how heatwave simulations affect by land surface representations in urban regions
Surface processes and thermal properties of urban areas are well known to modify the urban boundary layer and local atmospheric circulations. Understanding these synergistic interactions have substantial and extensive implications in exploring the impact of heatwave on urban areas. However, whether these interactions extend beyond urban boundaries and manifest during a heatwave event remains a question. We addressed this question by simulating the 2017 Europe heatwave using the Weather Research and Forecasting model (WRF) in four experiments. The experiments included configuring WRF with two LSMs (i.e., Noah and Noah-MP) and two urban representations (i.e., the default land use/land cover (LULC) and Local Climate Zones (LCZs) from WUDAPT).
By these experiments, we also evaluated the impact of LSMs and urban heterogeneity (using LCZs) on the simulated air temperature during the heatwave event. The results showed that implementing the LCZs significantly improved the WRF simulations in generating the daily temperature regardless of the LSMs. The lowest bias in temperature simulations was achieved when WRF was coupled with Noah and used WUDAPT as the LULC. Implementing the LCZs altered the surface energy balance partitioning (i.e., reduced the sensible heat flux, and increased latent heat flux) primarily due to a higher vegetation proportion in the LCZs.
The simulations signified a two-way feedback mechanism between urban grids and surrounding areas (likely through changing advective energy exchange, shifting urban, non-urban thermal contrast, and altering secondary circulations) that affected the temperatures outside the urban grids across Europe during the heatwave event.