Abstract. Atmospheric particles can impact cloud formation and play a critical role in regulating cloud properties. However, particle characteristics at the single-particle level and their ability to act as ice-nucleating particles (INPs) over the marine atmosphere are poorly understood. In this study, we present micro-spectroscopic characterizations and ice nucleation properties of particles collected

Abstract. This study investigates long-term trends of criteria air pollutants, including NO2, CO, SO2, O3 and PM2.5, and Ox (meaning NO2+O3) measured in 10 Canadian cities during the last 2 to 3 decades. We also investigated associated driving forces in terms of emission reductions, perturbations due to varying weather conditions and large-scale wildfires, as well as changes in O3 sources and sinks

Abstract. Atmospheric volatile organic compounds (VOCs) constitute a wide range of species, acting as precursors to ozone and aerosol formation. Atmospheric chemistry and transport models (CTMs) are crucial to understanding the emissions, distribution, and impacts of VOCs. Given the uncertainties in VOC emissions, lack of evaluation studies, and recent changes in emissions, this work adapts the European

Abstract. Water-insoluble organic carbon (WIOC) constitutes a substantial portion of organic carbon (OC) and contributes significantly to light absorption by brown carbon (BrC), playing pivotal roles in climate forcing. China is a hotspot region with high levels of OC and BrC, but information regarding the sources and light-absorbing properties of WIOC on a national scale remains scarce. Here, we investigated

Abstract. Projections of global climate change and Arctic amplification are sensitive to the representation of low-level cloud phase in climate models. Ice-nucleating particles (INPs) are necessary for primary cloud ice formation at temperatures above approximately -38 °C, and thus significantly affect cloud phase and cloud radiative effect. Due to their complex and insufficiently understood variability

Abstract. In 2020 the International Maritime Organization (IMO) implemented strict new regulations on the emissions of sulphate aerosol from the world's shipping fleet. This can be expected to lead to a reduction in aerosol-driven cooling, unmasking a portion of greenhouse gas warming. The magnitude of the effect is uncertain, however, due to the large remaining uncertainties in the climate response

Abstract. Simultaneous observations of airglow intensity, rotational temperature, and wind data at São João do Cariri (36.31° W; 07.40° S) by Co-located photometer, all-sky imager, and meteor radar were used to study the characteristics of vertical propagating gravity waves (GWs). Using the photometer data, the phase progression of GWs with the same propagation period in the OI 557.7nm, O2, NaD-line

Abstract. This study presents an updated evaluation of stratospheric ozone profile trends at Arosa/Davos/Hohenpeißenberg, Switzerland/Germany, Observatory de Haute Provence (OHP), France, Boulder, Colorado, Mauna Loa Observatory (MLO) and Hilo, Hawaii, and Lauder, New Zealand with focus on the ozone recovery period post 2000. Trends are derived using vertical ozone profiles from NOAA’s Dobson Network

Abstract. Extreme bushfire events amplify climate change by emitting greenhouse gases and destroying carbon sinks while causing economic damage through property destruction and even fatalities. One such bushfire occurred in Australia during 2019/2020, injecting large amounts of aerosols and gases into the stratosphere and depleting the ozone layer. While previous studies focused on the drivers behind

Abstract. Global-mean surface temperature rapidly increased 0.27 ± 0.05 K from 2022 to 2023. Such an interannual global warming spike is not unprecedented in the observational record with previous instances occurring in 1956–57 and 1976–77. However, why global warming spikes occur is unknown and the rapid global warming of 2023 has led to concerns that it could have been externally driven. Here we

Abstract. Tropical precipitation cluster area and intensity distributions follow power laws, but the physical processes responsible for this macroscopic behavior remain unknown.We analyze global simulations at ten-kilometer horizontal resolution that are configured to have drastically varying degrees of realism, ranging from global radiative-convective equilibrium to fully realistic atmospheric simulations

Abstract. This study investigated the effect of relative humidity (RH) on the chemical composition of gas and particle phases formed from the photooxidation of 1,3-butadiene (13BD) in the presence of NOx under acidic and non-acidic conditions. The experiments were conducted in a 14.5 m3 smog chamber operated in a steady-state mode. Products were identified by high performance liquid chromatography

