Hydrogen peroxide (HOOH) is an important oxidant that forms atmospheric sulfate. We demonstrate that the illumination of brown carbon can rapidly form HOOH within particles, even under the low-sunlight conditions of Fairbanks, Alaska, during winter. This in-particle formation of HOOH is fast enough that it forms sulfate at significant rates. In contrast, the formation of HOOH in the gas phase during the campaign is expected to be negligible because of high NO_x levels.

Exposure to high levels of ozone can be harmful to human health. This study shows consistent and robust evidence of decreasing ozone extremes across much of the United States over the period from 1990 to 2023, previously attributed to ozone precursor emission controls. Nevertheless, we also show that the increasing heat wave frequencies are likely to contribute to additional ozone exceedances, slowing the progress of decreasing the frequency of ozone exceedances.

Methane, the second most important anthropogenic greenhouse gas, is chemically decomposed in the atmosphere. The chemical sink of atmospheric methane is not constant but depends on the temperature and on the abundance of its reaction partners. In this study, we use a global chemistry–climate model to assess the feedback of atmospheric methane induced by changes in the chemical sink in a warming climate and its implications for the chemical composition and the surface air temperature change.

We developed an efficient GHG (greenhouse gas) flux inversion framework using a machine-learning emulator (FootNet) as a surrogate for an atmospheric transport model, resulting in a 650 × speedup. Paradoxically, the flux inversion using the ML (machine-learning) model outperforms the full-physics model in our case study. We attribute this to the ML model mitigating transport errors in the GHG flux inversion.

Dust-soluble iron deposition from East Asia plays an important role in the marine ecology of the Northwest Pacific. Using the developed model, our findings highlight a dual trend: a decrease in the overall deposition of soluble iron from dust but an increase in the solubility of the iron itself due to the enhanced atmospheric processing. The study underscores the critical roles of both dust emission and atmospheric processing in soluble iron deposition and marine ecology.

Observations from Atmospheric Chemistry Experiment–Fourier Transform Spectrometer (ACE-FTS) are used to examine global stratospheric water vapour trends for 2004–2021. The satellite measurements are used to quantify trend contributions arising from changes in tropical tropopause temperatures, general circulation patterns, and methane concentrations. While most of the observed trends can be explained by these changes, there remains an unaccounted-for and increasing source of water vapour in the lower mid-stratosphere at mid-latitudes, which is discussed.

This work provides the first fundamental laboratory data to evaluate SOA (secondary organic aerosol) production from styrene and NO₃ chemistry. Additionally, the formation mechanisms of aromatic organic nitrates (ONs) are reported, highlighting that previously identified nitroaromatics in ambient field campaigns can be aromatic ONs. Finally, the hydrolysis lifetimes observed for ONs generated from styrene and NO₃ oxidation can serve as experimentally constrained parameters for modeling hydrolysis of aromatic ONs in general.

This study explores how urban green spaces (UGSs) in Guangzhou influence ozone levels. By using advanced models, we found that natural emissions from these areas can significantly affect air quality. Our results suggest that the design and planning of UGSs should not only consider aesthetics and social factors but also their environmental impacts on air quality.

This study explores how aerosols affect clouds transitioning from stratocumulus to cumulus along trade winds under varying atmospheric conditions. We found that aerosols typically reduce precipitation and raise cloud height, but their impact changes when subsidence changes by aerosol enhancement are considered. Our findings indicate that the cooling effect of aerosols might be overestimated if these atmospheric changes are not accounted for.

A simple diagram to depict cloud droplets' formation via the activation of cloud condensation nuclei (CCN) as well as their subsequent growth and evaporation is presented.

Tropospheric O₃ molecules are labeled with the identity of their precursor source to simulate contributions from various emission sources to the global tropospheric O₃ burden (TOB) and its trends. With an equatorward shift, anthropogenic NO_x emissions become significantly more efficient at producing O₃ and play a major role in driving TOB trends, mainly due to larger convection at the tropics effectively lifting O₃ and its precursors to the free troposphere, where O₃ lifetime is longer.

Rain formation in warm clouds begins when small droplets collide, but this process can be slow without larger droplets. We used simulations to explore the role of bigger droplets, known as precipitation embryos, in triggering rain. We found that they speed up rain only when their size and number exceed a critical threshold. This threshold becomes larger when collisions are naturally efficient, such as in clouds with broad droplet size distributions or strong turbulence. 

Particle sources in polar climates are unclear, affecting climate representation in models. This study introduces an evaluated method for tracking particles with backward modeling. Tests on simulated particles allowed us to show that traditional detection methods often misidentify sources. An improved method that accurately traces the origins of aerosol particles in the Arctic is presented. The study recommends using this enhanced method for better source identification of atmospheric species.

This study presents long-term measurements and comprehensive analysis of carbonaceous aerosols in fine particles in Shanghai. We further estimated primary and secondary carbon levels, examining their temporal variations on interannual, monthly, seasonal, and diurnal scales. Through rigorous statistical analysis and correlation studies with meteorological parameters and pollutant concentrations, the origins, formation mechanisms, and spatial distribution patterns of secondary organic carbon were elucidated.

A measurement campaign in 2019 found that methane emissions from oil and gas in Romania were significantly higher than reported. In 2021, our follow-up campaign using airborne remote sensing showed a marked decreases in emissions by 20 %–60 % due to improved infrastructure. The study highlights the importance of measurement-based emission monitoring and illustrates the value of a multi-scale assessment integrating ground-based observations with large-scale airborne remote sensing campaigns.