A Lagrangian perspective on stable water isotopes during the West African Monsoon

Diekmann, Christopher; Schneider, Mat­thias; Knippertz, Peter; Vries, Andries Jan de; Aemisegger, Franziska; Dahinden, Fabienne; Ertl, Benjamin; Khosrawi, Farahnaz; Wernli, Heini; Braesicke, Peter

doi:10.1002/essoar.10506628.1

Cited by 6 publications

(5 citation statements)

References 24 publications

(27 reference statements)

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“…Simulations were conducted at the Swiss National Supercomputing Centre (CSCS). The trajectory data can be accessed via the DOI: http://10.35097/469 (Diekmann & de Vries, 2021).…”

Section: Data Availability Statementmentioning

confidence: 99%

A Lagrangian Perspective on Stable Water Isotopes During the West African Monsoon

et al. 2021

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“…Simulations were conducted at the Swiss National Supercomputing Centre (CSCS). The trajectory data can be accessed via the DOI: http://10.35097/469 (Diekmann & de Vries, 2021).…”

Section: Data Availability Statementmentioning

confidence: 99%

A Lagrangian Perspective on Stable Water Isotopes During the West African Monsoon

et al. 2021

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“…Africa, on the other hand, with its complex dynamics and interaction between moist tropical and dry subtropical air masses and thus according effects on the isotopic composition seems to be generally an area that is difficult to simulate, both in terms of dynamics and isotopic processes (e.g. Diekmann et al, 2021b). Thus, this may explain why we find the lowest improvement in this region for the PREPBUFR experiment.…”

Section: Asiamentioning

confidence: 83%

Can the assimilation of water isotopologue observation improve the quality of tropical diabatic heating and precipitation?

Khosrawi

Toride

Yoshimura

et al. 2021

Preprint

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Abstract. The strong coupling between atmospheric circulation, moisture pathways and atmospheric diabatic heating is responsible for most climate feedback mechanisms and controls the evolution of severe weather events. However, diabatic heating rates obtained from current meteorological reanalysis show significant inconsistencies. Here, we theoretically assess with an Observation System Simulation Experiment (OSSE) the potential of the MUlti-platform remote Sensing of Isotopologues for investigating the Cycle of Atmospheric water (MUSICA) Infrared Atmospheric Sounding interferometer (IASI) mid-tropospheric water isotopologue data for constraining uncertainties in meteorological analysis fields. For this purpose, we use the Isotope-incorporated General Spectral Model (IsoGSM) together with a Local Ensemble Transform Kalman Filter (LETKF) and assimilate synthetic MUSICA IASI isotopologue observations. We perform two experiments consisting each of two ensemble simulation runs, one ensemble simulation where we assimilate conventional observations (temperature, humidity and wind profiles obtained from radiosonde and satellite data) and a second one where we assimilate additionally to the conventional observations the synthetic IASI isotopologue data. In the second experiment, we perform one ensemble simulation where only synthetic IASI isotopologue data are assimilated and another one where no observational data at all are assimilated. The first experiment serves to assess the impact of the IASI isotopologue data additional to the conventional observations and the second one to assess the direct impact of the IASI isotopologue data on the meteorological variables, especially on the heating rates and vertical velocity. The assessment is performed for the tropics in the latitude range from 10° S to 10° N. When the synthetic isotopologue data are additionally assimilated, we derive in both experiments lower Root-Mean Square Deviations (RMSDs) and improved skills with respect to meteorological variables (improvement by about 8–13 %). However, heating rates and vertical motion can only be improved throughout the troposphere when additionally to IASI δD conventional observations are assimilated. When only IASI δD is assimilated the improvement in vertical velocity and heating rate is minor (up to a few percent) and restricted to the mid-troposphere. Nevertheless, these assimilation experiments indicate that IASI isotopologue observations have the potential to reduce the uncertainties of diabatic heating rates and meteorological variables in the tropics and in consequence offer potential for improving meteorological analysis, weather forecasts and climatepredictions in the tropical regions.

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“…In summary, the combination of the aforementionedj processes, which are closely connected with the dominant transport pathways over West Africa, ultimately determine the prevailing signals in {H 2 O, D} pairs in the Sahelian mid-troposphere at a given time. A publication presenting the new Lagrangian process attribution procedure is realized in Diekmann et al (2021c). and Sect.…”

Section: Discussionmentioning

confidence: 99%

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

Diekmann

Schneider

Aemisegger

et al. 2021

Preprint

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Three-dimensional distributions of atmospheric moisture with high spatial and temporal variability arise from the complex interaction of the various branches in the hydrological cycle. By studying abundances of stable water isotopes, one can retrieve fundamental information about the physical processes acting in these branches. Differences in the molecular structure lead to characteristic responses of each water isotope to phase change processes, which reflects on characteristic ratios of water isotopes in different branches of the hydrological cycle.In this study, we use tropospheric distributions of H2O and HDO (denoted as &#948;D) to identify dominant processes in the hydrological cycle during the wet phase of the West African Monsoon in boreal summer. Here, large gradients in water vapor, strong convective activity and continental recycling lead to high variability of tropospheric moisture and its isotopic composition. This complexity makes a direct attribution of observed water vapor signals to underlying processes challenging.To address this challenge, we use remotely sensed {H2O, &#948;D} &#8211; pair data retrieved from spectra of the thermal infrared satellite sensor IASI, which are available daily and globally from October 2014 to June 2019. For an improved understanding of the IASI data, we add high-resolution model data from the regional isotope-enabled model COSMO-iso and generate Lagrangian backward trajectories for the Sahelian troposphere. This provides valuable insights into geometrical and moisture 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, &#948;D} &#8211; pairs for the Sahelian troposphere on interannual, seasonal and convective scales. We identify distinct effects on {H2O, &#948;D} &#8211; pairs of (1) synoptic-scale and boundary air mass mixing, (2) rain condensation during convection and (3) partial evaporation and isotope equilibration of rain drops during convection.This study reveals the potential of using MUSICA IASI {H2O, &#948;D} &#8211; pair data together with high-resolution modeling for investigating the tropospheric hydrological cycle. This approach is promising for understanding the relative importance of large-scale dynamics against microphysical phase transitions during convection on the tropical moisture distribution.

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A Lagrangian perspective on stable water isotopes during the West African Monsoon

Cited by 6 publications

References 24 publications

A Lagrangian Perspective on Stable Water Isotopes During the West African Monsoon

A Lagrangian Perspective on Stable Water Isotopes During the West African Monsoon

Can the assimilation of water isotopologue observation improve the quality of tropical diabatic heating and precipitation?

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

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