Impact of urban canopy physics and detailed urban canopy parameters on high-resolution simulation over two large urban agglomerations in China

Urban physics schemes and urban canopy parameters (UCPs) are vital for fine-scale weather simulations. This study evaluates the impact of different urban canopy schemes and high-resolution UCPs on meteorological fields over two largest urban agglomerations in China against dense automated weather stations for a summer day case with a high-resolution regional operational model. Results show that the single layer urban canopy model (SLUCM) with more realistic building heights mainly has a cool effect which increases the cold bias while decreases the warm bias over the YRD (Yangtze River Delta) and PRD (Pearl River Delta) region, respectively. The simulated 2-m temperature (t2) with the multi-layer urban canopy model (BEP) is slightly better than that of the SLUCM. The SLUCM with optimized building heights significantly reduces overestimation of the 10-m wind speed (ws10). The BEP scheme is obviously superior to SLUCM in ws10 simulation throughout the day over the entire region. The use of gridded UCPs in BEP only has a marginal improvement for t2 and ws10 simulation which may be due to the offset of opposite effect for areas with low and tall buildings. Planetary boundary layer (PBL) scheme has a large impact on the performance of SLUCM over the YRD region: Boulac scheme improves (degrades) the underestimation (overestimation) of nocturnal t2 (ws10) compared to the YSU scheme. This study provides guidance for applying urban canopy schemes into regional operational models and improves understandings of key processes over urban areas. •SLUCM with optimized building heights decreases (increases) warm (cold) biases.•The BEP model is superior to SLUCM in wind speed simulation.•Gridded UCPs only improves wind speed simulation for areas with tall buildings.•Performance of SLUCM is sensitive to PBL schemes particularly over the YRD region.