The Regional Climate-Chemistry-Ecology Coupling Model RegCM-Chem (v4.6)-YIBs (v1.0): Development and Application

Abstract. The interactions between the terrestrial biosphere, atmospheric chemistry, and climate involve complex feedbacks that have traditionally been modeled separately. We present a new framework that couples the Yale Interactive terrestrial Biosphere (YIBs), a dynamic plant-chemistry model, with the RegCM-Chem model. RegCM-Chem-YIBs integrates meteorological variables and atmospheric chemical composition from RegCM-Chem with land surface parameters from YIBs. The terrestrial carbon flux calculated by YIBs, are fed back into RegCM-Chem interactively, thereby representing the interactions between fine particulate matter (PM_2.5), ozone (O₃), and carbon dioxide (CO₂). For testing purposes, we carry out a one-year simulation (2016) at a 30 km horizontal resolution over East Asia with RegCM-Chem-YIBs. The model accurately captures the spa-tio-temporal distribution of climate, chemical composition, and ecological parameters. In particular, the estimated O₃ and PM_2.5 are consistent with ground observations, with correlation coefficients (R) of 0.74 and 0.65, respec-tively. The simulated CO₂ concentration is consistent with observations from six sites (R ranged from 0.89 to 0.97) and exhibits a similar spatial pattern when compared to carbon assimilation products. RegCM-Chem-YIBs produces reasonably good gross primary productivity (GPP) and net primary productivity (NPP), showing seasonal and spatial distributions consistent with satellite observations, and mean biases (MBs) of 0.13 and 0.05 kg C m^-2 year^-1. This study illustrates that the RegCM-Chem-YIBs is a valuable tool to investigate coupled interactions between the terrestrial carbon cycle, atmospheric chemistry, and climate change at a higher resolution in regional scale.