An Improved Understanding of Water Isotope Fractionation in Atmospheric Vapor and Its Source

该研究项目旨在建立一个优质的水同位素研究站，提供高质量、频繁和不间断的大气水汽同位素(2H和18O)测量，以研究水汽同位素分馏及其在生态系统-大气水和二氧化碳交换中的应用。这项研究建立在目前对植被-大气相互作用影响下的水汽同位素分馏的理解基础上。该项目将评估水球同位素模型中的一些关键假设，确定关键的分馏过程，并开发机械算法，以解决在水文和碳循环研究中掩盖氢和氧同位素示踪剂潜力的问题。这项研究的目标是：量化雨滴下降过程中云下蒸发的程度及其对森林空气中水汽同位素变化的影响；确定这种水的循环如何影响大气水分和降水；评估以植物为基础的替代物作为地面空气中大气水汽的积分器；在水球同位素模型中提供伴随地表蒸散的同位素分馏机制算法。研究成果补充了一些网络的合成活动，包括生物圈-大气稳定同位素网络(BERAGE)、生物圈和大气中的水分同位素(MIBA)、ameriFlux和北美碳计划(NACP)站点临时合成。将在课程中增加新的课程，以促进在生物地球科学研究中使用稳定同位素比率测量，以确保学生掌握广泛的技术技能，鼓励本科生参与实验室研究，并提高公众对气候变化的生态水文后果的认识。

This research project aims to establish a premium water isotope research station with high quality, frequent and uninterrupted atmospheric vapor isotope (2H and 18O) measurements to investigate vapor isotope fractionation and its applications on ecosystem-atmosphere water and CO2 exchange. The research builds upon current understanding of water vapor isotopic fractionation under the influence of vegetation-atmosphere interaction. This project will evaluate a number of critical assumptions in hydrospheric isotope models, identify key fractionation processes, and develop mechanistic algorithms to address caveats that mask the potential of hydrogen and oxygen isotope tracers in hydrological and carbon cycle research. Objectives of the research are to: quantify the extent of below-cloud evaporation during the descent of raindrops and its effects on the vapor isotope variation in forest air; determine how this recycling of water affects atmospheric moisture and precipitation; evaluate plant-based proxy as an integrator of atmospheric vapor in surface air; provide mechanistic algorithms of isotope fractionation that accompanies surface evapotranspiration in hydrospheric isotope models.Products of the research complement synthesis activities for a number of networks, including Biosphere-Atmosphere Stable Isotope Network (BASIN), Moisture Isotopes in the Biosphere and Atmosphere (MIBA), AmeriFlux, and North American Carbon Program (NACP) site interim synthesis. New courses will be added to the curriculum to promote the use of stable isotope ratio measurements in biogeoscience research, in order to ensure a breadth of technological skills in students, encourage undergraduate student participation in laboratory research, and increase public awareness of the eco-hydrological consequences of climate change.