A first calibration of JULES-crop version 7.4 for rice using the novel O ₃ -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 (Joint UK Land Environment Simulator with crops, 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 and 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.