Abstract

Interannual variability of precipitation in Central Chile has long been associated with changes in the dry atmospheric dynamics of the Southern Pacific. This is due to the interaction between the extratropical storm track and the polar anticyclonic circulations established by the Pacific South American (PSA) teleconnection mode, which results from changes in tropical convection. Here, we show that an enhanced subtropical moisture transport during the warm ENSO phase leads to an increase in the frequency of atmospheric rivers, larger values of precipitable water, and heightened zonal integrated water vapor transport. This occurs in a region of the Southern Pacific situated between the tropical high and the subtropical low of the PSA mode. These increases in zonal water vapor transport result in greater precipitation and moister, long-lived atmospheric rivers making landfall in Central Chile. Plain Language Summary Changes in the amount of rain Central Chile gets from year to year is often related to how the atmosphere behaves over the Southern Pacific Ocean. Specifically, it is connected to the interaction between storm tracks and certain wind patterns that respond to changes in the amount of rainfall in tropical areas. Our research shows that during the warm part of a natural climate cycle known as ENSO, there is more moisture transported from subtropical areas. This leads to more occurrences of what are known as atmospheric rivers, which are essentially large streams of water vapor in the sky. It also leads to a greater amount of water vapor in the air and more of this vapor being moved across the Pacific. These changes mean that there is more rain and atmospheric rivers, which carry a lot of moisture and stick around for a long time, affecting Central Chile. So our work is helping to reveal how changes in the rainfall in tropical areas can influence the amount of rain that falls in distant places like Central Chile.