Evaluation of WRF model PBL schemes for highly resolved WRF-BEP/BEM simulations over Nicosia urban area

Urban climate is a fast-growing research field that is gaining more and more attention for different reasons. On one side, cities include most of the inhabitants, services, and infrastructures of each country. On the other hand, the global population continues to increase, causing cities to grow denser, larger, and to become much more vulnerable to climate change impacts and threats. Moreover, replacing natural surfaces with artificial, dry, and impermeable ones causes a substantial modification of the atmospheric processes and variables at the local scale affecting the local weather and, on many occasions, enhancing the consequences of climate-induced phenomena. With this regard, atmospheric models have been widely used to understand better the dynamics of the processes happening at the local scale and to assess different adaptation strategies. In particular, three urban schemes can be implemented into the Weather Forecasting and Research model (WRF): Single Layer Urban Canopy Model (SLUCM), Building Effect Parameterization (BEP), and BEP coupled to a Building Energy Model (BEP + BEM) to parameterize the respective processes. Along with choosing the proper urban canopy model (UCM), the correct representation of the planetary boundary layer (PBL) is equally pivotal to performing realistic simulations to investigate surface variables. Therefore, in this study, we examine the performance of the WRF model coupled with the BEP and BEP + BEM urban canopy models when used with the three PBL schemes with which those UCMs can be used. Focusing on the urban heat island effect in the urban area of Nicosia during a heat wave in the summer of 2021, this study aims to (i) identify the differences among the WRF simulated near-surface atmospheric variables due to the choice of PBL schemes, (ii) quantify and understand the model biases and, based on the previous results, (iii) reveal the appropriate scheme for the most reliable set-up for urban climate simulations in the Eastern Mediterranean and Middle East (EMME) region. The PBL schemes considered are the Mellor-Yamada-Janic (MYJ), Yonsei University (YSU), and the Bougeault-Lacarrere (BouLac). We considered three nested domains to downscale the ERA5 re-analysis over the area of interest. The parent domain (d01) covers the EMME region at 12 km x 12 km horizontal resolution. The first nested domain (d02) encompasses Cyprus and the coast of the Levant region at 4 km x 4 km horizontal resolution, and the innermost domain (d03) at 1 km x 1 km horizontal resolution focuses on the city of Nicosia.