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Berkelhammer, M.
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Hu, J.
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Bailey, A.
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Noone, D. C.
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Still, C. J.
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Barnard, H.
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Gochis, D.
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Hsiao, G. S.
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Rahn, T.
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Turnipseed, A.
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| Abstract |
- The movement of moisture into, out-of, and within forest ecosystems is modulated
by feedbacks that stem from processes which couple plants, soil, and the atmosphere.
While an understanding of these processes has been gleaned from Eddy Covariance
techniques, the reliability of the method suffers at night because of weak turbulence.
During the summer of 2011, continuous profiles of the isotopic composition (i.e., δ¹⁸O
and δD) of water vapor and periodic measurements of soil, leaf, and precipitation pools
were measured in an open-canopy ponderosa pine forest in central Colorado to study
within-canopy nocturnal water cycling. The isotopic composition of the nocturnal water
vapor varies significantly based on the relative contributions of the three major
hydrological processes acting on the forest: dewfall, exchange of moisture between leaf
waters and canopy vapor, and periodic mixing between the canopy and background air.
Dewfall proved to be surprisingly common (~30% of the nights) and detectable on both
the surface and within the canopy through the isotopic measurements. While surface dew
could be observed using leaf wetness and soil moisture sensors, dew in the foliage was
only measurable through isotopic analysis of the vapor and often occurred even when no
dew accumulated on the surface. Nocturnal moisture cycling plays a critical role in water
availability in forest ecosystems through foliar absorption and transpiration, and
assessing these dynamics, as done here, is necessary for fully characterizing the
hydrological controls on terrestrial productivity.
- Keywords: dewfall, nocturnal boundary layer, water isotopes, forest hydrology
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| Citation |
- Berkelhammer, M., J. Hu, A. Bailey, D. C. Noone, C. J. Still, H. Barnard, D. Gochis, G. S. Hsiao, T. Rahn, and A. Turnipseed (2013), The nocturnal water cycle in an open-canopy forest, Journal of Geophysical Research: Atmospheres, 118, 10,225-10,242. doi:10.1002/jgrd.50701
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| Funding Statement (additional comments about funding) |
- C.J.S. acknowledges the support of a CIRES VisitingFaculty Fellowship. M.B., A.B., and D.N. were supported by the NationalScience Foundation Climate and Large Scale Dynamics program as partof an Faculty Early Career Development award (AGS-0955841). Supportfor David Gochis and Andrew Turnipseed was provided by the NationalScience Foundation through its support of NCAR and for NCAR technicalstaff through NSF grant EAR-0910831. The reported research waspartially supported by Los Alamos National Laboratory Directed Researchand Development Project entitled Isotopic Tracer for Climate RelevantSecondary Organic Aerosol (20090425ER).
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