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Universität zu Köln. (2020)

Atmospheric water supply to the Atacama Desert from newly developed satellite remote sensing techniques and reanalysis

Böhm, Christoph

Titre : Atmospheric water supply to the Atacama Desert from newly developed satellite remote sensing techniques and reanalysis

Auteur : Böhm, Christoph

Université de soutenance : Universität zu Köln.

Grade : Doktorgrade 2020

Résumé partiel
Many facets of atmospheric water supply to the Atacama Desert are poorly understood. However, in-depth knowledge regarding water availability, moisture sources and the underlying mechanisms is required to investigate biological and geological processes and to identify potential mutual relationships. This thesis provides a comprehensive meteorological perspective on the atmospheric water supply to the Atacama Desert within the context of the recent climate. Spatial and temporal variability of moisture as well as their controlling mechanisms depend on the type of water supply, i.e. clouds, water vapor, fog or precipitation. To investigate the influence of the persistent stratocumulus cloud deck above the southeast Pacific on the desert region, a new cloud base height retrieval method is introduced. It allows to estimate the vertical position of these clouds, which can help to identify regions within the coastal desert that are potentially influenced by these clouds. A first application of this new method revealed a strong relation between stratocumulus properties and the isotopic composition of coastal Tillandsia populations. The proximity of the Atacama Desert to main acting zones of the El Niño-Southern Oscillation (ENSO) phenomenon and of the Pacific Decadal Oscillation (PDO) together with results from previous studies suggest that modes of climate variability have strong influence on the moisture supply to this region. As oscillating extreme phases of these climate modes have recurring periods on the order of a few years to decades, a long data record is needed to study their impact. Therefore, spatio-temporal variability of integrated water vapor (IWV) provided by a century-spanning reanalysis data set is studied in relation to ENSO and PDO. It is shown that the reanalysis represents IWV in a suitable manner to study its long-term variability. On a decadal time scale, the PDO revealed a stronger coupling to IWV compared to ENSO. According to a seasonal analysis, identified relationships between ENSO and IWV are in line with findings reported for precipitation in the northeastern Atacama. This suggests that IWV has the potential to serve as a proxy for precipitation. The ENSO signal is opposite for summer and winter season.

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