Brewer spectroradiometers are widely used instruments that have been monitoring global solar ultraviolet (UV) irradiance since the 1990s, playing a key role in solar UV research. The uncertainties of these measurements are rarely evaluated even though they are essential to determine the quality of these measurements. In this work, the uncertainty of 10 Brewers is estimated using the Monte Carlo method, showing that Brewers’ relative uncertainty is less than 5 % for wavelengths above 310 nm.

Contrail cirrus is the largest, yet the most uncertain, aviation climate impact term. A newly implemented contrail cirrus scheme in a double-moment cloud microphysics scheme in climate model realistically reproduces the contrail evolution and provides regional forcing estimates within the range reported by other models. The work highlights the importance of initial contrail characteristics and the need for detailed cloud particle representations in climate model contrail simulations.

We compared different ways to define the upper barrier of the troposphere in the extra-tropics, the “tropopause”. By analysing ozone distributions sorted by different definitions, we found that the traditional temperature-based tropopause works less well than dynamic or tracer-based definitions. We saw a sharper transition of ozone across the tropopause using a higher value of potential vorticity than often used and recommend this value for future studies of exchange processes in this region.

The Russia-Ukraine war caused significant NOx emission reductions in Ukraine, exceeding COVID-19 impacts. Using TROPOMI data, we found a 15% drop in 2022 and 8% in 2023, with Eastern Ukraine (frontline) seeing declines of 29% and 17%. Industry emissions fell most (34% in 2022), while war-related NOx partially offset reductions (8-10%). Emissions closely tracked military actions, revealing conflict’s disruptive effects on socio-economic activity and air pollution.

This study uses machine learning to separate marine primary organic aerosol (POA) and secondary organic aerosol (SOA) from 1 decade of high-resolution data. POA averages 51 % of marine organic aerosols annually, peaking at 63 % in summer. A support vector regression model, validated via fuzzy clustering and Monte Carlo simulations, identifies seasonal patterns of POA linked to biological activity. We found diverse impacts of marine POA and SOA on the aerosol hygroscopicity and mixing state.

GAW-QC (Global Atmosphere Watch-Quality Control) is an interactive dashboard for the quality control of in-situ atmospheric composition measurements made at stations taking part in the Global Atmosphere Watch network. Even though it is mainly targeted at station operators who want to analyze recent, not yet published measurements, it allows anybody to verify the quality of already published measurements using various anomaly detection algorithms as well as visual comparisons.

Iodic acid (IA) particles are frequently observed in the upper troposphere and lower stratosphere (UTLS), yet their formation mechanism remains unclear. Nitric acid (NA) and ammonia (NH₃) are key nucleation precursors in the UTLS. This study investigates the IA–NA–NH₃ system using a theoretical approach. Our proposed nucleation mechanism highlights the crucial role of NA in IA nucleation, providing molecular-level evidence for the missing sources of IA particles in the UTLS.

Our study combines two data assimilation techniques to refine CH₄ emission estimates from natural wetlands in Norther Europe, combining parameter estimation of a vegetation model using eddy-covariance CH₄ flux measurements, and inverse modelling using atmospheric CH₄ measurements. We find a good complementarity between the two approaches, with the combined product leading to the overall best fit to observations, and arguably most realistic wetland CH₄ emission estimate.

We present a study of simultaneously measured fluxes of carbon dioxide (CO₂) and co-emitted species in the city of Zurich. Flux measurements of CO₂ alone cannot be attributed to specific emission sectors, such as road transport or residential heating. We present a model which uses the measured ratios of CO₂ to carbon monoxide (CO) and nitrogen oxides (NO_x) as well as sector-specific reference ratios, to attribute measured fluxes to their emission sectors.