WRF (v4.0)-SUEWS (v2018c) coupled system: development, evaluation and application

The process of coupling the Surface Urban Energy and Water Scheme (SUEWS) into the Weather Research and Forecasting (WRF) model is presented, including pre-processing of model parameters to represent spatial variability in surface characteristics. Fluxes and mixed-layer height observations in the southern UK are used to evaluate a 2-week period in each season. Mean absolute errors, based on all periods, are smaller in residential Swindon than central London for turbulent sensible and latent heat fluxes ( Q H , Q E ) with greater skill on clear-sky days on both sites (for incoming and outgoing short- and long-wave radiation, Q H and Q E ). Clear-sky seasonality is seen in the model performance: there is better absolute skill for Q H and Q E in autumn and winter, when there is a higher frequency of clear-sky days, than in spring and summer. As the WRF-modelled incoming short-wave radiation has large errors, we apply a bulk transmissivity derived from local observations to reduce the incoming short-wave radiation input to the land surface scheme - this could correspond to increased presence of aerosols in cities. We use the coupled WRF-SUEWS system to investigate impacts of the anthropogenic heat flux emissions on boundary layer dynamics by comparing areas with contrasting human activities (central-commercial and residential areas) in Greater London - larger anthropogenic heat emissions not only elevate the mixed-layer heights but also lead to a warmer and drier near-surface atmosphere.