Daily and seasonal fluxes in the city of Sassari

Cities present structural and morphological characteristics allowing to absorb and trap more solar and thermal radiation than natural ecosystems (soils or vegetation), thus reflecting an increase in the urban temperature. In addition, human activities such as the heating and the cooling of buildings, traffic, various industrial activities and human metabolism release energy in the form of heat, as well as greenhouse gases (GHG) (mainly carbon dioxide). All these processes have an impact on the urban climate by modifying the energy flux partitioning and the carbon budget. One year of urban fluxes measurements was carried out in the city of Sassari, located in the north of Sardinia Island (Italy), to study the exchange of energy, water, and carbon over the city, evaluate their impact on human livability, and understand the main factors or activities affecting them. The measured fluxes were sorted by wind direction to better investigate the role of the reduced vegetation area (< 20% in the measurement footprint) in decreasing anthropogenic fluxes, which could help the municipality to identify possible actions for mitigating human impact. Daily trend showed the traffic as one of the main sources of carbon emissions, with two distinguishable peaks clearly related to the rush hours during the working days (morning and evening peaks), but an additional peak was observed during lunch time, that makes this Mediterranean city different from other at higher latitudes. Also, seasonal trends and differences between working days, weekends and holidays are reported.