In-situ stable isotope observations of local and regional water vapour contributions in an open grassland
Abstract
To better constrain land atmosphere exchange of water vapour and understand the controlling factors for surface water vapour isotopic composition, an extensive two-week field campaign was conducted at the University of New South Wales Baldry hydrological observatory. The Baldry observatory is a 260 ha area of central New South Wales, Australia covered by native grasses and also containing two 50 acre parcels of Eucalyptus plantations. The site is equipped with flux monitoring equipment (e.g., eddy covariance, large aperture-scintillometers) and meteorological towers within forested areas and on the grassland. Two laser-based stable isotope instruments (WS-CRDS and OA-ICOS) were used to monitor the isotopic composition of surface layer atmospheric water vapour alongside flux and meteorological observations within the grassland area. The OA-ICOS system was used to directly determine the isotopic composition of the evapotranspiration flux using chamber-based measurements from bare and vegetated soil plots. Samples were also collected to determine the isotopic composition of leaf and soil waters and to provide an additional constraint of end member values for evaporation and transpiration. To investigate the dynamic between local sources and atmospheric processes (i.e. advection and mixing) the chamber measurements were compared to the water vapour stable isotopes measured from 5 heights (0, 0.5, 2.5, 5 and 7 m) on a meteorological tower (WS-CRDS). To further constrain the influence of atmospheric mixing on the stable isotope measurements, radon measurements were monitored at 2 m and a ground based LIDAR instrument was employed to continuously monitor boundary layer height. Initial results indicate local water vapour fluxes and atmospheric mixing both played a large role in the observed diurnal variations in the surface humidity and its isotopic composition.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.B31E0367S
- Keywords:
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- 0315 ATMOSPHERIC COMPOSITION AND STRUCTURE / Biosphere/atmosphere interactions;
- 0394 ATMOSPHERIC COMPOSITION AND STRUCTURE / Instruments and techniques;
- 0426 BIOGEOSCIENCES / Biosphere/atmosphere interactions;
- 0452 BIOGEOSCIENCES / Instruments and techniques