Atmospheric rivers (AR) are long, narrow jets of moisture transport responsible for over 90% of moisture transport from the tropics to higher latitudes, covering only between 2% and 10% of the earth’s surface. ARs have a significant impact on the hydrological cycle of midlatitudes and polar regions, which has resulted in a large effort to study ARs and their impacts on these regions. It is not until recently that ARs in tropical latitudes are starting to generate interest within the scientific AR community.
We use the ERA-20C reanalysis and the Bayesian AR detector TECA-BARD to show the relationship between extreme precipitation and atmospheric rivers in central-western Mexico (CWM) during the dry seasons (November-March) in the 1900-2010 period.
We find that more than 25% of extreme precipitation amount and frequency are associated with ARs, with a maximum of 60%-80% during December and January near the coast of Sinaloa (107.5W,25N). Composites of the mean meteorological state show “ideal” conditions for orographic precipitation due to landfalling ARs: high horizontal vapor transport perpendicular to the Sierra Madre. We observe a tropospheric wave pattern in vertical velocity, surface pressure, and geopotential height associated with these events. The nature and evolution of these waves need to be further studied. Our results suggest that TECA-BARD provides a reasonable estimation for AR presence in CWM. Nevertheless, we recommend using multiple AR detectors and one tuned explicitly for tropical latitudes. This will allow investigation of the response of CWM landfalling ARs and the region’s hydroclimatology under future climate scenarios.