We use a numerical model to study interactions between humid light-absorbing aerosol plumes, clouds, and radiation over the southeast Atlantic. We find that the warming produced by the aerosols reduces cloud cover, especially in highly polluted situations. Aerosol impacts on drizzle play a minor role. However, aerosol effects on cloud reflectivity and moisture-induced changes in cloud cover dominate the climatic response and lead to an overall cooling by the biomass burning plumes.

We have monitored water vapor isotopes since January 2020 on Amsterdam Island in the Indian Ocean. We show 11 periods associated with abrupt negative excursions of water vapor δ¹⁸Ο. Six of these events show a decrease in gaseous elemental mercury, suggesting subsidence of air from a higher altitude. Accurately representing the water isotopic signal during these cold fronts is a real challenge for the atmospheric components of Earth system models equipped with water isotopes.

We have estimated the carbon monixide (CO) European emissions from satellite observations of the MOPITT instrument at the relatively high resolution of 0.5° for a period of over 10 years from 2011 to 2021. The analysis of the inversion results reveals the challenges associated with the inversion of CO emissions at the regional scale over Europe.

A new method, the geographical detector method (GDM), has been applied to satellite data, in addition to commonly used statistical methods, to study the sensitivity of cloud properties to aerosol over China. Different constraints for aerosol and cloud liquid water path apply over polluted and clean areas. The GDM shows that cloud parameters are more sensitive to combinations of parameters than to individual parameters, but confounding effects due to co-variation of parameters cannot be excluded.

By relying solely on publicly available media reports, we were able to infer the temporal evolution and the injection height for the Nord Stream gas leaks in September 2022. The inventory specifies locations, vertical distributions, and temporal evolution of the methane sources. The inventory can be used to simulate the event with atmospheric transport models. The inventory is supplemented with a set of observational data tailored to evaluate the results of the simulated atmospheric dispersion.

The transport history of tropospheric air masses above the tropical western Pacific is studied by local ozone and relative humidity profile measurements from Palau. A prominent anti-correlation between both tracers separates air masses of different origin and genesis. Back trajectories confirm a local convective origin of the year-round humid ozone-poor background. Anomalously dry ozone-rich air is generated in tropical Asia by pollution and dehydrated during transport via radiative cooling.

Mixing ratios of C₂-C₅ NMHCs and methanethiol were measured on an island in the Baltic Sea using an in situ gas chromatograph. Shipping emissions were found to be an important source of ethene, ethyne, propene, and benzene. High summertime mixing ratios of methanethiol and dependence of mixing ratios on seawater temperature and height indicated the biogenic origin to possibly be phytoplankton or macroalgae. These emissions may have a strong impact on SO₂ production and new particle formation.

This study evaluates the Geostationary Environment Monitoring Spectrometer (GEMS) HCHO product by comparing its vertical column densities (VCDs) with those of TROPOMI and ground-based observations. Based on some sensitivity tests, obtaining radiance references under clear-sky conditions significantly improves HCHO retrieval quality. GEMS HCHO VCDs captured seasonal and diurnal variations well during the first year of observation, showing consistency with TROPOMI and ground-based observations.

Cloud-radiative heating (CRH) affects extratropical cyclones but is uncertain in weather and climate models. We provide a framework to quantify uncertainties in CRH within an extratropical cyclone due to four factors and show that the parameterization of ice optical properties contributes significantly to uncertainty in CRH. We also argue that ice optical properties, by affecting CRH on spatial scales of 100 km, are relevant for the large-scale dynamics of extratropical cyclones.

Particles were collected during the flight campaign StratoClim 2017 within the Asian tropopause aerosol layer (ATAL). Refractory particles from seven different flights were characterized by scanning and transmission electron microscopy (SEM, TEM). The most abundant refractory particles are silicates and non-volatile organics. The most important sources are combustion processes at the ground and the agitation of soil material. During one flight, small cinnabar particles (HgS) were also detected.

Highly oxygenated organic molecules are important contributors to secondary organic aerosol. Their yield depends on detailed atmospheric chemical composition. One important parameter is the ratio of hydroperoxy radicals to organic peroxy radicals (HO₂/RO₂), and we show that higher HO₂/RO₂ ratios lower the secondary organic aerosol yield. This is of importance as laboratory studies are often biased towards organic peroxy radicals.

Secondary organic aerosols (SOAs) can exist in liquid, semi-solid, or amorphous solid states, which are rarely accounted for in current chemical transport models. We predict the phase state of SOA particles over China and find that in northwestern China SOA particles are mostly highly viscous or glassy solid. Our results indicate that the particle phase state should be considered in SOA formation in chemical transport models for more accurate prediction of SOA mass concentrations.

This study analyses three acute ozone episodes in Barcelona (NE Spain) which have occurred only in recent years and are of particular concern due to the city's significant population. The findings uncover a complex interplay of factors, notably shared among episodes, including pollution transport at different scales and specific weather and emission patterns. These insights significantly enhance our understanding of these occurrences and improve predictive capabilities.

On 15 January 2022, the Hunga Tonga-Hunga Ha‘apai volcano exploded in a vigorous eruption, causing many atmospheric phenomena reaching from the surface up to space. In this study, we investigate how the mesospheric winds were affected by the volcanogenic gravity waves and estimated their propagation direction and speed. The interplay between model and observations permits us to gain new insights into the vertical coupling through atmospheric gravity waves.

