Three experimental projects are described herein concerning different spatial scales of atmospheric flows in urban areas. The first consisted of a field experiment performed in Phoenix, Arizona, focusing on flow and turbulence characteristics in a neighborhood made up of mixed industrial and suburban usage. The area is affected by larger scale terrain induced (slope/valley) flows, as well as the smaller scale land-use characteristics that have strong spatial inhomogeneity. Flow and turbulence parameterizations used in existing numerical models were tested and, where applicable, improved alternatives suggested. Calculation of integral length scales allowed a phenomenological description of eddy characteristics within and above the urban canopy layer. A detailed study of the nocturnal urban boundary layer was performed, which adds to the limited amount of literature on the subject. Secondly, an air quality study is described, conducted in an industrial area of the coastal valley of Termoli, Italy. The effects of the slope flows, sea breeze, and urban heat island (UHI) were delineated using phenomenological reasoning in order to better understand the causes of high pollution episodes. Finally, a project studying street canyon flow induced by differentially heated surfaces was carried out. Field data was collected by constructing and instrumenting a simplified mock street canyon in Singapore. A buoyancy parameter that delineates thermally and inertially driven circulations in street canyons was developed and tested. In addition, computational fluid dynamics (CFD) simulations were conducted to complement and better understand flow mechanisms observed in the field, the results of which were found to be consistent with observations.