Interactions between extreme climate and urban morphology: Investigating the evolution of extreme wind speeds from mesoscale to microscale

This paper investigates the interactions between urban morphology indicators and extreme weather variables. In this regard, variations of wind speed and air temperature at the urban microscale are studied for three urban morphologies by means of numerical simulations. Each urban model contains ninety-nine calculation points at different locations and heights to assess the variations during two 24-h cycles of extreme low and high wind speeds by introducing a microscale indicator. According to the results, transforming from mesoscale to microscale can considerably dampen the magnitude of wind speed (up to 66%) and amplify the air temperature (up to 39%). Moreover, the urban morphology parameters (layout geometry, final height and urban density) can change the average magnitude of wind speed (up to 23%) and air temperature (up to 16%) at microscale. For extreme low wind speeds (0.16-1.14 m/s), strong correlations exist between the mesoscale and microscale magnitude of wind speed and air temperature, while there is no significant correlation for extreme high wind speeds (12.2-14 m/s). For extreme low wind speeds, stronger buoyancy effects are observed at the urban canopies. An easy-to-setup approach is proposed to count for microscale conditions during extreme low wind speeds in urban climate studies.