Four-year satellite observations of XCH₄ are used to derive CH₄ emissions in three regions of China’s coal-rich Shanxi province. The wind-assigned anomalies for two opposite wind directions are calculated, and the estimated emission rates are comparable to the current bottom-up inventory but lower than the CAMS and EDGAR inventories. This research enhances the understanding of emissions in Shanxi and supports climate mitigation strategies by validating emission inventories.

Ice-core nitrate could track the past atmospheric NO_x and oxidant level, but its interpretation is hampered by the post-depositional processing. In this work, an inverse model was developed and tested against two polar sites and was shown to well reproduce the observed nitrate signals in snow and atmosphere, suggesting that the model can properly correct for the effect of post-depositional processing. This model offers a very useful tool for future studies on ice-core nitrate records.

In our study we provide an assessment, through a sensitivity study, of the limitations of models to calculate the dust direct radiative effect (DRE) due to the underrepresentation of its size, refractive index (RI), and shape. Our results indicate the necessity of including more realistic sizes and RIs for dust particles in dust models, in order to derive better estimations of the dust direct radiative effects.

This source apportionment modeling study shows that around 70 % of ground-level O₃ in Madrid (Spain) is transported from other regions. Nonetheless, emissions from local sources, mainly road traffic, play a significant role, especially under atmospheric stagnation. Local measures during those conditions may be able to reduce O₃ peaks by up to 30 % and, thus, lessen impacts from high-O₃ episodes in the Madrid metropolitan area.

Using IASI global infrared measurements, we retrieve nitrous acid (HONO) in fire plumes from space. We detect large enhancements of pyrogenic HONO worldwide, especially from intense wildfires at Northern Hemisphere mid- and high latitudes. Predominance of IASI nighttime over daytime measurements sheds light on HONO's extended lifetime and secondary formation during long-range transport in smoke plumes. Our findings deepen the understanding of atmospheric HONO, crucial for air quality assessment.

The contrail formation potential and its tempo-spatial distribution are estimated for the North Atlantic flight corridor. Meteorological conditions of temperature and relative humidity are taken from the ERA5 re-analysis and IAGOS. Based on IAGOS flight tracks, crossing length, size, orientation, frequency of occurrence, and overlap of persistent contrail formation areas are determined. The presented conclusions might provide a guide for statistical flight track optimization to reduce contrails.

A new aerosol-type classification algorithm has been proposed. It includes an optical database built by Mie scattering and a complex refractive index working as a baseline to identify different aerosol types. The new algorithm shows high accuracy and efficiency. Hence, a global map of aerosol types was generated to characterize aerosol types across the five continents. It will help improve the accuracy of aerosol inversion and determine the sources of aerosol pollution.

Sulfate aerosol from the volcanic eruption at La Palma in 2021 was observed over Cabo Verde. We characterized the aerosol burden based on a case study of lidar and sun photometer observations. We compared the volcanic case to the typical background conditions (reference case) to quantify the volcanic pollution. We show the first ever measurements of the extinction coefficient, lidar ratio and depolarization ratio at 1064 nm for volcanic sulfate.

We quantify 2019 methane emissions in the contiguous US (CONUS) at a ≈ 25 km × 25 km resolution using satellite methane observations. We find a 13 % upward correction to the 2023 US Environmental Protection Agency (EPA) Greenhouse Gas Emissions Inventory (GHGI) for 2019, with large corrections to individual states, urban areas, and landfills. This may present a challenge for US climate policies and goals, many of which target significant reductions in methane emissions.

The stunning colors of the sky and clouds result from light scattering in the atmosphere, whose density changes with height. Previously, calculating these colors involves costly, sometimes inaccurate methods. This paper presents a silver bullet: a single elegant formula that simplifies these complex calculations. What is the result? We have faster, more precise predictions of atmospheric colors, from Earth's blue skies and red sunsets to Venus's golden hues.

Based on long-term observational, reanalysis, and numerical model simulation datasets from 1901 through 2014, this study shows that precipitation over the East Asian monsoon boundary zone featured prominent interdecadal changes, with dry summers during the periods preceding 1927, 1939–1945, 1968–1982, and 1998–2010 and wet summers during 1928–1938, 1946–1967, and 2011 onwards. The Indian Ocean basin mode is an important oceanic modulator responsible for its interdecadal variations.

The organic vapor condensation with water vapor (co-condensation) in rising air below clouds is modeled in this work over the boreal forest because the forest air is rich in organic vapors. We show that the number of cloud droplets can increase by 20 % if considering co-condensation. The enhancements are even larger if the air contains many small, naturally produced aerosol particles. Such conditions are most frequently met in spring in the boreal forest.

The results provide direct evidence of efficient droplet activation of black carbon (BC). The cloud condensation nuclei (CCN) activation fraction of BC was higher than for all particles, suggesting higher CCN activity of BC, even though its hygroscopicity is lower. Our research reveals that the evolution of BC's hygroscopicity and its CCN activation properties through atmospheric aging can be effectively characterized by the photochemical age.