Dottorato in INGEGNERIA AMBIENTALE E IDRAULICA

Titolo della tesi: A Three-Dimensional Urban Canopy Model for Simulating the Surface Energy Budget in Urban Areas

The combined effect of global climate change and rapid urban growth makes people living in cities more vulnerable to several environmental problems such as extreme weather and climate conditions, poor air quality, heat waves and floods. In light of this, it is important to understand how the urban texture affects the surface energy budget in order to improve knowledge essential in tools for human comfort-response strategies for builtenvironments. A great effort has been made in the last decades to couple urban canopy models (UCMs) with numerical weather prediction models (NWPMs). Most of the UCMs reported in the literature are based on the surface energy budget performed considering a simplified approach, where the two-dimensional street canyon is assumed as the basic unit to mimic the urban canopy (2DUCM). The aim of this work is to improve the modeling of the surface energy budget in UCMs by considering the actual three-dimensional nature of the urban texture. A new threedimensional urban canopy model (3DUCM), in which every single building of the city is taken into account, has been developed. Unlike 2DUCMs, 3DUCM predicts the variable of interest at the building scale. Its potentialities have been investigated considering a virtual city simulated numerically by coupling 3DUCM with the Colorado State University Mesoscale Model (CSUMM). Among the main results, it has been shown that surface and air temperatures simulated by the new model are lower compared to those predicted by 2DUCMs of the kind integrated in currently used NWPMs, mainly because of explicit crossroads modelling. 3DUCM has also been employed to investigate how buildings with different morphological characteristics and construction materials can lead to different thermalfields at the building scale. Finally, the coupled system CSUMM-3DUCM has been used to simulate the energy budget for the city of Rome (Italy). The results show that the new model can solve the thermal inhomogeneities intrinsic of the urban fabric even for a real environment.