Multilayer clouds are common in the Arctic but remain underrepresented. We use an atmospheric model to simulate multilayer cloud cases from the Arctic expedition MOSAiC 2019/2020. We find that it is complex to accurately model these cloud layers due to the lack of correct temperature profiles. The model also struggles to capture the observed cloud phase and the relative concentration of cloud droplets and cloud ice. We constrain our model to measured aerosols to mitigate this issue.

The A-LIFE aircraft field experiment was carried out in the eastern Mediterranean in 2017. Using A-LIFE data, we studied the change in mineral dust optical properties due to mixing with anthropogenic aerosols. We found that increasing pollution affects dust optical properties, which has implications for identifying dust events and understanding their climate effects. We also show that optical properties of Saharan and Arabian dust are similar when comparing cases with equal pollution content.

We analyzed ground-level ozone variations and exposure hotspots across China (2000–2020) at multiple scales using daily 1 km ozone data derived from satellite-sourced land-surface temperature data via a machine-learning hindcasting model. The dataset was validated using cross-validation and external measurements. A non-monotonic trend with regional and seasonal variations emerged, with turning points around 2008 and 2015. Ozone levels >100 μg m‾³ shifted from June to May, while levels >160 μg m‾³ expanded in the North China Plain.

We analyzed in-cloud characteristics using in situ measurements from 42 research flights across two field campaigns into non-orographic, non-lake-effect winter storms. Much of the storm volume contains weak vertical motions (a few centimeters per second), and most updrafts ≥ 0.5 m s^-1 are small (< 1 km). Within 2 km of cloud radar echo top, stronger vertical motions and conditions for ice particle growth are more common. Overturning air motions near cloud top appear important for the production of snow particles.

This study aims to investigate how cloud seeding affects snowfall in Australia's Snowy Mountains. By running simulations with different setups, we found that seeding impact varies greatly with weather conditions. Seeding increased snow in stable weather but sometimes reduced it in stormy weather. This helps us to better understand when seeding works best to boost water supplies.

This study utilized the IPDA (integrated path differential absorption) lidar on board the DQ-1 satellite to monitor emissions from localized strong point sources and, for the first time, observed the diurnal variation in CO₂ emissions from a high-latitude power plant. Overall, power plant CO₂ emissions were largely consistent with local electricity consumption patterns, with most plants emitting less at night than during the day and with higher emissions in winter compared to spring and autumn.

Our research explores how SST (sea surface temperature) changes in non-polar regions impact the polar energy budget. Through idealized SST experiments, we found that warming in tropical and mid-latitude oceans raises polar temperatures through enhanced atmospheric energy transport, leading to surface warming and top-of-atmosphere cooling in polar areas. This study highlights the distinct impacts of tropical Pacific and Indian Ocean SST changes on Arctic and Antarctic climates.

This study estimated regional and sectoral emission contributions to the unprecedented surge of atmospheric methane for 2020–2022. The methane is the second most important greenhouse gas, and its emissions reduction is urgently required to mitigate global warming. Numerical modeling-based estimates with three different sets of atmospheric observations consistently suggested large contributions of biogenic emissions from South Asia and Southeast Asia to the surge of atmospheric methane.

Our study retrieved dust aerosol microphysical properties from lidar measurements using different scattering models. Numeric simulations and real data applications revealed the importance of considering depolarization measurements and the superiority of the irregular–hexahedral model in the retrieval of dust aerosols from lidar measurements.

This study investigates the variability and driving forces of transboundary CO transport flux over the Tibetan Plateau from May 2018 to April 2024. During this period, external CO influx increased by 2.86 Tg yr^-1, while internal efflux slightly declined by 1.70 Tg yr^-1. The rising influx in recent years is likely linked to the rapid increase in CO concentrations from South Asia.

Ice supersaturation is an immaterial feature that does not generally move with the wind that carries contrails and cirrus clouds. Here we analyse the different motions and show that ice supersaturated regions (ISSRs) on average move slower than the wind, the direction of movement is usually quite similar, and the distributions of both velocities follow Weibull distributions. The almost identical direction of the movements is beneficial for contrail lifetimes.

Strongly precipitating mesoscale convective systems produce a large amount of diabatic heating of the atmosphere, influencing atmospheric circulation. Their complete 3D description, attained by machine learning techniques in combination with satellite observations, has enabled a detailed study of the relationship between latent and radiative heating in these cloud systems. Convective organization increases both the average and the vertical gradient of radiative effects of the mesoscale convective systems.

We studied how air moves from the lower atmosphere to the stratosphere over the tropical western Pacific. Using observations and air tracking, we found that, in winter, air ascends and cold temperatures freeze water out, drying it before it enters the stratosphere. In summer, air tends to sink after cloud formation. This process affects water vapor amounts in the stratosphere, influencing the greenhouse effect and climate.

