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，因此其浓度控制了大多数大气污染物的丰度和寿命，包括重要的温室气甲烷（CH4）。臭氧（O3）也是一种重要的氧化剂，本身就是温室气体。 OH和O3的浓度是相互依存的，既由涉及CH4，一氧化碳（CO），非甲烷挥发性有机化合物（NMVOC）和氮氧化物的复杂反应（NOX = nox =否 + NO2）确定。自从工业前时代以来，这些化合物的排放发生了很大变化，OH和O3的对流层预算也将发生变化。但是，与当前对这些过去的变化的理解有关，因此存在很大的不确定性，因此在预计的未来变化和相关的气候影响中非常不确定性。过去趋势的这种不确定性大多数来自缺乏观察结果来限制研究。尽管有一些直接的观察数据集表明O3浓度在20世纪如何变化，但没有一个oh。 CH4，NMVOCS，CO和NOX的直接观察数据集，最多从1980年代扩展。这些时间序列可以通过分析被困在FIRN中的空气（未固结的雪）来向后扩展。尽管此类历史性的时间序列已在CH4上有一段时间，但直到最近才适用于CO和一些NMVOC，尤其是Alkanes。此外，我们最近还从FIRN分析（烷基硝酸盐的历史时间序列）中确定。硝酸烷基是涉及NOX的化学产品的产物，因此可以用作NOX变化的诊断。这些新的（在烷基硝酸盐中，独特的）历史性时间序列提供了一个令人兴奋的机会，以调查自1950年以来北半球对流层的OH和O3预算不断变化的预算，而观察性约束从未有过。有趣的是，迄今为止在这些时间序列上进行的简单分析表明，大气化学的发生了实质性变化。为了利用这些时间序列的全部价值，需要使用综合化学气候模型进行详细研究。在这里，我们提出了第一个此类研究。这项研究的结果将是：1）更好地理解改变人为排放对北半球对流层OH和O3预算的影响； 2）改进的建模能力，可以通过该提案与化学气候 - 气候建模专家汇集FIRN空气数据解释的专家。两组在有机物（包括烷基）硝酸盐化学方面也具有相当大的专业知识。该提案专门建立在过去的NERC资助的工作基础上，利用简单的关系和模型在牢固的空气中烷基和硝酸烷基硝酸盐的趋势。