We evaluate the environmental conditions that control how clouds grow from fair weather cumulus into severe thunderstorms during the Amazonian wet season. Days with rain clouds begin with more moisture in the air and have strong convergence in the afternoon, while precipitation intensity increases with large-scale vertical velocity, moisture, and low-level wind. These results contribute to understanding how clouds form over the rainforest.

The increasing concentration of O₃ precursors and unfavorable meteorological conditions are key factors in the formation of O₃ pollution in Zhengzhou. Vehicular exhausts (28 %), solvent usage (27 %), and industrial production (22 %) are identified as the main sources of NMVOCs. Moreover, O₃ formation in Zhengzhou is found to be in an anthropogenic volatile organic compound (AVOC)-limited regime. Thus, to reduce O₃ formation, a minimum AVOCs / NOx reduction ratio ≥ 3 : 1 is recommended.

The nitrous acid (HONO) budget was validated during a COVID-19 lockdown event. The main conclusions are (1) HONO concentrations showed a significant decrease from 0.97 to 0.53 ppb during lockdown; (2) vehicle emissions accounted for 53 % of nighttime sources, with the heterogeneous conversion of NO₂ on ground surfaces more important than aerosol; and (3) the dominant daytime source shifted from the homogenous reaction between NO and OH (51 %) to nitrate photolysis (53 %) during lockdown.

Large uncertainties remain in understanding secondary organic aerosol (SOA) formation and speciation from naphthalene oxidation. This study details the development of the first near-explicit chemical scheme for naphthalene oxidation by OH, which includes kinetic and mechanistic data, and is able to reproduce most of the experimentally identified products in both gas and particle phases.

Tropospheric ozone is a major air pollutant, a greenhouse gas, and a major indicator of model skill. Global atmospheric chemistry models show large differences in simulations of tropospheric ozone, but isolating sources of differences is complicated by different model environments. By implementing the GEOS-Chem model side by side to CAM-chem within a common Earth system model, we identify and evaluate specific differences between the two models and their impacts on key chemical species.

We found that the formation of the extreme trans-Atlantic African dust event in June 2015 was associated with a brief surge in dust emissions over western North Africa and extreme circulation patterns, including intensified easterly jets, which facilitated the westward transport of dust. The dust plume modified radiative flux along its transport pathway but had minor impacts on air quality in the US due to the record-high Caribbean low-level jet advecting part of the plume to the Pacific.

Aerosols can modify the liquid water path (LWP) of stratocumulus and, thus, their radiative effect. We compare storm-resolving model and satellite data that disagree on the sign of LWP adjustments and diagnose this discrepancy with causal inference. We find that strong precipitation, the absence of wet scavenging, and cloud deepening under a weak inversion contribute to positive LWP adjustments to aerosols in the model, despite weak negative effects from cloud-top entrainment enhancement. 

We explore a new method of using the wealth of information obtained from satellite observations of Aura OMI NO₂, HCHO, and MERRA-2 reanalysis in NASA’s GEOS model equipped with an efficient tropospheric OH (TOH) estimator to enhance the representation of TOH spatial distribution and its long-term trends. This new framework helps us pinpoint regional inaccuracies in TOH and differentiate between established prior knowledge and newly acquired information from satellites on TOH trends.

The turbulence in the planetary boundary layer (PBL) over the Tibetan Plateau (TP) remains unclear. Here we elucidate the vertical profile of and temporal variation in the turbulence dissipation rate in the PBL over the TP based on a radar wind profiler (RWP) network. To the best of our knowledge, this is the first time that the turbulence profile over the whole TP has been revealed. Furthermore, the possible mechanisms of clouds acting on the PBL turbulence structure are investigated.

This study investigated the distribution and sources of non-methane hydrocarbons (NMHCs) in the lower atmosphere over the marginal seas of China. NMHCs, a subset of volatile organic compounds (VOCs), play a crucial role in atmospheric chemistry. Derived from systematic atmospheric sampling in coastal cities and marginal sea regions, this study offers valuable insights into the interaction between land and sea in shaping offshore atmospheric NMHCs.

Environmental persistent free radicals (EPFRs) and reactive oxygen species (ROSs) play an active role in the atmosphere. Despite control measures having effectively reduced their emissions, reductions were less than in PM_2.5. Emission control measures performed well in achieving Parade Blue, but reducing the impact of the atmosphere on human health remains challenging. Thus, there is a need to reassess emission control measures to better address the challenges posed by EPFRs and ROSs.

The Amazon wet-season atmosphere was studied at the Amazon Tall Tower Observatory site, revealing vertical variations (between 60 and 325 m) in natural aerosols. Daytime mixing contrasted with nighttime stratification, with distinct rain-induced changes in aerosol populations. Notably, optical property recovery at higher levels was faster, while near-canopy aerosols showed higher scattering efficiency. These findings enhance our understanding of aerosol impacts on climate dynamics.

Using synthetic dropsondes, we assess how discrete spatial sampling and temporal evolution during flight affect the accuracy of real sonde-based moisture transport divergence in Arctic atmospheric rivers (ARs). Non-instantaneous sampling during temporal AR evolution deteriorates the divergence values more than spatial undersampling. Moisture advection is the dominating factor but most sensitive to the sampling method. We suggest a minimum of seven sondes to resolve the AR divergence components.

We investigated the causes of the decadal trends of solar radiation measured at 34 stations in Brazil in the first 2 decades of the 21st century. We observed strong negative trends in north and northeast Brazil associated with changes in both atmospheric absorption (anthropogenic) and cloud cover (natural). In other parts of the country no strong trends were observed as a result of competing effects. This provides a better understanding of the energy balance in the region.