We investigated the sources and impacts of nitrogen oxides and organic compounds over a remote tropical island. Simulations of the high-resolution Weather Research and Forecasting model coupled with chemistry (WRF-Chem) were evaluated using in situ Fourier transform infrared spectroscopy (FTIR) and satellite measurements. This work highlights gaps in current models, like missing sources of key organic compounds and inaccuracies in emission inventories, emphasizing the importance of improving chemical and dynamical processes in atmospheric modelling for budget estimates in tropical regions.

Analyzing 12-year Zhengzhou data revealed post-2019 crustal material rebound caused by soil dust resuspension, elevating particle pH. Similar coarse particle increases are observed across cities of the North China Plain. Long-term particle acidity evolution in this region requires an integrated assessment of interactions among acidic precursors, ammonia, and crustal components.

This study examines how ship emissions affect clouds over a shipping corridor in the southeastern Atlantic. Using satellite data from 2004 to 2023, we find that ship emissions increase the number of cloud droplets while reducing their size and slightly decrease cloud water content. Effects on seasonal and daily patterns vary based on regional factors. The impact of emissions weakened after stricter regulations were implemented in 2020.

The daily concentrations of Polycyclic aromatic hydrocarbons (PAHs), oxygenated PAHs (OPAHs), and nitrated phenols (NPs) in PM_2.5 were all increased during the heating season. Biomass burning was identified to be the primary source of these aromatic compounds, particularly for PAHs. Phenol and nitrobenzene are two main primary precursors for 4NP, with phenol showing lower reaction barriers. P-Cresol was identified as the primary precursor for the formation of 4-methyl-5-nitrocatechol.

This study investigates H₂O₂ chemistry in rural North China. The observed H₂O₂ showed distinct diurnal variations influenced by photochemical reactions. A box model revealed that H₂O₂ is primarily produced by HO₂ recombination and removed mainly via particle uptake. Reductions in NO_x, PM_2.5, and alkanes raised H₂O₂ levels, while cutting alkenes, aromatics, CO, and HONO lowered them. A dual strategy focusing on VOC and NO_x control is essential to reduce both H₂O₂ and ozone pollution.

A structural-based parameterization for the photolysis rates of oxygenated volatile organic compounds (OVOCs) was integrated into an updated chemical mechanism. This method links photolysis rates to species' structure, bypassing limitations of insufficient quantum yield data. Box model results show that non-HCHO OVOCs, particularly multifunctional carbonyl compounds, significantly contribute to radical production, with alkene and aromatic oxidation products playing key roles.

Intermediate-volatility/semi-volatile organic compounds in gas and particle phases from ship exhausts are enhanced due to the switch of fuels from low sulfur to ultra-low sulfur. The findings indicate that optimization is necessary for the forthcoming global implementation of an ultra-low-sulfur oil policy. Besides, we find that organic diagnostic markers of hopanes in conjunction with the ratio of octadecanoic to tetradecanoic could be considered potential tracers for heavy fuel oil exhausts.

This study established an ammonia emission inventory for South Asia via an assimilation-based inversion system. The posterior emissions, calculated by integrating the anthropogenic inventory and satellite observations, showed significant improvement over the prior. Validation against various measurements supports our results. The study offers a deep understanding of ammonia emissions for policymakers and researchers aiming to develop air quality management and mitigation strategies for South Asia.

The current climate and environmental crises impose the need to take actions in cities to curb ozone as a pollutant and a climate forcer. This endeavor is challenging in understudied regions. In this work we analyze how reducing levels of precursor chemicals would affect ozone formation in Quito, Ecuador, and Santiago, Chile.  

We assess the drivers behind changes in peak-season surface ozone concentrations and risks to human health between 1850 and 2014. Substantial increases in surface ozone have occurred over this period, resulting in an increased risk to human health, driven mainly by increases in anthropogenic NO_x emissions and global CH₄ concentrations. Fixing anthropogenic NO_x emissions at 1850 values in the near-present-day period can eliminate the risk to human health associated with exposure to surface ozone.

We study the impact of the 2019–2020 Australian bushfires on stratospheric chemistry and polar stratospheric cloud (PSC) dynamics. Our results show that the stratospheric intrusion of bushfire aerosols significantly increases nitric acid in the lower stratosphere, thereby increasing the PSC volume during the Austral winter. Notably, rapid ice PSC nucleation on nitric acid trihydrate particles leads to unusually high ice PSC volumes, highlighting the response of PSCs to an enhanced stratospheric aerosol scenario.

Tropospheric ozone is an important greenhouse gas and is an air pollutant. The time variability of tropospheric ozone is mainly driven by anthropogenic emissions. In this paper, we study the distribution and time variability of ozone from harmonized ground-based observations from five different measurement techniques. Our findings provide clear standard references for atmospheric models and evolving tropospheric ozone satellite data for the 2000–2022 period.