Rivers in the sky

Two new papers help the layman hydrologist catch up on the flourishing science of atmosheric rivers.

The first is a superb review by Ashley Payne and colleagues, published here in Nature Earth and Environment. If you want a primer on atmospheric rivers, this is for you. It’s wonderfully written and jammed with data.

How about this for an opener:

Atmospheric rivers are synoptic-scale features characterized by their striking geometry—extending thousands of kilometres in length and an order of magnitude less in width—and vertically coherent low-level moisture transport concentrated in the bottom 3km of the atmosphere.

So why are atmospheric rivers important?

ARs provide 20–30% of annual precipitation in western Europe and the western USA, and 14–44% of warm-season total precipitation in East Asia.

ARs contribute approximately 22% of the global run-off, reaching 50% in certain regions

The impacts of ARs are not limited to riverine flooding; 40–60% of annual sea-level maxima at several sites along the West Coast were also connected to AR storm events

…in regions currently frequented by ARs, the recurrence of droughts would increase by up to 90% in the absence of ARs, due to both the immediate precipitation responses and the longer-term persistence of soil moisture after the event itself

(There’s much, much more in the paper).

Then yesterday the Bulletin of the American Meteorological Society (BAMS) published some notes from an expert panel discussing the Atmospheric River Tracking Intercomparison Project (ARTMIP). ARTMIP aims to gather and formalize the various methods of tracking atmospheric rivers. This is much less accessible than the Payne et al. review paper, but reading it gives one a sense of the sophistication and maturity of this burgeoning science.

Link to the BAMS paper here.