Isotopic Composition of Nitrous Oxide and Carbon Dioxide

该项目解决了一氧化二氮和二氧化碳的全球预算，这是地球大气中的两种主要温室气体。该项目将涉及对引起同位素分馏的微观分子过程进行建模和对大气进行建模，重点是对提出的与质量无关的分馏机制进行定量评估，并解释最近发现的一氧化二氮的季节性循环。研究将集中在两种目标化合物的主要同位素的光解和动力学速率系数计算、数据分析和大气建模上，这两种目标化合物具有主要由中大气分馏过程驱动的大而独特的同位素特征。对大气气体的多同位素分馏模式的了解，对它们的化学、传输和来源提供了强有力的约束。加州理工学院/喷气推进实验室的二维和NCAR三维MATCH（大气输送和化学模型）的等熵版本的组合将用于解释NOAA CMDL数据、AGAGE（高级全球大气气体实验）数据、平流层数据和其他可用的同位素数据。此外，反演方法将用于约束一氧化二氮的大陆和海洋来源。另一个目标是将最近用于氧化亚氮的相同技术应用于二氧化碳，从而对同位素分馏及其通过输运过程稀释的机制有一个基本的了解。二氧化碳的同位素分馏可以提供关于平流层上层和中间层的化学和输送过程以及地表生物圈过程的独特信息。结合加州理工学院/喷气推进实验室的二维和NCAR的三维WACCM（全大气群落气候模式）模式，将用于模拟二氧化碳从地表到中间层的同位素组成。这些研究工作将有助于培养研究生、博士后和本科生。

This project addresses the global budgets of nitrous oxide and carbon dioxide, which are two of the principal greenhouse gases in the terrestrial atmosphere. The project will involve modeling of microscopic molecular processes responsible for causing isotopic fractionation and atmospheric modeling, with emphasis on a quantitative evaluation of the mechanisms proposed for mass-independent fractionation and the interpretation of the recently discovered seasonal cycle of nitrous oxide. The research will focus on photolysis and kinetic rate coefficient computations, data analysis and atmospheric modeling of the principal isotopologues of the two target compounds, which have large and distinctive isotopic signatures driven primarily by fractionation processes in the middle atmosphere. An understanding of the multi-isotope fractionation patterns of atmospheric gases provides powerful constraints on their chemistry, transport and sources. A combination of the Caltech/JPL 2-dimensional and an isentropic version of the NCAR 3-dimensional MATCH (Model of Atmospheric Transport and Chemistry) will be used to explain the NOAA CMDL data, AGAGE (Advanced Global Atmospheric Gases Experiment) data, stratospheric data, and other available isotopic data. Additionally, inversion methods will be used to constrain the continental and oceanic sources of nitrous oxide.Another goal is to apply to carbon dioxide the same techniques that have recently been developed for nitrous oxide, to arrive at a fundamental understanding of the mechanisms for the isotopic fractionation and its dilution by transport processes. The isotopic fractionation of carbon dioxide may provide unique information on chemical and transport processes in the upper stratosphere and mesosphere, as well biospheric processes at the surface. A combination of the Caltech/JPL 2-dimensional and the NCAR 3-dimensional WACCM (Whole Atmosphere Community Climate Model) models will be used to model the isotopic composition of carbon dioxide from the surface to the mesosphere.The research efforts will contribute to the training of graduate students, postdoctoral fellows and undergraduates.