A first calibration of the JULES-crop version 7.4 for rice using the novel O₃-FACE experiment in China

Abstract. Ozone (O₃) pollution poses an escalating threat to rice production and food security in China, with concentrations projected to rise under future climate scenarios. Accurately quantifying O₃ impacts on rice is thus crucial for informed agricultural planning. This study is the first to utilise Free Air Concentration Enrichment (FACE) observations specific to rice for calibrating a crop model (JULES-crop) and assessing the impacts of O₃. FACE experiments, which involve growing crops under natural field conditions while exposing them to elevated O₃ levels, provide an ideal approach for studying the effects of O₃ on crops. Utilising data from the only O₃-FACE facility dedicated to rice, we calibrated physiological and O₃-response parameters in JULES-crop and evaluated the model against additional independent FACE observations. The calibration establishes this as the first crop model refined with ideal open-air field observations, significantly enhancing its capability to simulate rice growth processes and O₃-induced yield losses, surpassing the performance of simulations based on the default parameters in JULES-crop. With this newly calibrated model, JULES-crop is now equipped to assess the impacts of O₃ on agriculture, offering a valuable tool to inform mitigation strategies.