Investigating the effect of land-use change on the heat load within two Austrian cities

As the majority of the population live in cities, it is important to understand the urban climate and how it can change in the future. Accordingly, the ACRP-funded project LUCRETIA investigates how land use and land cover determine local climate characteristics within cities in Austria. 

Historical land use data has been obtained for Graz and Vienna for a number of years and used as input into the microscale urban climate model MUKLIMO_3 to simulate both cities in conditions representing a typical summer day. In conjunction with the cuboid method, climate indices such as the average number of summer and hot days per year have been calculated to establish how the heat load changes from one year to another. Differences in the heat load have been related to changes in the land use focusing on (i) the change that occurs in situ and (ii) the change that occurs in the neighbourhood. 
 
It is shown that land use categories can be ordered according to their heat load, with categories containing larger amounts of greenery generally having lower heat loads. With the land use categories sorted in such a way, it enables a relatively quick assessment to be made of the effect of replacing one land use category with another, without having to employ expensive modelling tools. Furthermore, it is shown that land-use changes not only affect the heat load of the changed area in situ, but also the neighbourhood around where the change was made. This demonstrates that land-use changes may have a broader spatial impact than initially anticipated. The results from this study can serve as guidance for city planners regarding future land use and land cover changes.