Precipitation impacts of Atmospheric Rivers on the west coast of Southern South America

VALENZUELA R.; GARREAUD R. D.; VIALE M.

Reykjavík

Conferencia; 34th International Conference on Alpine Meteorology; 2017

University of Iceland

Similar to other mountainous west coast around the world, the west coast of southern South America (SA) is strongly affected by heavy orographic precipitation events that result from the landfalling Atmospheric Rivers (AR). An AR is a narrow and long corridor of enhanced moisture transport over the oceans that often, but not always, develops just ahead of midlatitude cold fronts. When frontal systems develops an AR over Southeastern Pacific ocean and it strikes the Andes mountains, orographic processes enhance precipitation over the upstream and the windward and immediate lee slopes sectors that occasionally produce floods, landslides, and at worst irrecoverable losses and fatalities. On the other hand, these heavy orographic precipitation events are a major contributor to water resources in the region, especially at the subtropical latitudes where the Andes are higher and melted snow irrigates the desert lands on both flanks of the range. Despite their importance, the SA region has a significant gap in the knowledge of AR phenomena and their impacts compared to North America and western Europa. In this study, we will discuss results from the quantification of how AR storms contribute to the annual total and extreme precipitation along the west coast of SA, between the southern tip of the continent and 30ºS, and across the Andes from the west coast (Chile) to the leeside (Argentina). The Integrated Water Vapor Transport (IVT), derived from Climate Forecast System Reanalysis (CFSR) data, is used for the AR identification over the period of 2001-2016; while daily and snow precipitation data networks of Chile and Argentina are used to quantify the impact of AR on precipitation over the region.