Abstract. Global crude steel production is expected to continue to increase in the coming decades to meet the demands of the growing world population. Currently, the dominant steelmaking technology worldwide is the conventional highly CO2-intensive blast furnace–basic oxygen furnace production route (also known as the Linz–Donawitz process), which uses iron ore as raw material and coke as a reducing

Abstract. High contents of reactive nitrogen components aggravate air pollution and could also impact ecosystem structures and functioning across the terrestrial–aquatic–marine continuum. However, the long-term historical trends and future predictions of reactive nitrogen components at the global scale still remain highly uncertain. In our study, field observations, satellite products, model outputs

Abstract. Nitrogen oxides (NOx = NO + NO2) are air pollutants which are co-emitted with CO2 during high-temperature combustion processes. Monitoring NOx emissions is crucial for assessing air quality and for providing proxy estimates of CO2 emissions. Satellite observations, such as those from the TROPOspheric Monitoring Instrument (TROPOMI) on board the Sentinel-5P satellite, provide global coverage

Abstract. During the warm months of the year in Catalonia, the marine air overcomes the coastal mountain range and reaches the eastern Ebro sub-basin. This phenomenon is called marinada and has recently been thoroughly characterized for the first time by Jiménez et al. (2023), based on surface climatological data. However, the main physical mechanisms involved in its arrival and propagation remain

Abstract. This study investigated the potential effects of changes in inorganics on aerosol water uptake and, thus, on secondary organic aerosol (SOA) formation in wintertime haze based on the size-resolved measurements of non-refractory fine particulate matter (NR-PM2.5) in Xi'an, northwestern China. The composition of inorganic aerosol showed significant changes in winter 2018–2019 compared to winter

Abstract. To investigate the historical levels of atmospheric ammonia (NH3) pollution in south-eastern Europe, a 182 m long ice core was extracted from Mount Elbrus in the Caucasus, Russia. This ice core contains a record of ammonium (NH4+) levels from ~1750 CE (Common Era) to 2009 CE. The NH4+ ice core record indicates a 3.5-fold increase of annual concentrations from 34 ± 7 ng g-1 (~1750–1830) to

Abstract. The carbon uptake period (CUP) refers to the time of each year during which the rate of photosynthetic uptake surpasses that of respiration in the terrestrial biosphere, resulting in a net absorption of CO2 from the atmosphere to the land. Since climate drivers influence both photosynthesis and respiration, the CUP offers valuable insights into how the terrestrial biosphere responds to climate

Abstract. Atmospheric aerosol particles span orders of magnitude in size. In ultrafine particles, the energetic contributions of surfaces and interfaces to the Gibbs energy become significant and increase in importance as particle diameter decreases. For these particles, the thermodynamic equilibrium state depends on size, composition, and temperature. Various aerosol systems have been observed to

Abstract. The number of wildfire smoke layers in the upper troposphere per fire season increased at mid and high northern latitudes during the last years. To consider smoke in weather and climate models appropriately, the influence of smoke on a variety of atmospheric processes needs to be explored in detail. In this study, we focus on the potential impact of wildfire smoke on cirrus formation. For

Abstract. A simulation study on the impact of wildfire smoke (aged organic aerosol particles) on cirrus formation in the central Arctic is presented. The simulations in this part 2 of a series of two articles complement the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) field observations, presented and discussed in part 1. The measurements were performed with lidar

Abstract. Tropopause-overshooting convection in the midlatitudes provides a rapid transport pathway for air from the lower troposphere to reach the upper troposphere and lower stratosphere (UTLS) and can result in the formation of above-anvil cirrus plumes (AACPs) that significantly hydrate the stratosphere. Such UTLS composition changes alter the radiation budget and impact climate. Novel in situ

Abstract. Humic-like substances (HULIS) are complex macromolecules in water-soluble organic compounds (WSOCs) containing multiple functional groups, and transition metal ions (TMs) are ubiquitous in atmospheric particles. In this study, potential physical and chemical interactions between HULIS and four TM species, including Cu2+, Mn2+, Ni2+, and Zn2+, were analyzed by optical method under acidic,

Abstract. The supercooled liquid fraction (SLF) in mixed-phase clouds (MPCs) is an essential variable of cloud microphysical processes and climate sensitivity. However, the SLF is currently calculated in spaceborne remote sensing only as the cloud phase–frequency ratio of adjacent pixels, which results in a loss of the original resolution in observations of cloud liquid or ice content within MPCs.

