Integration of an LCZ-based classification into WRF to assess the intra-urban temperature pattern under a heatwave period in Szeged, Hungary

During the simulation of the urban heat island phenomenon, the accurate representation of urban geometry in numerical models is crucial. In this study, the local climate zone (LCZ) system was incorporated into the Weather Research and Forecasting (WRF) model in order to facilitate proper land surface information for the model integrations. After the calculation of necessary input canopy parameters, based on local static datasets, simulations were performed to test the model's performance in predicting near-surface air temperature (T-a) and urban heat island intensity (Delta T) under a heatwave period in July 2017. The modelled values were evaluated against the observations of the local urban climate monitoring system. The results suggest that WRF with a single-layer canopy scheme and the LCZ-based static database was able to capture the spatiotemporal variation of the aforementioned variables reasonably well. The daytime T-a was generally overestimated in each LCZ. At nights, slight overestimations (underestimations) occurred in LCZ 6, LCZ 9, and LCZ D (LCZ 2 and LCZ 5). The mean Delta T was underestimated in the night-time; however, the daytime Delta T was estimated accurately. The mean maxima (minima) of Delta T were underestimated (overestimated) with around 1.5-2 degrees C, particularly in LCZ 2 and LCZ 5. Some components of the surface energy budget were also computed to shed light on the inter-LCZ differences of T-a. It was concluded that the nocturnal ground heat flux was about five times higher in urban LCZs than in the rural LCZ D, which resulted in a reduced cooling potential over the urbanized areas.