Modeling the impact of urbanization on local meteorological conditions in Sofia

Increasing urbanization impacts the local meteorology and the quality of life for residents. Urban surface characteristics and anthropogenic heat stress lead to urban heat island effects, changes in local circulations, precipitation alteration, and amendment of the local fluxes. These modifications have a direct effect on the life and health of residents. In this study, we assessed the impact of urbanization in Sofia (Bulgaria) using theWeather Research and Forecasting (WRF) model at 500 m resolution for the summer period of 2016. We utilized the CORINE (coordination of information on the environment) 2012 land cover database to represent the urban areas in four detailed land cover types, i.e., high-intensity residential areas, low-intensity residential areas, medium/industrial areas, and developed open spaces. We performed two experiments; in the first, we substituted an urban area with the most representative rural land cover to delineate the current impact of urbanization, while in the second, we replaced the existing built-up area (all four categories) with a hypothetical scenario of high-density residential land cover showing aggressive urban development. These experiments addressed the impact of land use changes as well as the extreme effects of ongoing high-density construction on the local meteorological conditions. The results showed that urban temperatures can increase by 5 °C and that moisture can decrease by 2 g/kg in the central part of Sofia in comparison to surrounding rural areas. The results also showed that building higher and dense urban areas can significantly increase heat flux and add additional stress to the environment.