Assessing the relationship between Urban Morphology and Mean Radiant Temperature - A study over 5 cities in Sweden
Abstract
Thermal comfort has become an increasingly important topic in urban areas due to climate
change and rapid urbanization. The most critical meteorological variable influencing
experienced heat and thermal comfort during warm and clear weather is the mean radiant
temperature (Tmrt). This study examines how the thermal environment is influenced by
variations in urban morphology. Modeling of Tmrt using SOLWEIG was performed for five
cities in Sweden: Malmö, Gothenburg, Stockholm, Östersund, and Luleå. For each city,
simulations were executed twice - once including vegetation and ground cover, and once
without. This approach allowed for a clearer assessment of the influence of vegetation and
urban geometry on the thermal environment. The results for each city were compared,
identifying the most influential variables affecting Tmrt.
The findings indicate that trees have the highest influence and correlation with lower Tmrt in
urban areas, primarily due to the shade they provide. The impact of trees varies depending on
the surrounding urban geometry, with their cooling effect diminishing in denser areas,
especially those with tall buildings. The relationship between urban geometry and the thermal
environment is complex, with many variations on a microscale. On average, higher density
leads to lower Tmrt over an entire 500 x 500mcell for an entire day. Due to morphological
differences among the five cities, Malmö emerged as the warmest city thermally, mainly due
to its low number of trees. Conversely, Luleå was the least thermally warm city, showing the
highest decrease in Tmrt for both geometry and vegetation. Despite having the fourth-lowest
density and tree fraction, Luleå's results suggest that solar altitude significantly influences
Tmrt, indicating that the geographical location of cities affects the spatial variations of Tmrt.
Degree
Student essay