A perspective on time: loss frequencies, time scales and lifetimes

Prather, Michael J.; Holmes, Christopher D.

doi:10.1071/en13017

Cited by 4 publications

(2 citation statements)

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“…Our estimate of the lifetime sensitivity of N 2 O to its burden is s = À0.065 ± 0.010, where the ±0.010 is a 1 sigma uncertainty as it includes almost the entire range of models except for G2d. Thus, the feedback factor is ff = 0.94 ± 0.01, and the effective residence time of an N 2 O perturbation is 109 ± 10 years [e.g., Prather, 2007;Prather and Holmes, 2013]. Unfortunately, there is no semiempirical method to derive this sensitivity using MLS observations, but given the limited range for this value since first reported in 1998, we feel that ±15% 1 sigma uncertainty is a conservative choice.…”

Section: N 2 O Lifetimes and Chemical Feedbackmentioning

confidence: 99%

Measuring and modeling the lifetime of nitrous oxide including its variability

et al. 2015

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The lifetime of nitrous oxide, the third‐most‐important human‐emitted greenhouse gas, is based to date primarily on model studies or scaling to other gases. This work calculates a semiempirical lifetime based on Microwave Limb Sounder satellite measurements of stratospheric profiles of nitrous oxide, ozone, and temperature; laboratory cross‐section data for ozone and molecular oxygen plus kinetics for O(1D); the observed solar spectrum; and a simple radiative transfer model. The result is 116 ± 9 years. The observed monthly‐to‐biennial variations in lifetime and tropical abundance are well matched by four independent chemistry‐transport models driven by reanalysis meteorological fields for the period of observation (2005–2010), but all these models overestimate the lifetime due to lower abundances in the critical loss region near 32 km in the tropics. These models plus a chemistry‐climate model agree on the nitrous oxide feedback factor on its own lifetime of 0.94 ± 0.01, giving N2O perturbations an effective residence time of 109 years. Combining this new empirical lifetime with model estimates of residence time and preindustrial lifetime (123 years) adjusts our best estimates of the human‐natural balance of emissions today and improves the accuracy of projected nitrous oxide increases over this century.

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Section: N 2 O Lifetimes and Chemical Feedbackmentioning

confidence: 99%

Measuring and modeling the lifetime of nitrous oxide including its variability

et al. 2015

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“…One reason for separating P and L in this 215 way is to think of P as independent of O3 and L as being linearly proportional. Unfortunately, while the P reactions (2) have no obvious O3 terms, both these reactions and the OH and HO2 abundances in reactions (3) depend indirectly on O3; and thus with a true linearization of P-L, the lifetime of O3 is much shorter than inferred from L (Prather and Holmes, 2013). A similar chemical feedback with opposite sign occurs for CH4 whereby the lifetime of a CH4 addition is 220 longer than inferred from the linear relationship of reaction (1) (Prather, 1996).…”

Section: O3 + Oh  O2 + Ho2mentioning

confidence: 99%

Global Atmospheric Chemistry – Which Air Matters

Prather¹,

Zhu²,

Flynn³

et al. 2017

Preprint

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Abstract. An approach for analysis and modeling of global atmospheric chemistry is developed for application to measurements that provide a tropospheric climatology of those heterogeneously distributed, reactive species that control the loss of methane and the production and loss of ozone. We identify key species (e.g., O3, NOx, HNO3, HNO4, C2H3NO5, H2O, HOOH, CH3OOH, HCHO, CO, CH4, C2H6, acetaldehyde, acetone), and presume that they can be measured simultaneously in air parcels on the scale of a few km horizontally and a few tenths vertically. Six global models have prepared such climatologies (at model resolution) for August with emphasis on the vast central Pacific and Atlantic Ocean basins. We show clear differences in model generated reactivities as well as species covariances that could readily be discriminated with an unbiased climatology. A primary tool is comparison of multi-dimensional probability densities of key species weighted by frequency of occurrence as well as by the reactivity of the parcels with respect to methane and ozone. The reactivity-weighted probabilities tell us which parcels matter in this case. Testing 100-km scale models with 2-km measurements using these tools also addresses a core question about model resolution and whether fine-scale atmospheric structures matter to the overall ozone and methane budget. A new method enabling these six global chemistry-climate models to ingest an externally-sourced climatology and then compute air parcel reactivity is demonstrated. Such an observed climatology is anticipated from the NASA Atmospheric Tomography (ATom) aircraft mission (2015&#8211;2020), measuring the key species, executing profiles over the Pacific and Atlantic Ocean basins. This work is a core part of the design of ATom.

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100 Years of Progress in Gas-Phase Atmospheric Chemistry Research

Wallington

Seinfeld

Barker

2019

Meteorological Monographs

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Remarkable progress has occurred over the last 100 years in our understanding of atmospheric chemical composition, stratospheric and tropospheric chemistry, urban air pollution, acid rain, and the formation of airborne particles from gas-phase chemistry. Much of this progress was associated with the developing understanding of the formation and role of ozone and of the oxides of nitrogen, NO and NO2, in the stratosphere and troposphere. The chemistry of the stratosphere, emerging from the pioneering work of Chapman in 1931, was followed by the discovery of catalytic ozone cycles, ozone destruction by chlorofluorocarbons, and the polar ozone holes, work honored by the 1995 Nobel Prize in Chemistry awarded to Crutzen, Rowland, and Molina. Foundations for the modern understanding of tropospheric chemistry were laid in the 1950s and 1960s, stimulated by the eye-stinging smog in Los Angeles. The importance of the hydroxyl (OH) radical and its relationship to the oxides of nitrogen (NO and NO2) emerged. The chemical processes leading to acid rain were elucidated. The atmosphere contains an immense number of gas-phase organic compounds, a result of emissions from plants and animals, natural and anthropogenic combustion processes, emissions from oceans, and from the atmospheric oxidation of organics emitted into the atmosphere. Organic atmospheric particulate matter arises largely as gas-phase organic compounds undergo oxidation to yield low-volatility products that condense into the particle phase. A hundred years ago, quantitative theories of chemical reaction rates were nonexistent. Today, comprehensive computer codes are available for performing detailed calculations of chemical reaction rates and mechanisms for atmospheric reactions. Understanding the future role of atmospheric chemistry in climate change and, in turn, the impact of climate change on atmospheric chemistry, will be critical to developing effective policies to protect the planet.

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A perspective on time: loss frequencies, time scales and lifetimes

Cited by 4 publications

References 48 publications

Measuring and modeling the lifetime of nitrous oxide including its variability

Measuring and modeling the lifetime of nitrous oxide including its variability

Global Atmospheric Chemistry – Which Air Matters

100 Years of Progress in Gas-Phase Atmospheric Chemistry Research

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