Impact of Different Land Uses on Local Climate in the Stockholm Region

Abstract

More than half of the world’s population lives in urban areas as a result of the ongoing urbanization. Therefore, it is important to understand the characteristics of urban climate, such as the urban heat island (UHI). To do this, well performing, high resolution climate models are needed. This study evaluates how well the Weather Research and Forecasting (WRF) model can reproduce summer 2 m air temperature (T2m) of 2018 over cities with various sizes and areas with different land use in terms of urban/non-urban over the Stockholm region. Six WRF simulations were carried out with land use classification from Local Climate Zones (LCZ). To evaluate the performance of the model, observation data from eleven Swedish Meteorological and Hydrological Institute (SMHI) weather stations in the area were used. The location of the stations was classified as urban or rural, where the urban stations were divided into city size groups based on the number of inhabitants in the city of the urban station. It was found that the highest correlation was between the simulations with revised urban parameters and the observation for the urban areas with a correlation coefficient between 0.90-0.91. However, an overestimation of the modelled daytime T2m occurred for all city size groups where the overestimation decreased with increased city size. The study concludes that WRF reproduces T2m more accurately for urban areas compared to rural areas and that the model is able to capture the UHI effect for medium to large cities. The modelled overestimation of the T2m might be because of a mismatch in land use, however, further investigation is needed to verify the cause.