Abstract. Within the TURBAN project, a "Legerova campaign" focusing on air quality and meteorology in the traffic-loaded part of the Prague city (Czech Republic) was carried out from 30 May 2022 to 28 March 2023. The network comprised of 20 combined low-cost sensor (LCS) stations for NO2, O3, PM10 and PM2.5 concentrations, along with a mobile meteorological mast, a single-channel microwave radiometer

Abstract. The accelerated warming of the Arctic manifests in sea ice loss and melting glaciers, significantly altering the dynamics of marine biota. This disruption in marine ecosystems can lead to the emission of biological ice nucleating particles (INPs) from the ocean into the atmosphere. Once airborne, these INPs induce cloud droplet freezing, thereby affecting cloud lifetime and radiative properties

Abstract. The southeast Atlantic region, characterized by persistent stratocumulus clouds, has one of the highest uncertainties in aerosol radiative forcing and significant variability across climate models. In this study, we analyze the seasonally varying role of marine aerosol sources and identify key uncertainties in aerosol composition at cloud-relevant altitudes over the southeast Atlantic using

Abstract. Since the launch of TROPOMI on the Sentinel-5 Precursor (S5P) satellite, NO2 observations have become available with a resolution of 3.5× 5 km, which makes monitoring NOx emissions possible at the scale of city districts and industrial facilities. For Europe, emissions are reported on an annual basis for country totals and large industrial facilities and made publicly available via the European

Abstract. The chemical composition of the upper troposphere/lower stratosphere region (UTLS) is influenced by horizontal transport of air masses, vertical transport within convective systems and warm conveyor belts, rapid turbulent mixing, as well as photochemical production or loss of species. This results in the formation of the extratropical transition layer (ExTL), which is defined by the vertical

Abstract. The Asian summer monsoon has a strong convectional component with which aerosols are able to be lifted up into the lower stratosphere. Due to usually long lifetimes and long-range transport aerosols remain there much longer than in the troposphere and are also able to be advected around the globe. Our aim of this study is a synergy between simulations by Chemical Lagrangian Model of the Stratosphere

Abstract. The Hunga volcano violently erupted on January 15th, 2022, and produced the largest stratospheric aerosol layer perturbation of the last 30 years. One notable effect of the Hunga eruption was the significant modification of the size distribution (SD) of the stratospheric aerosol layer with respect to background conditions and other recent moderate stratospheric eruptions, with larger mean

Abstract. Nitrate (NO3-) aerosol is projected to increase dramatically in the coming decades and may become the dominant inorganic particle species. This is due to the continued strong decrease in SO2 emissions, which is not accompanied by a corresponding decrease in NOx and especially NH3 emissions. Thus, the radiative effect (RE) of NO3- aerosol may become more important than that of SO42- aerosol

Abstract. The quasi-biennial oscillation (QBO) in tropical winds perturbs stratospheric ozone throughout much of the atmosphere via changes in transport of ozone and other trace gases and via temperature changes that alter chemical processes. Here we separate the temperature-driven changes using the Department of Energy’s Energy Exascale Earth System Model version 2 (E3SMv2) with linearized stratospheric

Abstract. Non-methane volatile organic compounds (NMVOC), serving as crucial precursors of O3, have a significant impact on atmospheric oxidative capacity and O3 formation. However, both anthropogenic and biogenic NMVOC emissions remain subject to considerable uncertainty. Here, we extended the Regional multi-Air Pollutant Assimilation System (RAPAS) using the ensemble Kalman filter (EnKF) algorithm

