Textbooks describe the atmosphere’s north–south motion as closed circulation cells. This study shows that the water cycle also drives a subtle one-way flow of air, moving it from the humidified subtropics toward regions dried by rain and condensation. This hidden transport helps explain gradients of inert gases and suggests that large-scale atmospheric circulation may be more open than commonly assumed.

It is well-established that variations in convection in the tropical Indo-Pacific can influence weather in far-away regions. In this idea, I argue that the main theory used to explain this influence over large distances is incomplete. I propose hypotheses that could lead the way towards a more fundamental explanation and outline a novel approach that could be used to test the hypotheses I raise. The suggested approach might be useful to address also other long-standing questions.