Collaborative Research: Testing Controls on Source, Sink, and Lifetime of Atmospheric Water with Numerical Tags and Stable Isotope Ratios

合作研究：利用数值标签和稳定同位素比率测试对大气水源、汇和寿命的控制

• 批准号: 2309269
• 负责人: Richard Fiorella
• 金额: $ 31.1万
• 依托单位: New Mexico Consortium
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-01-15 至 2024-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309269&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Controls; Source

H2O is instantly recognizable as the chemical formula for water, but this simple formula masks the fact that not all hydrogen atoms are alike. A small fraction of the water on earth could be more accurately called HDO, where D stands for deuterium, the heavier hydrogen isotope in which the nucleus contains a neutron as well as a proton. Likewise, some water molecules contain 18O, an isotope of oxygen which is heavier than ordinary oxygen by the addition of two neutrons. These heavier forms of water share a subtle but important difference from ordinary H2O: they evaporate more sluggishly and condense more readily, preferring the solid and liquid phases to the vapor phase. When water evaporates from the land or ocean surface the vapor is slightly depleted of the heavier isotopes, and each time rain falls from a cloud the water vapor remaining in the atmosphere is slightly lighter than the water that rained out. The removal of heavier isotopes by precipitation suggests that the abundances of heavier isotopes in water vapor and precipitated water contain important clues for understanding the hydrological cycle and its connections to environmental conditions. Results of research in this area are promising but they are complicated by the numerous factors that can influence isotopic composition. Among these are the temperature at the location where the precipitation occurred, the height of the cloud that produced the precipitation, the relative humidity over the ocean where the water vapor evaporated, and the evaporation of lighter isotopes from raindrops as they fall through dry air. Moreover, much of the research on water isotopes is based on correlations between isotopic composition and variables relevant to physical mechanisms (temperature in the region of rainout, for instance). These correlations can be quite informative but correlations by themselves cannot definitively establish causality.Work under this award seeks to establish direct, causal relationships between the physical mechanisms relevant to isotopic composition and the actual composition of water vapor and precipitated water. The research is conducted using a model, the Community Earth System Model (CESM), in which the mechanisms and their influence on isotopic composition are known exactly. CESM is already equipped to simulate the physical processes that determine the ratio of heavier to lighter isotopes, and it also tracks the isotopic composition of water vapor as it circulates in the simulated atmosphere. This project develops a new "water tagging" capability which allows simulated water vapor to record information about conditions under which it evaporated, for instance where and when it evaporated and whether it was processed through clouds. This information is also transferred to the precipitation produced when water vapor condenses. The tag information can be directly compared to isotopic composition, allowing the influence of the physical conditions and processes represented by the tags to be directly assessed. Some simulations use a data assimilation system (known as DART) to ensure that the simulated climate and circulation accurately represent their real-world counterparts. Additional work uses a one-dimensional energy balance model, which provides a reduced-complexity setting to develop new ideas and test hypotheses.The work has scientific broader impacts due to the widespread use of water isotopes as a window on the functioning of climate and the hydrological cycle. For instance isotope ratios in glacial ice cores have been used to estimate temperature differences between ice ages and interglacial warm periods, thus providing a valuable point of reference for understanding current climate change. The water tagging algorithms developed here will be made available to the worldwide user community of CESM, providing users with a powerful tool for the interpretation of isotope data and its application to a variety of research questions.In addition, researchers supported under this award conduct educational outreach through a program focused on the Decker Lake Youth Center, a facility housing post-conviction youth in the Salt Lake Valley. The outreach involves ozone bioindicator gardens which demonstrate the hazards of ozone pollution, a common problem in the Salt Lake Valley. Educational opportunities in correctional facilities have been shown to reduce recidivism.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

H2O立即被识别为水的化学公式，但是这种简单的公式掩盖了并非所有氢原子都是相似的事实。 地球上的一小部分水可以更准确地称为HDO，D代表氘代表氘，核的较重的氢同位素，其中核中包含一个中子和质子。 同样，某些水分子含有18O，这是一种氧的同位素，通过添加两个中子比普通氧气重。 这些较重形式的水与普通H2O具有微妙但重要的区别：它们更慢，更容易凝结，更喜欢固体和液相相对于蒸气相。 当水从陆地或海洋表面蒸发时，蒸气会稍微耗尽较重的同位素，每次雨水从云中掉落时，大气中的水蒸气仍比下雨的水略轻一些。 通过降水清除较重的同位素表明，水蒸气和沉淀水中较重的同位素的丰度包含重要线索，以了解水文循环及其与环境条件的连接。该领域的研究结果是有希望的，但它们会因影响同位素组成的众多因素而变得复杂。 其中包括在降水量发生的位置的温度，产生降水量的云高度，水蒸气蒸发的海洋的相对湿度以及在干燥空气中掉落雨滴的较轻同位素的蒸发。 此外，对水同位素的许多研究都是基于同位素组成与与物理机制相关的变量（例如，Rainout地区温度）之间的相关性。 这些相关性可能是非常有用的，但相关性本身不能确定建立因果关系。该奖项下的工作旨在建立与同位素组成相关的物理机制与水蒸气和沉淀水的实际组成之间的直接因果关系。 这项研究是使用模型，即社区地球系统模型（CESM）进行的，其中的机理及其对同位素组合物的影响恰好是已知的。 CESM已经有能力模拟确定较重与较轻同位素比率的物理过程，并且还跟踪水蒸气在模拟气氛中循环时的同位素组成。 该项目开发了一种新的“水标记”功能，该功能允许模拟水蒸气记录有关其蒸发的条件的信息，例如蒸发的位置和时间以及是否通过云处理。 当水蒸气凝结时，该信息还将转移到产生的降水中。 可以将标签信息直接与同位素组合物进行比较，从而可以直接评估标签所代表的物理条件和过程的影响。一些模拟使用数据同化系统（称为DART）来确保模拟的气候和循环准确代表其现实世界中的对应物。 其他工作使用一维能量平衡模型，该模型提供了降低的复杂性设置来开发新的想法和测试假设。由于广泛使用水同位素作为气候和水文循环功能的窗口，这项工作具有更广泛的影响。 例如，冰川冰芯中的同位素比已被用来估计冰河时代和冰川间温暖时期之间的温度差异，从而为理解当前的气候变化提供了宝贵的参考点。此处开发的水标记算法将提供给CESM的全球用户社区，为用户提供了一种强大的工具，用于解释同位素数据及其在各种研究问题上的应用。此外，此外，根据该奖项进行的研究人员通过该奖项的教育宣传，该计划通过针对甲板湖青年中心（甲板湖青年中心），设施后的盐湖山谷（Salt Lake Valley）的甲板湖青年中心（Salt Lake Lakeley）的甲板湖青年中心（Salt Lake Lakeley Inthal Salt Lakeley）进行了研究。 外展活动涉及臭氧生物指导花园，这些花园表现出臭氧污染的危害，这是盐湖谷的常见问题。惩教设施中的教育机会已被证明可以减少累犯。该奖项反映了NSF的法定使命，并被认为是值得通过基金会的知识分子优点和更广泛影响的评论标准来评估值得支持的。