Spurious Drifts in the ITCZ Location and Associated Atmospheric Circulation in Decadal Climate Predictions

Decadal predictions are affected by initialization shocks and drift, typically diagnosed in ocean circulation or temperature. It is not known, however, to what extent the drift can affect atmospheric dynamics. Here we investigate how the drift causes spatial shifts in the location of key large‐scale atmospheric circulation features such as the Intertropical Convergence Zone (ITCZ). The asymmetrical changes in surface temperature (with warmer southern and cooler northern hemisphere) with increasing forecast times cause southward shifts in the location of ITCZ, the subtropical jets and tropical precipitation patterns. Such changes are larger in full‐field initialized models, however, the anomaly‐initialized models show large biases in their ITCZ location from the beginning. These artificial changes in the location of large‐scale circulation patterns pose important challenges to initialized climate predictions, potentially undermining the ability of current prediction systems to predict changes in climate aspects for which atmospheric circulation is an important driver.