Aemisegger, F.

Braesicke, P.

Dahinden, F.

Diekmann, C.

Ertl, B.

Hase, F.

Khosrawi, F.

Knippertz, P.

Pfahl, S.

Schneider, M.

Vries, A. de

Wernli, H.

English

KITopen

EGU21-10121https://doi.org/10.5194/egusphere-egu21-10121EGU General Assembly 2021© Author(s) 2022. This work is distributed underthe Creative Commons Attribution 4.0 License.Analysis of stable water isotopes in tropospheric moisture duringthe West African MonsoonChristopher Diekmann1, Matthias Schneider1, Franziska Aemisegger3, Fabienne Dahinden3,Benjamin Ertl2, Frank Hase1, Farahnaz Khosrawi1, Stephan Pfahl4, Andries de Vries3, Heini Wernli3,Peter Knippertz1, and Peter Braesicke11Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, Germany2Steinbuch Centre for Computing, Karlsruhe Institute of Technology, Karlsruhe, Germany3Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland4Institute of Meteorology, FU Berlin, Berlin, GermanyThree-dimensional distributions of atmospheric moisture with high spatial and temporal variabilityarise from the complex interaction of the various branches in the hydrological cycle. By studyingabundances of stable water isotopes, one can retrieve fundamental information about thephysical processes acting in these branches. Differences in the molecular structure lead tocharacteristic responses of each water isotope to phase change processes, which reflects oncharacteristic ratios of water isotopes in different branches of the hydrological cycle.In this study, we use tropospheric distributions of H2O and HDO (denoted as δD) to identifydominant processes in the hydrological cycle during the wet phase of the West African Monsoon inboreal summer. Here, large gradients in water vapor, strong convective activity and continentalrecycling lead to high variability of tropospheric moisture and its isotopic composition. Thiscomplexity makes a direct attribution of observed water vapor signals to underlying processeschallenging.To address this challenge, we use remotely sensed {H2O, δD} – pair data retrieved from spectra ofthe thermal infrared satellite sensor IASI, which are available daily and globally from October 2014to June 2019. For an improved understanding of the IASI data, we add high-resolution model datafrom the regional isotope-enabled model COSMO-iso and generate Lagrangian backwardtrajectories for the Sahelian troposphere. This provides valuable insights into geometrical andmoisture pathways along the history of Sahelian air masses that were observed from IASI. Further,after applying a retrieval simulator on the COSMO-iso data, we can conduct direct satellite-to-model comparisons.By drawing these datasets together, we document and analyze the characteristic variability of the{H2O, δD} – pairs for the Sahelian troposphere on interannual, seasonal and convective scales. Weidentify distinct effects on {H2O, δD} – pairs of (1) synoptic-scale and boundary air mass mixing, (2)rain condensation during convection and (3) partial evaporation and isotope equilibration of raindrops during convection.This study reveals the potential of using MUSICA IASI {H2O, δD} – pair data together with high-resolution modeling for investigating the tropospheric hydrological cycle. This approach ispromising for understanding the relative importance of large-scale dynamics againstmicrophysical phase transitions during convection on the tropical moisture distribution.Powered by TCPDF (www.tcpdf.org)

Analysis of stable water isotopes in tropospheric moisture during the West African Monsoon

https://publikationen.bibliothek.kit.edu/1000142017/141036189

Analysis of stable water isotopes in tropospheric moisture during the West African Monsoon

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