How does anthropogenic heating affect the thermal environment in a medium-sized Central European city? A case study in Szeged, Hungary

Since the estimation of anthropogenic heating is always problematic in medium-sized cities because of data lacking, we intended to test how much the omission of such data influences the physical consistency in a numerical model (Weather Research and Forecasting - WRF). It was hypothesized that anthropogenic heating is an important input for the model, even in a relatively small urban area, therefore we adapted three different approaches to quantify its spatiotemporal distribution over Szeged, Hungary. Four numerical experiments were performed in the WRF coupled with the single layer canopy scheme, which included the calculated fluxes and an anthropogenic flux-free reference case. By comparing the experiments, we had the opportunity to determine the effects of different anthropogenic heating scenarios on certain meteorological variables near the surface and in the overlying urban boundary layer. The maximum anthropogenic heat release was estimated to be ranging between 0.6 and 31.2 W/m(2) in Szeged, with higher values on winter days. This heat surplus contributed to a maximum increase of 1.5 degrees C in the simulated near-surface air temperature. Depending on the rate of anthropogenic heat release, the urban boundary layer became deeper, and the mixing of heat and momentum was more efficient. Our results have demonstrated that without the consideration of anthropogenic heating, numerical simulations performed to cities similar to Szeged cannot be physically complete.