Abstract. Ozone (O3) pollution is posing significant challenges to urban air quality improvement in China. The formation of surface O3 is intricately linked to chemical reactions which are influenced by both meteorological conditions and local emissions of precursors (i.e., NOx and VOCs). The atmospheric environment capacity decreases when meteorological conditions deteriorate, resulting in the accumulation

Abstract. Biomass burning releases large amounts of aerosols and chemical species into the atmosphere, representing a major source of air pollutants. Emissions and by-products can be transported over long distances, presenting challenges in quantification. This is mainly done using satellites, which offer global coverage and data acquisition for places that are difficult to access. In this study, ground-based

Abstract. Naphthalene (Nap) and its derivatives, including 1-methylnaphthalene (1-MN) and 2-methylnaphthalene (2-MN), serve as prominent intermediate volatile organic compounds (IVOCs) and contribute to the formation of secondary organic aerosol (SOA). In this study, the Community Multiscale Air Quality (CMAQ) model coupled with detailed emissions and reactions of these compounds was utilized to examine

Abstract. Aviation is currently estimated to contribute ~3.5 % of the net anthropogenic effective radiative forcing (ERF) of Earth's atmosphere. The largest component of this forcing comes from contrail cirrus (also with a large associated uncertainty of ~70 %), estimated to be two times larger than the contribution from aviation CO2 emissions. Here we implement the contrail parameterisation previously

Abstract. In this study, we present real-time measurements of organic aerosol (OA) and biogenic volatile organic compounds (BVOCs) at a pine forest stressed by bark beetles and previous droughts close to a biogas power plant (BPP) in western Germany during June 2020. A proton-transfer-reaction time-of-flight mass spectrometer coupled with a particle inlet (CHARON-PTR-ToF-MS) and a Vocus-PTR-ToF-MS

Abstract. The propagation of gravity waves (GW) and their role in the coupling of the troposphere–stratosphere–mesosphere atmospheric layers during sudden stratospheric warming (SSW) are studied. A standard set of hydrodynamic equations (HD) is used to derive the analytical dispersion equations and the GWs reflection coefficient. These equations are applied to the troposphere–stratosphere and stratosphere–mesosphere

Abstract. Quantifying global cloud condensation nuclei (CCN) concentrations is crucial for reducing uncertainties in radiative forcing resulting from aerosol-cloud interactions. This study analyzes two novel, independent, open-source global CCN datasets derived from spaceborne Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements and Copernicus Atmosphere Monitoring Service (CAMS)

Abstract. Aerosols play a critical role in the Arctic’s radiative balance, influencing solar radiation and cloud formation based on their physicochemical properties (e.g., size, abundance, and chemical composition). Limited observations in the central Arctic leave gaps in understanding aerosol dynamics year-round, affecting model predictions of climate-relevant properties. Here, we present the first

Abstract. Mineralogical composition drives dust impacts on Earth's climate systems. However, most climate models still use homogeneous dust, without accounting for the temporal and spatial variation in mineralogy. To quantify the radiative impact of resolving dust mineralogy on Earth's climate, we implement and simulate the distribution of dust minerals (i.e., illite, kaolinite, smectite, hematite

Abstract. The tropical tropopause layer (TTL) is the main gateway for air transiting from the troposphere to the stratosphere and therefore impacts the chemical composition of the stratosphere. In particular, the cold-point tropopause, where air parcels encounter their final dehydration, effectively controls the water vapor content of the lower stratosphere. Given the important role of stratospheric

Abstract. Aerosol vertical profile measurements were made using multi-axis differential optical absorption spectroscopy (MAX-DOAS) and mini-Micropulse LiDAR (MPL) at One Tree Island in the Southern Great Barrier Reef from February to April 2023. This is an understudied location in terms of atmospheric aerosols and chemistry but is growing in importance as multiple research streams examine the influence

Abstract. The age of air is an important transport diagnostic that can be derived from trace gas measurements and compared to global chemistry climate model output. We describe a new technique to calculate the age of air, measuring transport times from the Earth’s surface to any location in the atmosphere based on simultaneous in situ measurements of multiple key long-lived trace gases. The primary

