HR: 11:20h
AN: B22B-05    [Abstracts]
TI: Hydrogen Isotope Compositions and Variability in Atmospheric Water Vapor, Evapotranspirated Water, and Hydrometeoric Water in Central New Mexico.
AU: * Strong, M
EM: mstrong@unm.edu
AF: University of New Mexico, Earth and Planetary Science Northrop Hall, Albuquerque, NM 87131 United States
AU: Sharp, Z
EM: zsharp@unm.edu
AF: University of New Mexico, Earth and Planetary Science Northrop Hall, Albuquerque, NM 87131 United States
AU: Gutzler, D
EM: gutzler@unm.edu
AF: University of New Mexico, Earth and Planetary Science Northrop Hall, Albuquerque, NM 87131 United States
AB: The hydrogen isotope composition (δD) of atmospheric water vapor has been semi-continuously measured since April 2005 at ground level and within the boundary layer over Albuquerque, New Mexico. Water vapor has been compared with concurrently collected hydrometeoric water, evaporated water from local soil, and transpired water from local plants. Ground-level air has been collected ~ 3 times a day while periodically (every 1 to 2 weeks) air has been collected in a light aircraft throughout and above the boundary layer at altitude intervals of ~1000 ft. Between April and August, ground-level water vapor δD ranges from -250‰ to -50‰. Variability of δD in ground-level water vapor occurs on at least three different time scales. A diurnal cycle of ~15‰ variation exists throughout much of the record. Larger variations, up to 100‰, occur on time scales that range from a few hours to a few days and are thought to be associated with weather fluctuations. A seasonal trend toward isotopically heavier summer values has also been observed, and the amplitude of short-term δD variations is smaller in summer. From April to June, the δD ranges from -250‰ to -50‰, with an average of ~ -150‰. For the months of July and August, δD ranges from -180‰ to -90‰ with an average of ~ -120‰. Precipitation, while infrequent, also becomes isotopically heavier and less variable in the summer. Dew point and δD are highly correlated during June ((Δ(δD)/(Δ(dew point °C)) = 7.7; r² = 0.76) but little to no correlation exists in April (r² = 0.11 ) and August (r² = 0.01). The δD values of transpired water from local Juniper and Sage are between ~ -20‰ to ~ -50‰; local evaporation from soil has δD between ~ -90‰ and ~ -110‰. Neither plants nor soil have shown significant changes in water vapor composition between June (dry season) and August (wet season). Our currently favored model for the observed ground-level variation in water vapor δD is one of a nearly constant contribution from plants and soil with a variable atmospheric contribution. Atmospheric δD exhibits pronounced variability associated with fluctuations in airmass trajectories and vertical motion as documented by local winds and the varying structure of the vertical boundary layer profiles.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 3307 Boundary layer processes
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
DE: 4870 Stable isotopes (0454, 1041)
SC: Biogeosciences [B]
MN: Fall Meeting 2005