Representing Agricultural Systems in Earth System Model: implementation, calibration, and multi-scale validation of CLM-AgSys

Global food security is under increasing pressure from population growth and climate change, despite continuous advancements in breeding and management technologies. Earth system models (ESMs) imbedded with crop models are promising tools to study the impacts of historical and future climate on regional and global food productivity, as well as to assess the effectiveness of possible agricultural adaptations and their potential feedback to the climate system. However, there is still a performance gap in simulating crop growth processes and their responses to climate variabilities by the crop models in current ESMs for decision-making assessments and downstream scientific analyses. Here we report the development and evaluation of an improved crop growth model (CLM-AgSys) in the framework of the Community Earth System Model (CESM). The CLM-AgSys model combined the strengths of both the Community Land Model (CLM) and the Agricultural Production Systems sIMulator (APSIM) models. The CLM-AgSys can not only achieve a high performance in simulating crop yield with the right mechanisms, but also capture the emerging responses of crop yield to climate variabilities. The presentation will cover key results from four major aspects: (1) model implementation; (2) site-level global parameter sensitivity analysis and Bayesian calibration; (3) site-level and regional evaluation over U.S. Corn Belt, and (4) model corroboration with measured data from Free Air Concentration Enrichment (FACE) and Temperature Free-Air Controlled Enhancement (T-FACE) experiments. Our results demonstrate that with improved parameterization of crop growth, the ESMs can realistically simulate responses of agricultural production to climate variabilities and change, which is critical for studying global food security and the food-energy-water nexus under climate change.