Clouds are essential to keep Earth cooler by reflecting sunlight back to space. We show that an increase in aerosol concentration suppresses precipitation in clouds, causing them to accumulate water and expand in a polluted environment with stronger turbulence and radiative cooling. This process enhances their reflectance by 51 %. It is therefore prudent to account for cloud fraction changes in assessments of aerosol–cloud interactions to improve predictions of climate change.

The planetary boundary layer is critical to our climate system. This study uses a deep learning approach to estimate the planetary boundary layer height (PBLH) from conventional meteorological measurements. By training data from comprehensive field observations, our model examines the influence of various meteorological factors on PBLH and demonstrates effectiveness across different scenarios, offering a reliable tool for understanding boundary layer dynamics.

Aerosol particles from mainland can transport to oceans and deposit, providing soluble Fe and affecting phytoplankton growth. Thus, we studied the dissolution process of aerosol Fe and found that photochemistry played a key role in promoting Fe dissolution in clean conditions. RH-dependent reactions were more influential in slightly polluted conditions. These results highlight the distinct roles of two weather-related parameters (radiation and RH) in influencing geochemical cycles related to Fe.

The variations in anthropogenic aerosol concentrations and source contributions and their subsequent radiative impact in major emission regions during historical periods are quantified based on an aerosol-tagging system in E3SMv1. Due to the industrial development and implementation of economic policies, sources of anthropogenic aerosols show different variations, which has important implications for pollution prevention and control measures and decision-making for global collaboration.

Nitrated aromatic compounds (NACs) and oxygenated derivatives of polycyclic aromatic hydrocarbons (OPAHs) in PM_2.5 were examined from an urban area in Beijing during the autumn and winter. The OPAH and NAC concentrations were much higher during heating than before heating. They majorly originated from the combustion of biomass and automobile emissions, and the secondary generation was the major contributor throughout the whole sampling period.

We attempt to use a novel structural self-organising map and machine learning models to identify a weather system and quantify the importance of each meteorological factor in driving the unexpected PM_2.5 and O₃ changes under the specific weather system during the COVID-19 lockdown in China. The result highlights that temperature under the double-centre high-pressure system plays the most crucial role in abnormal events.

We examined the links between the El Niño–Southern Oscillation (ENSO) and tropospheric ozone (O₃) using model data. Our results show that ENSO impacts on tropospheric O₃ are mainly found over oceans, while the signature of ENSO over continents is largely unclear. These impacts in the midlatitude regions over the Southern Hemisphere may be more significant than previously known. The responses of O₃ to ENSO are weak in the middle troposphere and stronger in the upper and lower troposphere.

Persistent phenoxy radical (PPR), formed by phenol gas oxidation and its aqueous reaction, catalytically destroys O₃ and retards secondary organic aerosol (SOA) growth. Explicit gas mechanisms including the formation of PPR and low-volatility products from the oxidation of phenol or benzene are applied to the UNIPAR model to predict SOA mass via multiphase reactions of precursors. Aqueous reactions of reactive organics increase SOA mass but retard SOA growth via heterogeneously formed PPR.

pH is a key property of ambient aerosols, which affect many atmospheric processes. As aerosol pH is a non-conservative parameter, diverse averaging metrics and temporal resolutions may influence the pH values calculated by thermodynamic models. This technical note seeks to quantitatively evaluate the average pH using varied metrics and resolutions. The ultimate goal is to establish standardized reporting practices in future research endeavors.

We evaluate the long-term (2000–2020) variabilities of aerosol absorption optical depth, black carbon emissions, and associated health risks in China with an integrated framework that combines multiple observations and modeling techniques. We demonstrate the remarkable emission abatement resulting from the implementation of national pollution controls and show how human activities affected the emissions with a spatiotemporal heterogeneity, thus supporting differentiated policy-making by region.

Cloud types are determined using machine learning image classifiers applied to satellite imagery for 1 year in the North Atlantic. This survey of these cloud types shows that the climate impact of a cloud scene is, in part, a function of cloud type. Each type displays a different mix of thick and thin cloud cover, with the fraction of thin cloud cover having the strongest impact on the clouds' radiative effect. Future studies must account for differing properties and processes among cloud types.

This study examines the role of atmospheric aerosols in winter fog over the Indo-Gangetic Plains of India using WRF-Chem.  The increase in RH with aerosol–radiation feedback (ARF) is found to be important for fog formation as it promotes the growth of aerosols in the polluted environment. Aqueous-phase chemistry in the fog increases PM_2.5 concentration, further affecting ARF. ARF and aqueous-phase chemistry affect the fog intensity and the timing of fog formation by ~1–2 h.

We present novel findings on convective rainfall, summer rain in the late afternoon, by coupling water stable isotopes, micro rain radar, and satellite data. We found the tallest clouds in the afternoon and much smaller clouds at night, resulting in differences in day–night ratios in water stable isotopes. We sampled rain and meteorological variables every 5–10 min, allowing us to evaluate the development of convective rainfall, contributing to knowledge  of rainfall related to extreme events.

