Qualification of microclimate models and simulation tools: An academic benchmark

Abstract

In recent decades, numerous urban microclimate models have been developed to address various applications, such as diagnosing urban overheating and evaluating heat mitigation strategies using green or grey solutions. These models account for complex physical interactions; however, their qualification and validation remain significant challenges due to their complexity and the lack of a standardized framework and comprehensive reference datasets.

This paper presents the first step of a comprehensive qualification and validation methodology through the definition of an academic benchmark and its application to four urban microclimate models. The proposed methodology follows an incremental phenomenological approach, systematically analysing heat transfer processes within an idealized street canyon with well-defined conditions across four cases: shortwave radiation, longwave radiation, aeraulics, and their coupling with heat conduction and storage in walls and ground. The benchmark aims to analyse the behaviour of different microclimate models, quantify deviations between simulation results, and identify their underlying sources within the physical models. This is achieved through the intercomparison of simulation results, incorporating reference data with a known standard deviation where available.

The results show good agreement between models for solar radiation, infrared radiation, and heat conduction but reveal significant deviations in surface convection, stressing the need for further research into convection modelling and its influence on coupled processes. Additionally, the results confirm the suitability of the proposed methodology in identifying the sources of deviations between models. This benchmark provides a robust framework for model qualification and is expected to be widely adopted in future studies.