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Mineralogy and physicochemical features of Saharan dust wet deposited in the Iberian Peninsula during an extreme red rain event

Saharan dust wet deposited in Granada (Spain) on 21–23 February 2017 during the most extreme red rain event of the last decades led to the deposition of ~ 140 000 T of dust just in the city of Granada, dwarfing any other standard Saharan dust events taking place in the area. The multianalytical study of Saharan dust disclosed potential source areas and the mineralogy and composition of the size fractions of desert dust as well as its potential biogeochemical, radiative, and health effects.

The diurnal cycle of cloud profiles over land and ocean between 51°S and 51°N, seen by the CATS spaceborne lidar from the International Space Station

From 3 years of observations from the CATS lidar on the International Space Station we document the daily cycle of the vertical distribution of clouds. This is the first time this is documented over several continents and oceans using finely resolved measurements on a near-global scale from a single instrument. We show that other instruments observing clouds from space, like CALIPSO, document extremes of the daily cycle over ocean and closer to the average over land.

CATS spaceborne lidar from the International Space Station">Read more

Transboundary ozone pollution across East Asia: daily evolution and photochemical production analysed by IASI + GOME2 multispectral satellite observations and models

This paper tackles a major issue for air quality over East Asia: ozone pollution produced over a major source, like the North China Plain, and the contribution of ozone produced while being transported across the continent and the surrounding seas. The main originality of the paper lays in the fact that this photochemical production of ozone is observationally quantified with new multispectral satellite observations offering unique skills to observe the ozone pollution plumes near the surface.

IASI + GOME2 multispectral satellite observations and models">Read more

High- and low-temperature pyrolysis profiles describe volatile organic compound emissions from western US wildfire fuels

We found that on average 85 % of the VOC emissions from biomass burning across various fuels representative of the western US (including various coniferous and chaparral fuels) can be explained using only two emission profiles: (i) a high-temperature pyrolysis profile and (ii) a low-temperature pyrolysis profile. The high-temperature profile is quantitatively similar between different fuel types (r² > 0.84), and likewise for the low-temperature profile.

Estimates of ozone return dates from Chemistry-Climate Model Initiative simulations

We analyse simulations from the Chemistry-Climate Model Initiative (CCMI) to estimate the return dates of the stratospheric ozone layer from depletion by anthropogenic chlorine and bromine. The simulations from 20 models project that global column ozone will return to 1980 values in 2047 (uncertainty range 2042–2052). Return dates in other regions vary depending on factors related to climate change and importance of chlorine and bromine. Column ozone in the tropics may continue to decline.

Surface impacts of the Quasi Biennial Oscillation

A major phenomenon in the stratosphere is the Quasi Biennial Oscillation (QBO). Although a feature of the equatorial stratosphere, its influence extends to surface weather at both equatorial and mid latitudes. Improved knowledge of mechanisms of influence should help to improve weather forecasts. In this paper, QBO impacts at the surface are characterized and dominant mechanisms explored. Three pathways are identified, referred to as the tropical, subtropical and polar routes.

On ozone trend detection: using coupled chemistry–climate simulations to investigate early signs of total column ozone recovery

2017 marks the 30th anniversary of the Montreal Protocol, which was implemented to protect the stratospheric ozone layer from the harmful effects of synthetic ozone depleting substances. Since the late 1990s atmospheric concentrations of these species have begun to decline, and as a result ozone concentrations are expected to increase. In this study we use an ensemble of chemistry–climate simulations to investigate recent ozone trends and search for early signs of ozone recovery.

Contrails and their impact on shortwave radiation and photovoltaic power production – a regional model study

A numerical model also used for operational weather forecast was applied to investigate the impact of contrails and contrail cirrus on the radiative fluxes at the earth’s surface. Accounting for contrails produced by aircraft enables the model to simulate high clouds that are otherwise missing. In a case study, we find that the effect of these extra clouds is to reduce the incoming shortwave radiation at the surface as well as the production of photovoltaic power by up to 10 %.

Global evaluation and calibration of a passive air sampler for gaseous mercury

A new passive air sampler for gaseous mercury was tested at 20 sites on four continents. These sites have in common that they use the state-of-the-art active air sampling technique for gaseous mercury on a continuous basis and therefore allow for an evaluation and calibration of the passive sampler. The sampler proved to work exceptionally well, with a precision and accuracy on par with the active instrument and better than what has previously been achieved with passive samplers.

Novel pathway of SO₂ oxidation in the atmosphere: reactions with monoterpene ozonolysis intermediates and secondary organic aerosol

Synergistic effects between SOA formation and SO₂ oxidation through Criegee chemistry and reactive uptake by organic peroxides were observed. The relative importance of these two pathways (Criegee vs. peroxide) varies with relative humidity. The latter SO₂ loss mechanism to organic peroxides in SOA has not previously been identified. Our results suggest a new pathway of atmospheric SO₂ oxidation, which may contribute to the missing mechanisms of high-sulfate production in the polluted areas.

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