Radiative and heat storage properties of the urban fabric derived from analysis of surface forms

• Urban albedo is computed at city block scale from solar simulations.
• Temperature signal time shift is calculated from three years of measurements.
• Urban albedo is strongly related to sky view factor and facade density.
• Temperature signal time shift is explained by aspect ratio H/W and facade density.
• Climatic maps could be directly produced from geographical data.

Radiative balance and heat storage capacity modifications play a major role in urban heat island formation. Urban shape determines the receipt and loss of radiation and consequently the heat storage potential, thus resulting in a higher air temperature.In order to analyze the interactions between climate and urban shape, the territory is partitioned from the road network into elementary areas: the city blocks.Nine geographical and two climatic indicators are computed at city block scale. The geographical ones are produced thanks to OrbisGIS platform from geographical data supplied by the French IGN. The first climatic indicator, the urban albedo, is computed from solar simulations with Solene model on 230 city blocks to characterize the radiative balance. The second one, the air temperature time shift, is calculated from three years of measurements between eight city blocks and a reference sites to characterize the heat storage properties of the urban fabric.Relationships between those climatic and geographical indicators are investigated using linear regression analysis. Facade density is the geographical indicator which best explains both radiative and heat storage properties at city block scale. From the relationships identified previously and geographical data, climatic maps are produced to assess urban vulnerability to climate change.