Is the Stationary Wave Bias in CMIP5 Simulations Driven by Latent Heating Biases?

Atmospheric stationary waves play an important role in regional climate. In phase 5 of the Coupled Model Intercomparison Project (CMIP5), a prior study found that there are systematic biases in Arctic moisture intrusions caused by stationary eddy meridional wind biases. In this study, using initial-value model calculations, it is shown that CMIP5 latent heating biases in the tropics and midlatitudes play a substantial role in generating the systematic meridional wind bias poleward of 50°N. It is further shown that the midlatitude heating biases are in part driven by the circulation caused by the tropical and subtropical heating biases. These results indicate that the systematic stationary meridional wind biases poleward of 50°N can be traced to systematic model biases in tropical and extratropical latent heating. Therefore, reliable regional climate projections likely hinge on accurate representations of moist processes upstream of the region of interest and in the tropics.