In this paper, we describe the details of a new multi-model intercomparison experiment to assess the effects of Stratospheric Aerosol Intervention (SAI) on stratospheric chemistry and dynamics and, therefore, ozone. Second, we discuss the advantages and differences of the more constrained experiment compared to fully interactive model experiments. This way, we advance the process-level understanding of the drivers of SAI-induced atmospheric responses.

Convective clouds are a key component of the climate system. Using remote sensing observations during two field experiments in Houston, Texas, we identify four diurnal patterns of shallow convective clouds. We find areas more frequently experiencing shallow convective clouds, and we find areas where the vertical extent of shallow convective clouds is higher and where they are more likely to precipitate. This provides insight into the complicated environment that forms these clouds in Houston.

This study assesses the potential of the Ozone Monitoring Instrument (OMI) and the TROPOspheric Monitoring Instrument (TROPOMI) satellite observations to inform about the decrease in anthropogenic emissions of nitrogen oxides (NO_x) in 2019 compared with 2005 at regional to national scales in Europe. Both the OMI and TROPOMI inversions show decreases in European NO_x anthropogenic emission budgets in 2019 compared to 2005 but with different magnitudes.

The study investigates how aerosol–cloud interactions affect warm boundary layer stratiform clouds over the eastern North Atlantic. High-resolution weather model simulations reveal that non-rain clouds at the edge of cloud systems are prone to evaporation, leading to an aerosol drying effect and a transition of aerosols back to the accumulation mode for future activation. The study shows that this dynamic behavior is often not adequately represented in most previous prescribed-aerosol simulations.

The Ozone Monitoring Instrument (OMI) was used to understand the evolution of NO_x emissions from the Canadian oil sands. OMI NO₂ combined with winds and reported stack emissions found emissions from the heavy-hauler mine fleet have remained flat since 2005, whereas the total oil sands mined have more than doubled. This difference is a result of emissions standards that limit NO_x emissions becoming more stringent over this period, confirming the efficacy of the policy enacting these standards.

Shallow clouds in the trades are a major source of uncertainty in climate projections. These clouds organize into striking mesoscale patterns that are exactly what climate models lack. This study explores the origin of such patterns and investigates how variations in microscale properties control them. The importance of microscale effects is compared to that of large-scale forcing on the mesoscale organization of trade-cumulus fields.

Injecting sea salt aerosols into marine stratiform clouds can distribute the cloud water over more droplets in smaller sizes. This process is expected to make the clouds brighter, allowing them to reflect more sunlight back to space. However, it may also cause the clouds to lose water over time, reducing their ability to reflect sunlight. We use a computer model to show that the loss of cloud water occurs relatively quickly and does not completely offset the initial brightening.

To improve air quality, the Chinese government has implemented strict clean-air measures. We explored how black carbon (BC) responded to these measures and found that a reduction in liquid fuel use was the main factor driving a decrease in BC levels. Additionally, meteorological factors also played a significant role in the long-term trends of BC. These factors should be considered in future emission reduction policies to further enhance air quality improvements.

Lignin and Snomax are surface-active macromolecules that show a relationship between increasing concentrations, decreasing surface tension, and increasing ice-nucleating ability. However, this relationship did not hold for agricultural soil extracts collected in the UK and Canada. To explain this difference, we propose that as the complexity of the sample increases, the hydrophobic interfaces in the bulk compete with the air–water interface.

Traditional numerical schemes of aerosol chemistry and interactions (ACI) in atmospheric models are computationally costly and are often simplified or omitted, introducing uncertainties. We use an AI scheme to achieve fast, accurate, and stable end-to-end simulation for full ACI within an atmospheric model, replacing numerical schemes. This innovation is expected to enhance the accuracy and efficiency of ACI simulations in climate models that would otherwise neglect or simplify ACI processes.

This study uses dry CO₂ mole fractions from the Amazon Tall Tower Observatory together with airborne profiles to estimate net carbon exchange in tropical South America. We found that the biogeographic Amazon is a net carbon sink, while the Cerrado and Caatinga biomes are net carbon sources, resulting in an overall neutral balance. Finally, to further reduce the uncertainty in our estimates we call for an expansion of the monitoring capacity, especially in the Amazon–Andes foothills.

This paper details a novel method of measuring the volatility of pesticides using the Filter Inlet for Gases and AEROsols coupled with a chemical ionisation mass spectrometer (FIGAERO-CIMS) calibrated using a set of poly(ethylene) glycols. This is compared to literature values and common models. The results show that the method used primarily matches current literature values. Additionally, a pesticide’s volatility as an indicator of the likelihood of atmospheric transport occurring is explored.

In this study, we evaluate the present state of modelling lightning flashes over the Northern Hemisphere, using the classical CTH (cloud-top height) scheme and the ICEFLUX scheme with the CHIMERE model. Our study provides a comprehensive 3D comparison of model outputs to assess the robustness and applicability of these schemes. An improvement in O₃ distribution in the tropical free troposphere is observed due to inclusion of LNO_x (nitrogen oxide emissions from lightning) in the model. Inclusion of LNO_x also reduces the lifetime of trace gas CH₄.

