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| Titel |
Lagrangian investigation of high-frequency variations in stable isotope composition of atmospheric boundary layer water vapour |
| VerfasserIn |
F. Aemisegger, S. Pfahl, H. Sodemann, I. Lehner, H. Wernli |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068556
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| Zusammenfassung |
| Process-based investigations of the atmospheric water cycle using stable water isotopes have
become possible lately at the time scales of significant weather events using novel laser
spectroscopic measurement techniques. In this work, we analyse 6 months of stable water
isotope measurements performed in the boundary layer water vapour at a prealpine
measurement site at high temporal resolution (1 hour). Since the water isotopic composition
of an air parcel is determined by the integrated history of phase changes and mixing processes
from evaporation to the point of measurement, we adopt a Lagrangian perspective to
interpret the data. We apply a moisture source and source condition identification
algorithm from 3D kinematic backward trajectories based on atmospheric analysis
data. This technique gives us a good estimate of the properties of the advected air
masses. The moisture source properties of these air masses can be used to predict
the deuterium excess (d = δ2H-8δ18O) at the measurement site. Generally good
correlations are found between the deuterium excess at the measurement site and moisture
source relative humidity and temperature. However, especially in summer, local
processes linked to turbulent mixing in the boundary layer and evapotranspiration at the
local scale are very important and not well represented by the chosen Lagrangian
moisture source identification method. A simple box model approach has thus been
chosen to better characterise these local effects and to complement the Lagrangian
perspective of large-scale moisture advection. The relative importance of the local
dynamics of the water cycle in contrast to remote phase changes can thus be quantified. |
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