Research Article
Water vapor variability in the Atacama Desert during the 20th century

https://doi.org/10.1016/j.gloplacha.2020.103192Get rights and content
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Highlights

  • ERA-20C reanalysis is suitable to study integrated water vapor (IWV) variability across the Atacama Desert and the bordering southeast Pacific.

  • IWV variability reaches around 30% on a year to year basis.

  • On an inter-decadal time scale, PDO shows highest correlation with IWV compared to ENSO and local SST for the southern Atacama.

  • El Niño summers are dry while La Niña can feature both wetter and drier summers.

  • The northern part of the Atacama is more decoupled from the southeast Pacific than the southern part.

Abstract

This study focuses on integrated water vapor (IWV) which is the main source for precipitation, fog and dew formation in the Atacama Desert in northern Chile. In order to study its long-term variability, a consistent meteorological record is needed. Here, we utilize the European Centre for Medium-Range Weather Forecasts' reanalysis ERA-20C which provides IWV among other atmospheric variables over the course of the entire 20th century (1900–2010). In this two fold study, we first present a validation of ERA-20C IWV for the Atacama and the bordering southeast Pacific region. Comparisons to satellite observations, i.e. the Hamburg Ocean Atmosphere Parameters and Fluxes from Satellite data record and the Moderate Resolution Imaging Spectroradiometer measurements, for overlapping time periods prove the suitability of ERA-20C to study IWV variability. Assessment of the observation feedback in ERA-20C reveals a higher uncertainty for the beginning of the 20th century when fewer observations are assimilated. Nevertheless, departures of the assimilated observations do not show a systematic bias in space or time supporting suitability of ERA-20C for long-term investigations. In the second part of the study, we describe the IWV variability over the course of the 20th century. Deviations from the long-term mean greater than 30% are found on an inter-annual time scale over the continental Atacama. Furthermore, we investigate potential drivers of the IWV variability such as the Pacific Decadal Oscillation (PDO) and the El Niño Southern Oscillation (ENSO) phenomenon. The relationship between the local IWV and these large scale indices depends on region and season. For instance, during austral summer, La Niña conditions yield overall greater IWV variability in the Atacama allowing both drier and even more pronounced wetter extremes than El Niño conditions.

Keywords

Water cycle
Integrated water vapor
ERA-20C
Atacama
Hydrological cycle
Moisture transport

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