Estimation of mean radiant temperature in cities using an urban parameterization and building energy model within a mesoscale atmospheric model
Luxi Jin, Sebastian Schubert, Daniel Fenner, Mohamed Salim, Christoph Schneider
Abstract
During daylight hours, the mean radiant temperature T mrt is one of the most important meteorological parameters to analyse heat stress for humans. This study conducts a spatio-temporal analysis of T mrt for a summer period in 2018 for the city of Berlin, Germany. To this end, the mesoscale climate model COSMO-CLM (CCLM) is coupled with the urban Double Canyon Effect Parameterization scheme with a building energy model (DCEP-BEM) to derive T mrt . This coupled model system CCLM/DCEP-BEM enables a dynamic calculation of T mrt 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 fluxes and T mrt from CCLM/DCEP-BEM. The radiation model SOLWEIG is first validated against measurement and then used to evaluate the DCEP-BEM model. Overall good agreement in T mrt is found between CCLM/DCEP-BEM and SOLWEIG (R 2 = 0.96). Nighttime T mrt simulated with CCLM/DCEP-BEM is higher than that with SOLWEIG (MBE = 2.9 K), yet closer to measurements. T mrt 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 T mrt 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 T mrt during midday. This study provides a reliable representation of T mrt in a mesoscale model and would be beneficial for future implementation of human-biometeorological variables such as the Universal Thermal Climate Index or Physiological Equivalent Temperature. These quantities are calculated using T mrt .