Sources of biases in blocking representation in climate models

Despite decades of research, climate models have failed to produce a consistent picture about regional variations in atmosphere blocking. The lack of sufficient model outputs has impeded the progress in unraveling the sources of biases in the model simulations. To address this issue, we perform a systematic analysis of blocking events, from two state-of-the-art climate models  with high temporal and spatial resolution — Community Earth System Model, Large Ensemble Community Project 2 (CESM LENS2) and the Norwegian Earth System Model medium resolution (NorESM2-MM) —alongside an idealised simulation featuring regionally varying CO2 forcings. A benchmark dataset of blocking events is created using the finite-amplitude local wave activity metric since it captures the growth and decay of high-amplitude Rossby waves while conserving wave activity density up to higher accuracy.  We also perform a detailed analysis of the wave activity budget to quantify the dominant physical processes that lead to biases in historical runs and processes that shift blocking patterns in warming scenario model runs.