We demonstrate what can be learned about an Antarctic region's climate from basic atmospheric irradiance measurements made by broadband and filter radiometers, instruments suitable for deployment at very remote sites, assisted by meteorological reanalysis and satellite remote sensing. Analysis of shortwave and longwave irradiance reveals subtle contrasts between meteorological regimes favoring cloud ice versus liquid water, relevant to onset versus inhibition of surface melt over ice shelves.

This study presents concurrent online measurements of organic gas and particles (VOCs and OA) at a forested site in summer. Both VOCs and OA were largely contributed by oxygenated organic compounds. Semi-volatile oxygenated OA and organic nitrate formed from monoterpenes and sesquiterpenes contributed significantly to nighttime particle growth. The results help us to understand the causes of nighttime particle growth regularly observed in summer in central European rural forested environments.

NO₂ is a gas with implications for air pollution. A campaign conducted in Houston provided an opportunity to compare NO₂ from different instruments and a model. Aircraft and satellite observations agreed well with measurements on the ground; however, the latter estimated lower values. We find that model-simulated NO₂ was lower than observations, especially downtown, suggesting that NO₂ sources associated with the urban core of Houston, such as vehicle emissions, may be underestimated.

The current understanding and observational evidence do not provide any support for the possibility of an ozone hole occurring outside Antarctica today with respect to the present-day stratospheric halogen levels.

We provide evidence that light enhances the conversion of SO₂ to sulfates on non-photoactive mineral dust, where triplet states of SO₂ (³SO₂) can act as a pivotal trigger to generate sulfates. Photochemical sulfate formation depends on H₂O, O₂, and basicity of mineral dust. The SO₂ photochemistry on non-photoactive mineral dust contributes to sulfates, highlighting previously unknown pathways to better explain the missing sources of atmospheric sulfates.

We used a 20-bin WRF-Chem model to simulate NPF events in the NCP during a three-week observational period in the summer of 2019. The model was able to reproduce the observations during June 29–July 6, which was characterized by a high frequency of NPF occurrence.

In this study, we diagnose uncertainties in carbon monoxide and organic carbon emissions from four inventories for seven major wildfire-prone regions. Uncertainties in vegetation classification methods, fire detection products, and cloud obscuration effects lead to bias in these biomass burning (BB) emission inventories. By comparing simulations with measurements, we provide certain inventory recommendations. Our study has implications for reducing uncertainties in emissions in further studies.

Advection fog occurs when warm and moist air moves over a cold sea surface. In this situation, the temperature of the foggy air usually drops below the sea surface temperature (SST), particularly at night. High-resolution simulations show that the cooling effect of longwave radiation from the top of the fog layer permeates through the fog, resulting in a cooling of the surface air below SST. This study emphasizes the significance of monitoring air temperature to enhance sea fog forecasting.

We present simulations with a high-resolution numerical weather prediction model to study the growth of ice crystals in low clouds following glaciogenic seeding. We show that the simulated ice crystals grow slower than observed and do not consume as many cloud droplets as measured in the field. This may have implications for forecasting precipitation, as the ice phase is crucial for precipitation at middle and high latitudes.

Venezuela's Lake Maracaibo region is notoriously hard to observe from space and features intensive oil exploitation, although production has strongly decreased in recent years. We estimate methane emissions using 2018–2020 TROPOMI satellite observations with national and regional transport models. Despite the production decrease, we find relatively constant emissions from Lake Maracaibo between 2018 and 2020, indicating that there could be large emissions from abandoned infrastructure.

Online vertical gradient measurements of formic and isocyanic acids were made based on a 320 m tower in a megacity. Vertical variations and sources of the two acids were analyzed in this study. We find that formic and isocyanic acids exhibited positive vertical gradients and were mainly contributed by photochemical formations. The formation of formic and isocyanic acids was also significantly enhanced in urban regions aloft.

The knowledge of properties from dust emitted in high latitudes such as in Iceland is scarce. This study focuses on the particle size, mineralogy, cohesion, and iron mode of occurrence and reflectance spectra of dust-emitting sediments. Icelandic top sediments have lower cohesion state, coarser particle size, distinctive mineralogy, and 3-fold bulk Fe content, with a large presence of magnetite compared to Saharan crusts.

The retrieval of refractive indices of dust aerosols from laboratory optical measurements is commonly done assuming spherical particles. This paper aims to investigate the uncertainties in the shortwave refractive indices and corresponding optical properties by considering non-spherical and inhomogeneous models for dust samples. The study emphasizes the significance of using non-spherical models for simulating dust aerosols.

Wildfires in California (CA) have grown very large during the past 20 years. These fires emit sunlight-absorbing aerosols. Analyzing observational data, our study finds that aerosols emitted from large fires in northern CA spread throughout CA and Nevada and heat the atmosphere. This heating is consistent with larger-than-normal temperatures and dry conditions. Further study is needed to determine how much the aerosols heat the atmosphere and whether they are drying the atmosphere as well.