WRF (v4.0)-SUEWS (v2018c) Coupled System: Development, Evaluation and Application

Abstract. 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 of surface characteristics. Fluxes and mixed layer height observations in the southern UK are used to evaluate a two-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 days at both sites (for incoming and outgoing short- and longwave radiation, Q_H and Q_E). Clear seasonality is seen in the model performance: with better absolute skill for Q_H and Q_E in autumn and winter, when there is a higher frequency of clear days, than in spring and summer. As the WRF-modelled incoming shortwave 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.