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Smoke of extreme Australian bushfires observed in the stratosphere over Punta Arenas, Chile, in January 2020: optical thickness, lidar ratios, and depolarization ratios at 355 and 532 nm

Unique lidar observations of a strong perturbation in stratospheric aerosol conditions in the Southern Hemisphere caused by the extreme Australian bushfires in 2019–2020 are presented. One of the main goals of this article is to provide the CALIPSO and Aeolus spaceborne lidar science teams with basic input parameters (lidar ratios, depolarization ratios) for a trustworthy documentation of this record-breaking event.

Identifying a regional aerosol baseline in the eastern North Atlantic using collocated measurements and a mathematical algorithm to mask high-submicron-number-concentration aerosol events

Continuous high-time-resolution ambient data can include periods when aerosol properties do not represent regional aerosol processes due to high-concentration local events. We develop a novel aerosol mask at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) facility in the eastern North Atlantic (ENA). We use two ground sites to validate the mask, include a comparison with aircraft overflights, and provide guidance to increase data quality at ENA and other locations.

Enhanced growth rate of atmospheric particles from sulfuric acid

Sulfuric acid is a major atmospheric vapour for aerosol formation. If new particles grow fast enough, they can act as cloud droplet seeds or affect air quality. In a controlled laboratory set-up, we demonstrate that van der Waals forces enhance growth from sulfuric acid. We disentangle the effects of ammonia, ions and particle hydration, presenting a complete picture of sulfuric acid growth from molecular clusters onwards. In a climate model, we show its influence on the global aerosol budget.

Modelling the potential impacts of the recent, unexpected increase in CFC-11 emissions on total column ozone recovery

The Montreal Protocol was agreed in 1987 to limit and then stop the production of man-made CFCs, which destroy stratospheric ozone. As a result, the atmospheric abundances of CFCs are now declining in the atmosphere. However, the atmospheric abundance of CFC-11 is not declining as expected under complete compliance with the Montreal Protocol. Using the UM-UKCA chemistry–climate model, we explore the impact of future unregulated production of CFC-11 on ozone recovery.

CFC-11 emissions on total column ozone recovery">Read more

Exploration of oxidative chemistry and secondary organic aerosol formation in the Amazon during the wet season:explicit modeling of the Manaus urban plume with GECKO-A

The GoAmazon 2014/5 field campaign took place near the city of Manaus, Brazil, isolated in the Amazon rainforest, to study the impacts of urban pollution on natural air masses. We simulated this campaign with an extremely detailed organic chemistry model to understand how the city would affect the growth and composition of natural aerosol particles. Discrepancies between the model and the measurements indicate that the chemistry of naturally emitted organic compounds is still poorly understood.

GECKO-A">Read more

Dynamic projection of anthropogenic emissions in China: methodology and 2015–2050 emission pathways under a range of socio-economic, climate policy, and pollution control scenarios

Future trends in air pollution and greenhouse gas emissions in China are of great concern to the community. Here we developed a sophisticated dynamic projection model to understand 2015–2050 emission pathways under a range of socio-economic, climate policy, and pollution control scenarios. By coupling strong low-carbon transitions and clean air policy, emissions of major air pollutants in China will be reduced by 58–87 % during 2015–2050. This work can support future co-governance policy design.

The acidity of atmospheric particles and clouds

Acid rain is recognized for its impacts on human health and ecosystems, and programs to mitigate these effects have had implications for atmospheric acidity. Historical measurements indicate that cloud and fog droplet acidity has changed in recent decades in response to controls on emissions from human activity, while the limited trend data for suspended particles indicate acidity may be relatively constant. This review synthesizes knowledge on the acidity of atmospheric particles and clouds.

Oxygen and sulfur mass-independent isotopic signatures in black crusts: thecomplementary negative Δ33S reservoir of sulfate aerosols?

Given their critical impact on radiative forcing, sulfate aerosols have been extensively studied using their isotope signatures (δ ³⁴ S, ∆ ³³ S, ∆ ³⁶ S, δ ¹⁸ O, and ∆ ¹⁷ O). A striking observation is that ∆ ³³ S > 0 ‰, implying a missing reservoir in the sulfur cycle. Here, we measured ∆ ³³ S < 0 ‰ in black crust sulfates (i.e., formed on carbonate walls) that must therefore result from distinct chemical pathway(s) compared to sulfate aerosols, and they may well represent this complementary reservoir.

Technical note: Preparation and purification of atmospherically relevant α-hydroxynitrate esters of monoterpenes

This report describes a simple, safe and effective method to prepare nitrate esters of terpenes (carene, limonene, perillic alcohol, beta-pinene and alpha-pinene) which are key oxidation products in the atmosphere. These compounds are implicated in the formation of secondary organic aerosols. A compilation of the relevant spectroscopic data has been presented. The availability of these compounds and their characterization data will enable further study of the structure–reactivity relationships.

Supercooled liquid water cloud observed, analysed, and modelled at the top ofthe planetary boundary layer above Dome C, Antarctica

Thin (~ 100 m) supercooled liquid water (SLW, water staying in liquid phase below 0 °C) clouds have been detected, analysed, and modelled over the Dome C (Concordia, Antarctica) station during the austral summer 2018–2019 using observations and meteorological analyses. The SLW clouds were observed at the top of the planetary boundary layer and the SLW content was always strongly underestimated by the model indicating an incorrect simulation of the surface energy budget of the Antarctic Plateau.

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