The Influence of Weather Systems on Interannual Isotopic Variability in a 10-Year High Resolution Simulation of Stable Water Isotopes over Europe
Abstract
Weather systems can strongly influence the isotopic composition of water vapor and precipitation. For example, passages of cold fronts often lead to a rapid decrease of δ2H and δ18O in precipitation, due to the change of air masses and progressive depletion during rainout. Such signals are also imprinted on long-term records of stable water isotopes in paleo-archives. However, apart from the positive correlation of the δ values with temperature, it is not yet perfectly clear how. To decipher these signals, a good understanding of the impact of weather systems on interannual isotopic variability is necessary, which is where numerical models can be helpful. We used the isotope-enabled version of the non-hydrostatic numerical weather prediction and climate model COSMO to perform a high-resolution simulation of stable water isotopes over Europe during the years 2002 - 2011, with the aim to identify the influence of cyclones and fronts on long-term isotopic variability. Both weather systems were detected in the model output using objective cyclone and front identification algorithms. Furthermore, the isotopes were traced along backward trajectories, which were started every 6 hours uniformly across the model domain. This allowed quantifying isotopic changes experienced by air parcels when they encountered a cyclone or a front. We found that most trajectories (especially those arriving over the Atlantic) have a lower δ2H and a higher deuterium excess, but a similar temperature, if they have passed through the core of a cyclone on their way, most likely due to depletion during rainout and below cloud evaporation of rain. This means that the occurrence of cyclones can lead to variations of δ2H that are not related to variations of temperature, which may have implications for the interpretation of isotope records in paleo-archives and the application of stable water isotopes as climate proxies.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMPP23E..08D
- Keywords:
-
- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSESDE: 1833 Hydroclimatology;
- HYDROLOGYDE: 4904 Atmospheric transport and circulation;
- PALEOCEANOGRAPHYDE: 4914 Continental climate records;
- PALEOCEANOGRAPHY