Abstract
Atmospheric Rivers (ARs) are synoptic-scale conduits for poleward
transport of heat and water, often associated with extreme rainfall.
Using NASA surface heat flux observations and climate model simulations,
we assess whether ARs are ‘rivers’, transporting heat and moisture over
longer distances, or mostly local convergence. The observations indicate
that ARs reduce extratropical surface energy fluxes, even during early
development. This damping of surface fluxes during ARs is also simulated
in the Goddard Institute for Space Studies ModelE, 2.1 (GISS-E2.1)
nudged to (MERRA2) reanalysis winds. Furthermore, water provenance
tracers in GISS-E2.1 identify the moisture source for
~7500 ARs globally during 2018-2022 as farther upstream
and equatorward compared to climatology. These results quantitatively
show that ARs source relatively less moisture from the surface beneath
them and more from a greater distance than during non-AR times.