El Nino, water vapor, and the Global Positioning System

Abstract

The 1997-1998 El Nino had a profound impact on atmospheric circulation in the tropical Pacific and affected weather patterns world-wide. Precipitable water estimates from Global Positioning System (GPS) sites in the western tropical Pacific capture the sudden onset of large-scale subsidence, a phenomenon proposed as a possible mechanism driving the eventual decline of El Nino episodes. The atmospheric drying associated with this anomalous high-pressure ridge and the turnabout as the warm episode transitions into the subsequent La Nina are clearly visible in the GPS observations.