Unravelling the transport of moisture into the Saharan Air Layer using passive tracers and isotopes ...

• Main Authors: Dahinden, Fabienne, Aemisegger, Franziska, Wernli, Heini, Pfahl, Stephan
• Format: Text
• Language: unknown
• Published: Freie Universität Berlin 2023
• Subjects: atmospheric humidity; moisture sources; moisture transport; Saharan Air Layer; stable water isotopes; turbulent mixing; 500 Naturwissenschaften und Mathematik550 Geowissenschaften, Geologie551 Geologie, Hydrologie, Meteorologie; North Atlantic
• Online Access: https://dx.doi.org/10.17169/refubium-40375; https://refubium.fu-berlin.de/handle/fub188/40654

The subtropical free troposphere plays a critical role in the radiative balance of the Earth. However, the complex interactions controlling moisture in this sensitive region and, in particular, the relative importance of long-range transport compared to lower-tropospheric mixing, remain unclear. This study uses the regional COSMO model equipped with stable water isotopes and passive water tracers to quantify the contributions of different evaporative sources to the moisture and its stable isotope signals in the eastern subtropical North Atlantic free troposphere. In summer, this region is characterized by two alternating large-scale circulation regimes: (i) dry, isotopically depleted air from the upper-level extratropics, and (ii) humid, enriched air advected from Northern Africa within the Saharan Air Layer (SAL) consisting of a mixture of moisture of diverse origin (tropical and extratropical North Atlantic, Africa, Europe, the Mediterranean). This diversity of moisture sources in regime (ii) arises from ...