Variability of Precipitable Water Content in the Atacama Desert

The Atacama Desert in Northern Chile and southern parts of Peru is an area of hyper-aridity that is regarded as possibly the most arid desert in the world. Some scholars assert that its aridity is due to a rainshadow-like effect from the Andes mountains to the east. Others suggest the aridity is due to lower-troposphere stability from cold-water upwelling along the west coast of South America, which is driven by surface wind circulation around the southeast Pacific anticyclone. Another possible contributor to the hyper-aridity is subsidence of dry air from the descending branch of the local Hadley Cell circulation. In this study, we investigated variability of precipitable water vapor (PWV) content in the Atacama Desert. Specifically, in context of these aridity mechanisms, we searched for spatial relationships between PWV and sea surface temperature, mean sea level pressure, 2-m temperature, u and v components of 10-m winds, geopotential heights, and u and v components of the wind at 700 mb, 500 mb, and 300 mb. Time series of PWV at five sites in the region, Pico, Ollagüe, Antofagasta, San Pedro de Atacama, and the Atacama Pathfinder EXperiment (APEX) high-altitude telescope site, were correlated with monthly values of the aforementioned variables over a 38-year period (1979-2016). Data for all variables were taken from the ERA-Interim reanalysis. The five locations in the Atacama Desert selected for study vary in altitude and latitude, and exhibit seasonality in PWV, factors which were considered in this sensitivity analysis.