Arctic warming by abundant fine sea salt aerosols from blowing snow

The Arctic warms nearly four times faster than the global average, and aerosols play an increasingly important role in Arctic climate change. In the Arctic, sea salt is a major aerosol component in terms of mass concentration during winter and spring. However, the mechanisms of sea salt aerosol production remain unclear. Sea salt aerosols are typically thought to be relatively large in size but low in number concentration, implying that their influence on cloud condensation nuclei population and cloud properties is generally minor. Here we present observational evidence of abundant sea salt aerosol production from blowing snow in the central Arctic. Blowing snow was observed more than 20% of the time from November to April. The sublimation of blowing snow generates high concentrations of fine-mode sea salt aerosol (diameter below 300 nm), enhancing cloud condensation nuclei concentrations up to tenfold above background levels. Using a global chemical transport model, we estimate that from November to April north of 70° N, sea salt aerosol produced from blowing snow accounts for about 27.6% of the total particle number, and the sea salt aerosol increases the longwave emissivity of clouds, leading to a calculated surface warming of +2.30 W m−2 under cloudy sky conditions

Intercomparison of airborne and surface-based measurements during the CLARIFY, ORACLES and LASIC field experiments

This is the final version. Available on open access from the European Geosciences Union via the DOI in this recordCode availability: Processing code for the FAAM core measurements suite is available from GitHub (Sproson et al., 2020).Data availability Airborne data for the CLARIFY campaign are available from the Centre for Environmental Data Analysis (Facility for Airborne Atmospheric Measurements et al., 2017) and for the ORACLES campaign from NASA Earth Science Project Office (ORACLES Science Team, 2020). The LASIC ground-based data sets are publicly available from the Atmospheric Radiation Measurement Climate Research Facility (Zuidema et al., 2017) with specialist data sets available for the following: SP2 – https://iop.archive.arm.gov/arm-iop/2016/ (last access: 25 October 2022, Sedlacek, 2017), CO – https://doi.org/10.5439/1046183 (Springston, 2018b), CAPS PMSSA – https://adc.arm.gov/discovery/#/results/s::caps-ssa (Onasch et al., 2015), ACSM – https://doi.org/10.5439/1763029 (Zawadowicz and Howie, 2021).Data are presented from intercomparisons between two research aircraft, the FAAM BAe-146 and the NASA Lockheed P3, and between the BAe-146 and the surface-based DOE (Department of Energy) ARM (Atmospheric Radiation Measurement) Mobile Facility at Ascension Island (8∘ S, 14.5∘ W; a remote island in the mid-Atlantic). These took place from 17 August to 5 September 2017, during the African biomass burning (BB) season. The primary motivation was to give confidence in the use of data from multiple platforms with which to evaluate numerical climate models. The three platforms were involved in the CLouds–Aerosol–Radiation Interaction and Forcing for Year 2017 (CLARIFY-2017), ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES), and Layered Atlantic Smoke and Interactions with Clouds (LASIC) field experiments. Comparisons from flight segments on 6 d where the BAe-146 flew alongside the ARM facility on Ascension Island are presented, along with comparisons from the wing-tip-to-wing-tip flight of the P3 and BAe-146 on 18 August 2017. The intercomparison flight sampled a relatively clean atmosphere overlying a moderately polluted boundary layer, while the six fly-bys of the ARM site sampled both clean and polluted conditions 2–4 km upwind. We compare and validate characterisations of aerosol physical, chemical and optical properties as well as atmospheric radiation and cloud microphysics between platforms. We assess the performance of measurement instrumentation in the field, under conditions where sampling conditions are not as tightly controlled as in laboratory measurements where calibrations are performed. Solar radiation measurements compared well enough to permit radiative closure studies. Optical absorption coefficient measurements from all three platforms were within uncertainty limits, although absolute magnitudes were too low (<10 Mm−1) to fully support a comparison of the absorption Ångström exponents. Aerosol optical absorption measurements from airborne platforms were more comparable than aircraft-to-ground observations. Scattering coefficient observations compared adequately between airborne platforms, but agreement with ground-based measurements was worse, potentially caused by small differences in sampling conditions or actual aerosol population differences over land. Chemical composition measurements followed a similar pattern, with better comparisons between the airborne platforms. Thermodynamics, aerosol and cloud microphysical properties generally agreed given uncertainties.Natural Environment Research Council (NERC)NERC/Met Office Industrial Case studentshipResearch Council of NorwayUS Department of Energy, Office of ScienceNASAUS Department of Energy Atmospheric Systems Research (ASR) programm

Improved identification of primary biological aerosol particles using single particle mass spectrometry

This dataset contains data used to generate figures in the journal article "Improved identification of primary biological aerosol particles using single particle mass spectrometry" published in Atmospheric Chemistry and Physics. Data is provided in .csv format with column headers as variable names

Physicochemical properties of charcoal aerosols derived from biomass pyrolysis affect their ice-nucleating abilities at cirrus and mixed-phase cloud conditions

