Estimation of mean radiant temperature in cities using an urban parameterization and building energy model within a mesoscale atmospheric model

Abstract

During daylight hours, the mean radiant temperature Tmrt is one of the most important meteorological parameters to analyse heat stress for humans. This study conducts a spatio-temporal analysis of Tmrt for a summer period in 2018 for the city of Berlin, Germany. To this end, the mesoscale climate model COSMOCLM (CCLM) is coupled with the urban Double Canyon Effect Parameterization scheme with a building energy model (DCEP–BEM) to derive Tmrt . This coupled model system CCLM/DCEP–BEM enables a dynamic calculation of Tmrt for the microscale urban street canyons using a mesoscale model. To bring a more accurate comparison, a two-step approach is applied to assess the radiative fl xes and Tmrt from CCLM/DCEP–BEM. The radiation model SOLWEIG is firs validated against measurement and then used to evaluate the DCEP–BEM model. Overall good agreement in Tmrt is found between CCLM/DCEP–BEM and SOLWEIG (R2 = 0.96). Nighttime Tmrt simulated with CCLM/DCEP–BEM is higher than that with SOLWEIG (MBE = 2.9 K), yet closer to measurements. Tmrt during the afternoon hours modeled with CCLM/DCEP–BEM is underestimated compared to SOLWEIG (MBE = −3.1 K). Further, excluding vegetation, higher values for nighttime Tmrt are found in the densely built-up city center than in the suburbs with more open structures, while the city center has lower values for Tmrt during midday. This study provides a reliable representation of Tmrt in a mesoscale model and would be benef cial for future implementation of human-biometeorological variables such as the Universal Thermal Climate Index or Physiological Equivalent Temperature. These quantities are calculated using Tmrt .