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Synoptic-scale controls of fog and low-cloud variability in the Namib Desert

Andersen, Hendrik ORCID iD icon 1,2; Cermak, Jan ORCID iD icon 1,2; Fuchs, Julia 1,2; Knippertz, Peter ORCID iD icon 2; Gaetani, Marco; Quinting, Julian ORCID iD icon 2; Sippel, Sebastian; Vogt, Roland
1 Institut für Photogrammetrie und Fernerkundung (IPF), Karlsruher Institut für Technologie (KIT)
2 Institut für Meteorologie und Klimaforschung (IMK), Karlsruher Institut für Technologie (KIT)

Abstract (englisch):

Fog is a defining characteristic of the climate of the Namib Desert, and its water and nutrient input are important for local ecosystems. In part due to sparse observation data, the local mechanisms that lead to fog occurrence in the Namib are not yet fully understood, and to date, potential synoptic-scale controls have not been investigated. In this study, a recently established 14-year data set of satellite observations of fog and low clouds in the central Namib is analyzed in conjunction with reanalysis data in order to identify synoptic-scale patterns associated with fog and low-cloud variability in the central Namib during two seasons with different spatial fog occurrence patterns. It is found that during both seasons, mean sea level pressure and geopotential height at 500 hPa differ markedly between fog/low-cloud and clear days, with patterns indicating the presence of synoptic-scale disturbances on fog and low-cloud days. These regularly occurring disturbances increase the probability of fog and low-cloud occurrence in the central Namib in two main ways: (1) an anomalously dry free troposphere in the coastal region of the Namib leads to stronger longwave cooling of the marine boundary layer, increasing low-cloud cover, especially over the ocean where the anomaly is strongest; (2) local wind systems are modulated, leading to an onshore anomaly of marine boundary-layer air masses. ... mehr

Verlagsausgabe §
DOI: 10.5445/IR/1000117856
DOI: 10.5194/acp-20-3415-2020
Zitationen: 17
Zitationen: 20
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung – Atmosphärische Spurenstoffe und Fernerkundung (IMK-ASF)
Institut für Meteorologie und Klimaforschung Troposphärenforschung (IMKTRO)
Institut für Photogrammetrie und Fernerkundung (IPF)
KIT-Zentrum Klima und Umwelt (ZKU)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 1680-7324
KITopen-ID: 1000117856
HGF-Programm 12.01.02 (POF III, LK 01) Proc.res.f.multisc.predictab.of weather
Weitere HGF-Programme 12.11.26 (POF IV, LK 01) Aerosol-Cloud-Climate-Interaction
Erschienen in Atmospheric chemistry and physics
Verlag European Geosciences Union (EGU)
Band 20
Heft 6
Seiten 3415–3438
Bemerkung zur Veröffentlichung Gefördert durch den KIT-Publikationsfonds
Vorab online veröffentlicht am 24.03.2020
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