Development and Application of In-Situ Measurement of Water Vapor Isotopes For Hydrological And Ecological Research

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0229343Xuhui LeeThe proposal includes three tasks. In Task I, we will work with Campbell Scientific Inc. to design and build a TDL system for continuous and in-situ measurement of HDO and H218O isotope ratios in atmospheric water vapor. The instrument will be tested against a cold-trap method, used at Yale and elsewhere. In Task II, we will use the new TDL system to determine the isotopic ratio in water vapor evaporating from the earth's surface and exchanging with the lower atmosphere. The isotope flux ratio will be determined with the micrometeorological gradient-diffusion and eddy accumulation methods. The ability to determine the flux ratio accurately is essential in two fields of science: plant-water relationships and paleo-climate. In Task III, we will obtain and interpret continuous time series of stable water isotope ratio in surface air on time scales including boundary layer gusts, rain showers, the diurnal cycle, frontal cyclones and seasons. The advantage of our continuous time series is that we will be able to observe a variety of atmospheric processes operating on different time scales. We expect that the isotopic method will be extraordinarily sensitive to subtle changes in water vapor condensation and evaporation history of an airmassSuccessful completion of these tasks will open a new "window" on the hydrologic cycle, especially to processes involving phase changes of water. The project will also generate broader impact on the society by promoting partnership between the academia and a private industry and by contributing new instrumentation to the infrastructure for research in hydrology, ecology, meteorology and global change.