Reducing Long-Standing Surface Ozone Overestimation in Earth System Modeling by High-Resolution Simulation and Dry Deposition Improvement

Gao, Yang and Kou, Wenbin and Cheng, Wenxuan and Guo, Xiuwen and Qu, Binglin and Wu, Yubing and Zhang, Shaoqing and Liao, Hong and Chen, Deliang and Leung, L. Ruby and Wild, Oliver and Zhang, Junxi and Lin, Guangxing and Su, Hang and Cheng, Yafang and Pöschl, Ulrich and Pozzer, Andrea and Zhang, Leiming and Lamarque, Jean-Francois and Guenther, Alex B. and Brasseur, Guy and Liu, Zhao and Lu, Haitian and Li, Chenlin and Zhao, Bin and Wang, Shuxiao and Huang, Xin and Pan, Jingshan and Liu, Guangliang and Liu, Xin and Lin, Haipeng and Zhao, Yuanhong and Zhao, Chun and Meng, Junlei and Yao, Xiaohong and Gao, Huiwang and Wu, Lixin (2025) Reducing Long-Standing Surface Ozone Overestimation in Earth System Modeling by High-Resolution Simulation and Dry Deposition Improvement. Journal of Advances in Modeling Earth Systems, 17 (3): e2023MS004. ISSN 1942-2466

Abstract

The overestimation of surface ozone concentration in low-resolution global atmospheric chemistry and climate models has been a long-standing issue. We first update the ozone dry deposition scheme in both high- (0.25°) and low-resolution (1°) Community Earth System Model (CESM) version 1.3 runs, by adding the effects of leaf area index and correcting the sunlit and shaded fractions of stomatal resistances. With this update, 5-year-long summer simulations (2015–2019) using the low-resolution CESM still exhibit substantial ozone overestimation (by 6.0–16.2 ppbv) over the U.S., Europe, eastern China, and ozone pollution hotspots. The ozone dry deposition scheme is further improved by adjusting the leaf cuticle conductance, reducing the mean ozone bias by 19 and increasing the model resolution further reduces the ozone overestimation by 43 revealing distinctive pathways in urban versus rural areas. In rural areas, grid spacing mainly affects daytime ozone levels, where additional NOx emissions from nearby urban areas result in an ozone boost and overestimation in low-resolution simulations. In contrast, over urban areas, daytime ozone overestimation follows a similar mechanism due to the influence of volatile organic compounds from surrounding rural areas. However, nighttime ozone overestimation is closely linked to weakened NO titration owing to the redistribution of urban NOx to rural areas. Additionally, stratosphere-troposphere exchange may also contribute to reducing ozone bias in high-resolution simulations, warranting further investigation. This optimized high-resolution CESM may enhance understanding of ozone formation mechanisms, sources, and changes in a warming climate.