In this work, the methane emissions from the rice crops of the Ebro Delta were estimated with the Radon Tracer Method, using back trajectories and radon and methane observations. Estimated fluxes show a strong seasonality with maximums in October, corresponding with the period of harvest and straw incorporation. The estimated annual methane emission was about 262.8 kg CH₄ ha^‑1. Results were compared with fluxes obtained with static chambers showing strong agreement between both methodologies.

This works analyzes the aerosol scattering phase function for transported Saharan dust to the city of Granada – located in southwestern Europe. We use the novel technique polar imaging nephelometry that helps to determine the phase functions using a CMOS camera. The capability of measuring with polarized light helps to infer new properties about the mixture of Saharan dust particles with those of anthropogenic origin.

The Hunga Tonga–Hunga Ha’apai volcano erupted on 15 January 2022, producing the largest stratospheric aerosol perturbation of the last 30 years. Stratospheric volcanic aerosols usually produce a transient climate cooling; these impacts depend on volcanic aerosol composition/size, due to size-dependent interactions with solar/terrestrial radiation. We demonstrate that the Hunga Tonga–Hunga Ha’apai stratospheric aerosols have a larger cooling potential per unit mass than the past climate-relevant El Chichón (1984) and Pinatubo (1991) eruptions.

Biomass burning has a considerable effect on the chemical composition of the atmosphere and climate, due to the emission of trace gases and aerosols. We examine the relationship between fire variability and the values of carbon monoxide and aerosol optical depth observed by satellites. The observed increase in wildfires has led to a corresponding rise in the mean and extreme values of carbon monoxide and aerosol optical depth during the summer and early autumn across the Northern Hemisphere.

We directly measured the dinitrogen pentoxide (N₂O₅) uptake coefficient using an aerosol flow tube, which critically impacts the NO_x fate and particulate nitrate formation in a typical highland city, Kunming, in China. We found that the performance of current γ (N₂O₅) parameterizations showed deviations with the varying aerosol liquid water content (ALWC). Such differences would lead to biased estimation of particulate nitrate production potential. We give suggestions for future research directions.

The spectral optical properties of combustion soot aerosols with varying black (BC) and brown carbon (BrC) content were studied in an atmospheric simulation chamber. Measurements of the mass spectral absorption cross section (MAC), supplemented by literature data, allowed us to establish a generalised exponential relationship between the spectral absorption and the elemental-to-total-carbon ratio (EC / TC) in soot. This relationship can provide a useful tool for modelling the properties of soot.

This study explores how uncertainties in the representation of microphysical processes affect the tropical condensate distribution in the global storm-resolving model ICON. The results point to the importance of the fall speed of hydrometeor particles and to a simple relationship: the faster a condensate falls, the less there is of it. Implications for the energy balance and precipitation properties are discussed.

We used atmospheric measurements and inverse modelling to estimate New Zealand's carbon dioxide (CO₂) emissions and removals from 2011 to 2020. Our study reveals that New Zealand's land absorbs more CO₂ than previously estimated, particularly in areas dominated by indigenous forests. Our results highlight gaps in current national CO₂ estimates and methods, suggesting a need for further research to improve emissions reports and refine approaches to track progress toward climate mitigation goals.

Our study reveals how water vapor, directed by seasonal winds, shapes precipitation isotopes in China's Dongting Lake basin. We traced water vapor paths, showing their impact on water supply and climate. This insight is key for predicting future water resources and climate patterns, offering a clearer understanding of our interconnected environmental systems.

Particulate methanesulfonic acid (MSA_p) is vital for the Arctic climate system. Numerical models struggle to reproduce the MSA_p seasonal cycle. We evaluate three numerical models and one reanalysis product’s ability to simulate MSA_p. We develop data-driven models for MSA_p at four Arctic stations. The data-driven models outperform the numerical models and reanalysis product and identified precursor source-, chemical-processing-, and removal-related features as being important for modeling MSA_p.

This study documents vertical profiles of liquid water content (LWC) in fogs from in situ measurements collected during the SOFOG3D field campaign in 2019–2020. The analysis of 140 vertical profiles reveals a reverse trend in LWC, maximum values at ground decreasing with height, during stable conditions in optically thin fogs, evolving towards quasi-adiabatic characteristics when fogs become thick. These results offer new perspectives for better constraining fog numerical simulations.

A summer campaign in a Mediterranean port examined pollution caused by ships. Two stations in the port measured pollution levels and captured over 350 ship plumes to study their chemical composition. Results showed that pollution levels, such as ultra-fine particles, were higher in the port than in the city and offer strong support to improve emission inventories. These findings may also serve as reference to assess the benefits of a sulfur Emission Control Area in the Mediterranean in 2025.