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Vertical profiles of light absorption and scattering associated with black carbon particle fractions in the springtime Arctic above 79∘ N

Black carbon is a factor in the warming of the Arctic atmosphere due to its ability to absorb light, but the uncertainty is high and few observations have been made in the high Arctic above 80° N. We combine airborne and ground-based observations in the springtime Arctic, at and above 80° N, with simulations from a global model to show that light absorption by black carbon may be much larger than modelled. However, the uncertainty remains high.

Comparing secondary organic aerosol (SOA) volatility distributions derived from isothermal SOA particle evaporation data and FIGAERO–CIMS measurements

We compared the volatility distributions of secondary organic aerosol (SOA) constituents estimated from isothermal evaporation experiments from either particle size change data, by process modelling and global optimization, or from mass spectrometer data with positive matrix factorization analysis. Our results show that, despite the two very different estimation methods, the volatility distributions are comparable if uncertainties are taken into account.

SOA) volatility distributions derived from isothermal SOA particle evaporation data and FIGAERO–CIMS measurements">Read more

Quantifying burning efficiency in megacities using the NO2/CO ratio fromthe Tropospheric Monitoring Instrument (TROPOMI)

Rapid urbanization has increased the consumption of fossil fuel, contributing the degradation of urban air quality. Burning efficiency is a major factor determining the impact of fuel burning on the environment. We quantify the burning efficiency of fossil fuel use over six megacities using satellite remote sensing data. City governance can use these results to understand air pollution scenarios and to formulate effective air pollution control strategies.

TROPOMI)">Read more

The value of remote marine aerosol measurements for constraining radiative forcing uncertainty

The amount of energy reflected back into space because of man-made particles is highly uncertain. Processes related to naturally occurring particles cause most of the uncertainty, but these processes are poorly constrained by present-day measurements. We show that measurements over the Southern Ocean, far from pollution sources, efficiently reduce climate model uncertainties. Our results pave the way to designing experiments and measurement campaigns that reduce this uncertainty even further.

A semi-empirical potential energy surface and line list for H216O extending into the near-ultraviolet

Water vapour has a complex spectrum and absorbs from the microwave to the near-UV where it dissociates. There is limited knowledge of the absorption features in the near-UV, and there is a large disagreement for the available models and experiments. We created a new ab initio model that is in good agreement with observation at 363 nm. At lower wavelengths, our calculations suggest that the latest experiments overestimate absorption. This has implications for trace gas retrievals in the near-UV.

Revisiting global satellite observations of stratospheric cirrus clouds

Cirrus clouds appearing in the upper troposphere and lower stratosphere have important impacts on the radiation budget and climate change. We revisited global stratospheric cirrus clouds with CALIPSO and for the first time with MIPAS satellite observations. Stratospheric cirrus clouds related to deep convection are frequently detected in the tropics. At middle latitudes, MIPAS detects more than twice as many stratospheric cirrus clouds due to higher detection sensitivity.

Inconsistencies between chemistry–climate models and observed lower stratospheric ozone trends since 1998

Recent lower stratospheric ozone decreases remain unexplained. We show that chemistry–climate models are not generally able to reproduce mid-latitude ozone and water vapour changes. Our analysis of observations provides evidence that climate change may be responsible for the ozone trends. While model projections suggest that extratropical ozone should recover by 2100, our study raises questions about their efficacy in simulating lower stratospheric changes in this region.

Effective radiative forcing and adjustments in CMIP6 models

The spread in effective radiative forcing for both CO ₂ and aerosols is narrower in the latest CMIP6 (Coupled Model Intercomparison Project) generation than in CMIP5. For the case of CO ₂ it is likely that model radiation parameterisations have improved. Tropospheric and stratospheric radiative adjustments to the forcing behave differently for different forcing agents, and there is still significant diversity in how clouds respond to forcings, particularly for total anthropogenic forcing.

Molecular understanding of new-particle formation from α-pinene between-50 and +25 ∘C

Highly oxygenated organic compounds (HOMs) have been identified as key vapors involved in atmospheric new-particle formation (NPF). The molecular distribution, HOM yield, and NPF from α-pinene oxidation experiments were measured at the CLOUD chamber over a wide tropospheric-temperature range. This study shows on a molecular scale that despite the sharp reduction in HOM yield at lower temperatures, the reduced volatility counteracts this effect and leads to an overall increase in the NPF rate.

Remote sensing of methane leakage from natural gas and petroleum systems revisited

The switch from the use of coal to natural gas or oil for energy generation potentially reduces the impact on global warming due to lower CO ₂ emissions with the same energy content. However, this climate benefit is offset by fugitive methane emissions during the production and distribution process. We quantify emission and leakage rates relative to production for several large production regions based on satellite observations to evaluate the climate footprint of the gas and oil industry.

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