Coupling the Town Energy Balance (TEB) Scheme to an Operational Limited-Area NWP Model: Evaluation for a Highly Urbanized Area in Belgium

Abstract

he Town Energy Balance (TEB) single-layer scheme is implemented in a numerical weather prediction model running operationally at ~4-km resolution. The primary question addressed is the ability of TEB to function at this relatively coarse resolution and, thus, assessing its potential use in an operational configuration to improve sensible weather performance over Belgium. For this effort, simulations with and without TEB are first evaluated against 2-m observations and wind above the urban canopy for two months (January and July 2010). The results show that promising improvements are achieved by introducing TEB. The 2-m temperature and 2-m relative humidity improve compared to measurements in urban areas. The comparison of wind speed and wind direction above the urban canopy indicates that the structure of the flow in urban areas is better reproduced with TEB. It was found that the implementation of TEB results in an increase in winter precipitation over urban areas and downwind from urban areas, but during the summer TEB tended to cause rainfall to be locally concentrated and the total accumulated precipitation decreased obviously. Results from a 36-h case study during a high heat day with inland sea-breeze penetration (8 July 2010) indicate that the model satisfactorily captured the penetration of the sea breeze. In particular during the day, the TEB run shows a delay in the sea-breeze evolution compared to the operational run. During the night the results indicate that even at this coarse resolution, TEB is able to correctly reproduce the intensity of the observed urban heat island (UHI) of Brussels.