Abstract. Stable nitrogen isotopic composition (δ15N) has proven to be a valuable tool for identifying sources of nitrates (NO3–) in PM2.5. However, the absence of a systematic study on the δ15N values of domestic NOx sources hinders accurate identification of NO3– sources in China. Here, we systematically determined and refined δ15N values for six categories of NOx sources in the local Tianjin area

Abstract. Climate extremes are projected to cause unprecedented deviations in the emission and transformation of volatile organic compounds (VOCs), which trigger feedback mechanisms that will impact the atmospheric oxidation and formation of aerosols and clouds. However, the response of VOCs to future conditions such as extreme heat and wildfire events is still uncertain. This study explored the modification

Abstract. Increased surface warming over the Arctic, triggered by increased greenhouse gas concentrations and feedback processes in the climate system, has been causing a steady decline in sea-ice extent and thickness. With the retreating sea-ice, shipping activity will likely increase in the future driven by economic activity and the potential for realizing time and fuel savings from transiting shorter

Abstract. The thermodynamic phase of clouds in low and middle levels over the Southern Ocean and the Arctic marine regions is poorly known, leading to uncertainties in the radiation budget in weather and climate models. To improve the knowledge of the cloud phase, we analyse 2 years of the raDAR-liDAR (DARDAR) dataset based on active satellite instruments. We classify clouds according to their base

Abstract. Cold extremes have large impacts on human society. Understanding the physical processes dominating the changes in cold extremes is crucial for a reliable projection of future climate change. The observed cold extremes have decreased during the last several decades, and this trend will continue under future global warming. Here, we quantitatively identify the contributions of dynamic (changes

Abstract. General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the climate by aerosol–cloud interactions (ERFaci). The discrepancy is thought to stem in part from GCMs' inability to represent the turbulence–microphysics

Abstract. Anthropogenic mercury (Hg) emissions to the atmosphere are a long-lived hazard to human and environmental health. The UN Minamata Convention on Mercury is seeking to lower anthropogenic mercury emissions through a mix of policies from banning certain Hg uses to reducing unintentional Hg release from different activities. In addition to independent Hg policy, strategies to mitigate greenhouse

Abstract. Wildfires release large amounts of greenhouse gases into the atmosphere, exacerbating climate change and causing severe impacts on air quality and human health. Including carbon dioxide (CO2) emissions from wildfires in international assessments and national emission reduction responsibilities is crucial for global carbon reduction and environmental governance. In this study, based on a bottom-up

Abstract. Hydrofluorocarbons (HFCs) are powerful anthropogenic greenhouse gases (GHGs) with high global-warming potentials (GWPs). They have been widely used as refrigerants, insulation foam-blowing agents, aerosol propellants, and fire suppression agents. Since the mid-1990s, emissions of HFCs have been increasing rapidly as they are used in many applications to replace ozone-depleting chlorofluorocarbons

Abstract. Atmospheric radiative transfer models are extensively used in Earth observation to simulate radiative processes occurring in the atmosphere and to provide both upwelling and downwelling synthetic brightness temperatures for ground-based, airborne, and satellite radiometric sensors. For a meaningful comparison between simulated and observed radiances, it is crucial to characterize the uncertainty

Abstract. The capacity of particulate matter (PM) to generate reactive oxygen species (ROS) in vivo leading to oxidative stress is thought to be a main pathway in the health effects of PM inhalation. Exogenous ROS from PM can be assessed by acellular oxidative potential (OP) measurements as a proxy of the induction of oxidative stress in the lungs. Here, we investigate the importance of OP apportionment

Abstract. Brown carbon aerosol (BrC) is one major contributor to atmospheric air pollution in Europe, especially in winter. Therefore, we studied the chemical composition, diurnal variation, and sources of BrC from 17th February to 16th March at a rural location in southwest Germany. In total, 178 potential BrC molecules (including 7 nitro aromatic compounds, NACs) were identified in the particle phase

Abstract. Reliable attribution of Asian summer monsoon variations to aerosol forcing is critical to reducing uncertainties in future projections of regional water availability, which is of utmost importance for risk management and adaptation planning in this densely populated region. Yet, simulating the monsoon remains a challenge for climate models that suffer from long-standing biases, undermining