Impacts of Tropical and Extratropical Diabatic Heating on Stationary Wave Forcing and Arctic Warming

During boreal winter, the climatological stationary waves play a key role in the poleward transport of moisture and heat in mid- and high-latitudes. Boreal winter stationary waves are forced by tropical and extratropical latent heating, topography, and transient eddy vorticity fluxes. Therefore, one may hypothesize that an intensification of the climatological heating can generate waves that reinforce the climatological stationary wave. A previous study tested this hypothesis and found that anomalous tropical convection that constructively interferes with the climatological convection in the tropics indeed leads to an amplification of climatological stationary wave. Moreover, this wave amplification is followed by a warming of the Arctic.

In this study, we investigate how anomalies in tropical and extratropical diabatic heating contribute to stationary wave interference, as well as the subsequent impact of this interference, by performing observational data analyses and idealized model experiments. The observational analysis shows that constructive (destructive) stationary wave interference tends to be preceded by enhanced (suppressed) tropical Pacific warm-pool convection and then followed by enhanced (suppressed) heating over the North Pacific and North Atlantic, and a warming (cooling) of the Arctic. If constructive interference takes place when both the tropical and extratropical diabatic heating are weak, constructive stationary wave interference does not lead to Arctic warming.

Initial value calculations show that the tropical heating (extratropical heating) is an important driver of wave interference over the North Pacific (North Atlantic) Ocean. However, the model calculations also suggest that the extratropical heating tends to be augmented by the tropical heating, because the latter drives a circulation which transports moisture into the extratropical heating regions. Our results show that there are different flavors of stationary wave interference, and interference that is driven by both tropical and extratropical diabatic heating leads to a particularly prolonged Arctic warming.