Global scale variability of the mineral dust long-wave refractive index: a new dataset of in situ measurements for climate modeling and remote sensing Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1901-2017 9 February 2017 Modeling the interaction of dust with long-wave (LW) radiation is still a challenge due to the scarcity of information on their refractive index. In this paper, we present a unique dataset of dust refractive indices obtained from in situ measurements in a large smog chamber. Our results show that the dust LW refractive index varies strongly from source to source due to particle composition changes. We recommend taking this variability into account in climate and remote sensing applications. Read more
Halogen chemistry reduces tropospheric O3 radiative forcing Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1557-2017 31 January 2017 We model pre-industrial to present day changes using the GEOS-Chem global chemical transport model with halogens (Cl, Br, I). The model better captures pre-industrial O3observations with halogens included. Halogens buffer the tropospheric forcing of O3(RFTO[~3~]) from pre-industrial to present day, reducing RFTO[~3~]by 0.087 Wm−2. This reduction is greater than that from halogens on stratospheric O3(−0.05 Wm−2). This suggests that models that do not include halogens will overestimate RFTO[~3~]by ~ 25%. Read more
Decadal changes in global surface NOx emissions from multi-constituent satellite data assimilation Atmospheric Chemistry and Physics DOI 10.5194/acp-17-807-2017 27 January 2017 Global surface emissions of nitrogen oxides (NOx) over a 10-year period (2005–2014) are estimated from assimilation of multiple satellite datasets. We present detailed distributions of the estimated NOxemission distributions for all major regions, the diurnal, seasonal, and decadal variability. The estimated emissions show a positive trend over India, China, and the Middle East, and a negative trend over the United States, southern Africa, and western Europe. Read more
Determination of the atmospheric lifetime and global warming potential of sulfur hexafluoride using a three-dimensional model Atmospheric Chemistry and Physics DOI 10.5194/acp-17-883-2017 20 January 2017 Sulfur hexafluoride (SF6) is a very potent greenhouse gas, which is present in the atmosphere only through its industrial use, for example as an electrical insulator. To estimate accurately the impact of SF6emissions on climate we need to know how long it persists in the atmosphere before being removed. Previous estimates of the SF6lifetime indicate a large degree of uncertainty. Here we use a detailed atmospheric model to calculate a current best estimate of the SF6lifetime. Read more
Chemical oxidative potential of secondary organic aerosol (SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds Atmospheric Chemistry and Physics DOI 10.5194/acp-17-839-2017 19 January 2017 Secondary organic aerosols (SOA) comprise a significant fraction of particulate matter (PM) and may have health implications. The water-soluble oxidative potentials of various SOA systems were determined using dithiothreitol consumption. Results from this study demonstrate that precursor identity was more influential than reaction condition in determining SOA oxidative potential and highlight a need to consider SOA contributions from anthropogenic hydrocarbons to PM-induced health effects. SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds">Read more
Radical chemistry at a rural site (Wangdu) in the North China Plain: observation and model calculations of OH, HO2 and RO2 radicals Atmospheric Chemistry and Physics DOI 10.5194/acp-17-663-2017 13 January 2017 In this study, we performed accurate OH measurements as well as selective HO2 and RO2 measurements at a rural site in North China Plain with state-of-the-art instruments newly developed. We confirmed the previous discovery on the enhancement of the OH in low NOx with which little O3 production was associated, and we found a missing RO2 source in high NOx which promoted higher O3 production. Our results are of vital importance for ozone abatement strategies currently under discussion for China. Read more
A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry Atmospheric Chemistry and Physics DOI 10.5194/acp-17-1-2017 2 January 2017 This paper summarizes two field measurements of particles and gases made in coastal Antarctica and represents the first real-time composition measurements of particles in this understudied area of the world. Using the combined data from both field measurements, we find that there is a constant background of particles in coastal Antarctica and that they are mostly sulfate. Seasonal transitions from winter to spring add additional particles, and that from spring to summer adds additional sulfate. Read more
Model sensitivity studies of the decrease in atmospheric carbon tetrachloride Atmospheric Chemistry and Physics DOI 10.5194/acp-16-15741-2016 20 December 2016 Carbon tetrachloride (CCl4) is a compound which, when released into the atmosphere, can cause depletion of the stratospheric ozone layer. Its emissions are controlled under the Montreal Protocol, and its atmospheric abundance is slowly decreasing. However, this decrease is not as fast as expected based on estimates of its emissions and its atmospheric lifetime. We have used an atmospheric model to look at the uncertainties in the CCl4lifetime and to examine the impact on its atmospheric decay. Read more
The acid-catalyzed hydrolysis of an α-pinene-derived organic nitrate: kinetics, products, reaction mechanisms, and atmospheric impact Atmospheric Chemistry and Physics DOI 10.5194/acp-16-15425-2016 13 December 2016 This study provides new insight into the hydrolysis reaction mechanism, which was elucidated for atmospherically relevant organic nitrates using kinetic measurements, product identification, and theoretical calculations. The results help broaden our knowledge of the organic chemistry that impacts the fate of NOx, ozone production, aerosol phase processing, and aerosol composition. Read more
Significant concentrations of nitryl chloride sustained in the morning: investigations of the causes and impacts on ozone production in a polluted region of northern China Atmospheric Chemistry and Physics DOI 10.5194/acp-16-14959-2016 5 December 2016 This work addresses the unclear global significance of chlorine activation processes in the troposphere. The first high-quality measurement data set of ClNO2in northern China revealed strong ClNO2 production in the residual layers, and demonstrated its significant effects on radical budget and ozone production. Our findings imply the widespread effects of ClNO2 over the polluted regions of northern China, which may increase photochemical and haze pollution. Read more