Enhancing Urban Canopy Parameterization for Non-building Resolving Resolution Simulations: Integrating the Double Canyon Effect Parameterization (DCEP) Scheme into PALM

Abstract

This study presents the integration of the Double Canyon Effect Parameterization (DCEP) into the microscale urban climate model PALM, specifically tailored for non-building resolving resolution simulations (~100m), where individual buildings are not explicitly resolved. The DCEP scheme introduces a sophisticated scheme characterizing street canyons by considering building and street width, orientation, and building height distribution. This implementation allows for the efficient representation of buildings while maintaining computational feasibility through parallelized computations, making it suitable for large-scale simulations. The DCEP scheme explicitly accounts for the energetic exchanges between buildings and the atmosphere across multiple vertical layers, capturing the dynamics of urban surfaces as well as the storage of energy within surfaces. To derive the necessary Urban Canopy Parameters (UCPs) for DCEP, traditionally requiring high-resolution data, we employ an approach based on Local Climate Zones (LCZ). The LCZ classification, consisting of 17 classes, provides the characteristics of various urban areas, allowing for a detailed representation of heterogeneity in different zones. This approach streamlines the derivation of UCPs by assigning typical parameters to land-use categories, thereby overcoming the complexity associated with high-resolution data processing. The pre-processor tool "palm_csd" has been expanded to directly read LCZ data in different projections and resolutions, providing users with the flexibility to customize parameters assigned to each LCZ class within defined limits. Simulations were conducted over a large domain to show the impact of the PALM/DCEP coupled model. Comparative analyses were performed between simulations with the base PALM model and the enhanced PALM/DCEP coupled model. The results highlight the significant contributions of the DCEP scheme in enhancing urban and environmental modeling during non-building resolving resolution simulations. This research contributes valuable insights into the adaptability and effectiveness of the DCEP approach in simulating large urban areas where building-resolving resolution is not practical. The findings pave the way for advancements in urban climate modeling, with implications for urban planning and environmental management in diverse urban landscapes.