Surface to boundary layer coupling in the urban area of Lisbon comparing different urban canopy models in WRF

This work presents a sensitivity study to evaluate different Urban Canopy Models (UCM) existing within the Weather Research and Forecasting Model (WRF) in the urban area of Lisbon, Portugal. Several hind-cast simulations were carried out for a selected period in July 2010, in which synoptic conditions favoured urban heat island formation. We aim to gain knowledge on the feedback of modified urban canopy representation in WRF on local scale meteorology and the boundary-layer dynamics over the urban area, by comparing a single layer urban canopy model (SLUCM) and a more sophisticated multi-layer building effect parametrisation (BEP). We find significant differences in the characteristics of the urban boundary layer between BEP and SLUCM, manifested through changes in turbulent kinetic energy (TKE) and urban boundary layer (UBL) height over the urban centre. Compared to ground observations and radiosonde data retrieved within the core urban area, both variables are better represented by BEP compared to SLUCM. Simulating perturbations of vertical wind components and temperature we can show a general amplification and displacement of modelled gravity waves over the central urban area under the prevailing synoptic conditions when a multi-layer canopy model is used instead of a single-layer model or a bulk approach.