Atmospheric rivers and water fluxes in precipitating quasi‐geostrophic turbulence

Abstract

AbstractMost of the poleward transport of water can be accounted for by long narrow corridors known as Atmospheric Rivers (ARs). ARs are typically associated with extratropical cyclones and, for dry extratropical cyclones, an idealized prototype has previously been provided by quasi‐geostrophic (QG) dynamics. However, there are few if any studies that investigate ARs in a QG framework. Here, the overarching question is: do idealized ARs appear in moist QG dynamics? A precipitating quasi‐geostrophic (PQG) model is explored as a possible prototype for ARs and associated water transport. The set‐up uses numerical simulations of geostrophic turbulence with precipitation, in a single phase. The simulations are shown to produce idealized ARs, and they have reasonably realistic statistics for such a simple set‐up. For instance, the model ARs occur roughly as frequently as in nature, based on commonly used AR identification algorithms. To produce ARs in this model, it is found that two key ingredients are needed beyond the dry QG framework: precipitation and a meridional moisture gradient. If either of these two ingredients is too weak, then less realistic ARs are produced. In addition, for a range of precipitation rates, a large fraction of the meridional moisture transport is due to ARs.