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Decadal changes in global surface NOx emissions from multi-constituent satellite data assimilation

Global surface emissions of nitrogen oxides (NO_x) over a 10-year period (2005–2014) are estimated from assimilation of multiple satellite datasets. We present detailed distributions of the estimated NO_xemission 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.

Determination of the atmospheric lifetime and global warming potential of sulfur hexafluoride using a three-dimensional model

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.

Chemical oxidative potential of secondary organic aerosol (SOA) generated from the photooxidation of biogenic and anthropogenic volatile organic compounds

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

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 NO_x with which little O₃ production was associated, and we found a missing RO₂ source in high NO_x which promoted higher O₃ production. Our results are of vital importance for ozone abatement strategies currently under discussion for China.

A missing source of aerosols in Antarctica – beyond long-range transport, phytoplankton, and photochemistry

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.

Model sensitivity studies of the decrease in atmospheric carbon tetrachloride

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.

The acid-catalyzed hydrolysis of an α-pinene-derived organic nitrate: kinetics, products, reaction mechanisms, and atmospheric impact

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 NO_x, ozone production, aerosol phase processing, and aerosol composition.

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

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.

Quantifying the loss of processed natural gas within California’s South Coast Air Basin using long-term measurements of ethane and methane

This paper investigates the cause of the known underestimate of bottom-up inventories of methane in California’s South Coast Air Basin (SoCAB). We use total column measurements of methane, ethane, carbon monoxide, and other trace gases beginning in the late 1980s to calculate emissions and attribute sources of excess methane to the atmosphere. We conclude that more than half of the excess methane to the SoCAB atmosphere is attributable to processed natural gas.

The BErkeley Atmospheric CO2 Observation Network: initial evaluation

We describe the design of and first results from the BErkeley Atmospheric CO₂ Observation Network, a distributed instrument of 28 CO₂ sensors stationed across and around the city of Oakland, California at ~ 2 km intervals. We evaluate the network via 4 performance parameters (cost, reliability, precision, systematic uncertainty) and find this high density technique to be sufficiently cost-effective and rigorous to inform understanding of small-scale urban emissions relevant to climate regulation.

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