up areas and the artificial surface covers are evidently very different from the natural environment in many aspects. For instance, the energy budget, radiation characteristics, and wind field are all modified in cities, thus creating specific urban climate. One of the most important modifications of urban areas is the urban heat island (UHI) intensity, which is the temperature difference between the densely built-up inner areas and the rural surroundings around the city. UHI effect can be detected with in-situ air temperature measurements as well as remotely sensed surface temperature data. Although the characteristics of the resulting UHI effects are usually different when using these two types of data in the analysis, they point out important features in any case. Many studies highlight the importance of green space within cities as green areas help to keep a healthier environmental for city dwellers and to keep the city more livable. More specifically, green areas certainly reduce the heat stress associated to the UHI effect.

The target area of our study is a well defined part of an urban agglomeration: Ferencváros is a very heterogeneous district of Budapest, the capital of Hungary (a Central/Eastern European country). It is located near the river Danube, which divides the capital into a more hilly western part and a more flat eastern part (Ferencváros belongs to this latter area). The local government has launched various renovation programs since the 1980’s. The main aim of these programs is to improve the environment by (i) modernizing the buildings and (ii) increasing both the number and the size of green areas in the district. In the framework of these renovation programs the old blocks of buildings were demolished, and then, new buildings were built in different structures so new green gardens could be created inside the newly built blocks. In addition, pre-existing green areas were also renovated, and some blocks remained unbuilt where new parks were created.

We investigated this renovated area on the basis of our own measurement campaigns focusing on (i) air temperature and (ii) green area characteristics. In addition, the analysis contains specific case studies using the surface temperature data of the fine-resolution ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) sensor on board satellite Terra. The main question to be answered in this study is how strong is the local moderating effect of the green areas of Ferencváros on temperature and the UHI effect of the area.