Abstract
We report the ability of an urban canopy model, coupled with a regional climate model, to simulate energy fluxes, the intra-urban variability of air temperature, urban-heat-island characteristics, indoor temperature variation, as well as anthropogenic heat emissions, in Berlin, Germany. A building energy model is implemented into the Double Canyon Effect Parametrization, which is coupled with the mesoscale climate model COSMO-CLM (COnsortium for Small-scale MOdelling in CLimate Mode) and takes into account heat generation within buildings and calculates the heat transfer between buildings and the urban atmosphere. The enhanced coupled urban model is applied in two simulations of 24-day duration for a winter and a summer period in 2018 in Berlin, using downscaled reanalysis data to a final grid spacing of 1 km. Model results are evaluated with observations of radiative and turbulent energy fluxes, 2-m air temperature, and indoor air temperature. The evaluation indicates that the improved model reproduces the diurnal characteristics of the observed turbulent heat fluxes, and considerably improves the simulated 2-m air temperature and urban heat island in winter, compared with the simulation without the building energy model. Our set-up also estimates the spatio–temporal variation of wintertime energy consumption due to heating with canyon geometry. The potential to save energy due to the urban heat island only becomes evident when comparing a suburban site with an urban site after applying the same grid-cell values for building and street widths. In summer, the model realistically reproduces the indoor air temperature and its temporal variation.
Highlights
Within cities, near-surface air temperatures are typically higher than in their rural surroundings
We explore the impact of anthropogenic heat emissions from the building interior onto the exterior in the urban area of Berlin, the response of indoor temperature to outdoor temperature during the summer period, and the spatio–temporal variation of simulated energy consumption due to anthropogenic heat including heating systems in the winter period
The building energy models (BEM) approach based on Salamanca et al (2010) is developed for the urban canopy model DCEP and coupled with the mesoscale climate model CCLM
Summary
Near-surface air temperatures are typically higher than in their rural surroundings. Fan and Sailor (2005) detected an increase of the UHI intensity of 2 K to 3 K during a winter night in Philadelphia, U.S.A. In summer, waste heat originating from air conditioning systems affects air temperatures in urban areas in low/mid-latitude (Ohashi et al 2007; Chow et al 2014; Salamanca et al 2015; Takane et al 2017). Various applications for different cities verified the ability of this approach to reproduce temperatures and flow properties (Salamanca et al 2011, 2012), and the citywide diurnal cycle of electricity consumption due to air conditioning (Salamanca et al 2013, 2014, 2015) Another approach to incorporate anthropogenic heat into climate models is to prescribe the surface anthropogenic heat flux at the lowest layer of the atmosphere (Flanner 2009; Wouters et al 2015, 2016).
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