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Oxidant Budgets of the Northern Hemisphere Troposphere Since 1950

1950 年以来北半球对流层的氧化剂收支

基本信息

批准号：
NE/M003248/1
负责人：
Claire Reeves
金额：
$ 31.87万
依托单位：
University of East Anglia
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM003248%2F1
关键词：
Oxidant Budgets Northern Hemisphere Troposphere

项目摘要

The hydroxyl radical (OH) is the dominant oxidizing agent in the troposphere, as such its concentration controls the abundances and lifetimes of most atmospheric pollutants, including the important greenhouse gas methane (CH4). Ozone (O3) is also an important oxidant and is itself a greenhouse gas. The concentrations of OH and O3 are interdependent, both being determined by a complex series of reactions involving CH4, carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOX = NO + NO2). As emissions of these compounds have changed substantially since pre-industrial times, the tropospheric budgets of OH and O3 will also have changed. However, there are large uncertainties associated with current understanding of these past changes and consequently very large uncertainties in projected future changes and associated climate impacts.Most of this uncertainty in past trends comes from lack of observations to constrain studies. Whilst there are a few direct observational data sets which indicate how O3 concentrations changed through the 20th century, there are none for OH. Direct observational data sets of CH4, NMVOCs, CO and NOX, extend, at best, from the 1980s. These time series can be extended backward in time through the analysis of air trapped in firn (unconsolidated snow). Whilst such historic time series have been available for CH4 for some time, only recently have they become available for CO and for some NMVOCs, in particular alkanes. Furthermore, we have also recently determined, from firn analysis, historic time series of alkyl nitrates. Alkyl nitrates are products of the chemistry involving NOX and as such can be used as a diagnostic of the changes in NOX. These new (and in the case of the alkyl nitrates, unique), historic time series provide an exciting opportunity to investigate the changing OH and O3 budgets of the northern hemisphere troposphere since 1950 with observational constraints never available before. Very interestingly, the simple analyses carried out on these time series to date suggest that substantial changes in the atmospheric chemistry have occurred. To exploit the full value of these time series a detailed study is required with a comprehensive chemistry-climate model. Here we propose the first such study.The outcomes of this study will be: 1) a better understanding of the impact of changing anthropogenic emissions on the OH and O3 budgets of the northern hemisphere troposphere; 2) an improved modelling capability with which to project future changes and better inform climate policy.This proposal brings together experts in firn air data interpretation with experts in chemistry-climate modelling. Both groups also have considerable expertise in organic (including alkyl) nitrate chemistry. This proposal specifically builds on past NERC funded work on the trends of alkanes and alkyl nitrates in firm air using simply relationships and models.

羟基自由基 (OH) 是对流层中的主要氧化剂，因此其浓度控制着大多数大气污染物的丰度和寿命，包括重要的温室气体甲烷 (CH4)。臭氧（O3）也是一种重要的氧化剂，本身就是一种温室气体。 OH 和 O3 的浓度是相互依赖的，两者都是由涉及 CH4、一氧化碳 (CO)、非甲烷挥发性有机化合物 (NMVOC) 和氮氧化物 (NOX = NO + NO2) 的一系列复杂反应决定的。由于这些化合物的排放自前工业时代以来已经发生了很大变化，OH 和 O3 的对流层预算也将发生变化。然而，目前对这些过去变化的理解存在很大的不确定性，因此预测的未来变化和相关的气候影响也存在很大的不确定性。过去趋势的不确定性大部分来自缺乏观察来限制研究。虽然有一些直接观测数据集表明 20 世纪 O3 浓度如何变化，但没有 OH 的数据集。 CH4、NMVOC、CO 和 NOX 的直接观测数据集最多可以从 20 世纪 80 年代开始。这些时间序列可以通过分析积雪（松散的雪）中的空气来向后延伸。虽然此类历史时间序列适用于 CH4 一段时间，但直到最近才适用于 CO 和一些 NMVOC（特别是烷烃）。此外，我们最近还通过分析确定了硝酸烷基酯的历史时间序列。硝酸烷基酯是涉及 NOX 的化学产物，因此可用作 NOX 变化的诊断。这些新的（对于硝酸烷基酯而言，是独一无二的）历史时间序列提供了一个令人兴奋的机会，可以利用前所未有的观测限制来研究 1950 年以来北半球对流层 OH 和 O3 预算的变化。非常有趣的是，迄今为止对这些时间序列进行的简单分析表明，大气化学已经发生了重大变化。为了充分利用这些时间序列的价值，需要使用全面的化学气候模型进行详细研究。在这里，我们提出第一个此类研究。这项研究的结果将是：1）更好地了解人为排放变化对北半球对流层 OH 和 O3 预算的影响； 2）改进的建模能力，可以预测未来的变化并更好地为气候政策提供信息。该提案汇集了空气数据解释专家和化学气候建模专家。两个小组在有机（包括烷基）硝酸盐化学方面也拥有丰富的专业知识。该提案特别建立在 NERC 过去资助的关于固定空气中烷烃和硝酸烷基酯趋势的工作的基础上，使用简单的关系和模型。