Atmospheric aerosol particles play a key role in air pollution, health, and climate. Particles from biomass burning emissions are an important source of ambient aerosols, have increased over the past few decades, and are projected to further surge in the future as a result of climate and land use changes. Largely as a result of the variety of organic fuel materials and combustion types, particles emitted from biomass burning are often complex mixtures of inorganic and organic materials, with soot, ash, and charcoal having previously been identified as main particle types being emitted. Despite their importance for climate, their ice nucleationactivities remain insufficiently understood, in particular for charcoalparticles, whose ice nucleation activity has not been reported. Here, wepresent experiments of the ice nucleation activities of 400 nm size-selected charcoal particles, derived from the pyrolysis of two different biomass fuels, namely a grass charcoal and a wood charcoal. We find that the pyrolysis-derived charcoal types investigated do not contribute to ice formation via immersion freezing in mixed-phase cloud conditions. However, our results reveal considerable heterogeneous ice nucleation activity of both charcoal types at cirrus temperatures. An inspection of the ice nucleation results together with dynamic vapor sorption measurements indicates that cirrus ice formation proceeds via pore condensation and freezing. We find wood charcoal to be more ice-active than grass charcoal at cirrus temperatures. We attribute this to the enhanced porosity and water uptake capacity of the wood compared to the grass charcoal. In support of the results, we found a positive correlation of the ice nucleation activity of the wood charcoal particles and their chemical composition, specifically the presence of (inorganic) mineral components, based on single-particle mass spectrometry measurements. Even though correlational in nature, our results corroborate recent findings that ice-active minerals could largely govern the aerosol-cloud interactions of particles emitted from biomass burning emissions.ISSN:1680-7375ISSN:1680-736

CCN and INP activity of middle eastern soil dust

The term mineral dust encompasses a myriad of particle compositions from both fertile and arid regions. Due to this diversity, the quantitative understanding of mineral dust as Cloud Condensation Nuclei (CCN) and Ice Nucleating Particles (INPs) in the Earth’s atmosphere demand further investigation. This study characterizes the CCN and INP activity of mineral dust particles from samples collected from one of the Earth’s major arid regions, Saudi Arabia. Samples were size selected at particle diameters (Dp) of 300, 700, and 950 nm and introduced into a Cloud Condensation Nuclei Counter (CCNC) and a SPectrometer for Ice Nuclei (SPIN) chamber to investigate cloud nucleation activity. The chemical composition of the particles was analyzed with laser mass spectrometry and mineralogical information was provided by polarized light microscopy. Transmission electron microscopy was used to ascertain particle morphology. Each particle size was exposed to water supersaturations of 0.06–1.0% in the CCNC and to ice supersaturation ratios of 1.1 to 1.5 at temperatures from −25 to −42 °C in SPIN. The CCN activity ranged from hygroscopicity values (κ) of 0.001 to 0.01. This is towards the lower range of critical supersaturations found for other mineral dust samples from e.g. the Sahara, North Africa, China and Asia. The INP activity, defined by fractional activation and supersaturation at the onset of ice nucleation was in the range of other natural mineral dusts (e.g., the Sahara, Canary Islands), and somewhat lower than industrially processed Arizona Test Dust. This study highlights the importance of considering size-resolved compositional data when interpreting the cloud-nucleation activity of natural mineral and soil dusts.ISSN:1875-963

Molecular Characterization of Organosulfate-Dominated Aerosols over Agricultural Fields from the Southern Great Plains by High-Resolution Mass Spectrometry

The molecular composition of organic aerosols, especially for day/nighttime variations of organosulfates above agricultural fields, is not well understood despite profound impacts on regional climate, crop production, air quality, and human health. Here, nanospray desorption electrospray ionization with high-resolution mass spectrometry (nano-DESI-HRMS) is used to interrogate the molecular composition of organic aerosols collected at the Southern Great Plains, located in an agricultural region of Oklahoma. Identified molecular formulae featured carbon, hydrogen, oxygen (CHO), nitrogen (CHNO), and/or sulfur (CHOS, CHNOS), with higher organosulfate proportions during daytime (41%) compared to nighttime (30%). Nighttime aerosols featured increases in CHO, CHNO, and extremely low volatility organic carbon (ELVOC) species. However, due to high relative humidity, the nighttime aerosols phase state was found to be more liquid-like than daytime aerosols using parametrized glass transition temperatures. Aerosol molecular composition from an anthropogenically influenced plume (southerly winds) showed significant increases in CHOS and ELVOC species. By comparison with chamber studies, CHOS species are suspected to be of mixed biogenic and anthropogenic origin, whereas CHNOS species (not identified in the southerly winds) are suggested to predominately be of biogenic origin. Overall, this study provides key insight into organosulfates above agricultural fields, demonstrating dependence upon day/night cycles and episodic anthropogenic emissions

Aircraft measurements of aerosol and trace gas chemistry in the eastern North Atlantic

The Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA) investigated properties of aerosols and subtropical marine boundary layer (MBL) clouds. Low subtropical marine clouds can have a large effect on Earth's radiative budget, but they are poorly represented in global climate models. In order to understand their radiative effects, it is imperative to understand the composition and sources of the MBL cloud condensation nuclei (CCN). The campaign consisted of two intensive operation periods (IOPs) (June-July 2017 and January-February 2018) during which an instrumented G-1 aircraft was deployed from Lajes Field on Terceira Island in the Azores, Portugal. The G-1 conducted research flights in the vicinity of the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) atmospheric observatory on Graciosa Island. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and Ionicon proton-transfer-reaction mass spectrometer (PTR-MS) were deployed aboard the aircraft, characterizing chemistry of non-refractory aerosol and trace gases, respectively. The eastern North Atlantic region was found to be very clean, with an average non-refractory submicrometer aerosol mass loading of 0.6 mu g m(-3) in the summer and 0.1 mu g m(-3) in the winter, measured by the AMS. Average concentrations of the trace reactive gases methanol and acetone were 1-2 ppb; benzene, toluene and isoprene were even lower, <1 ppb. Mass fractions of sulfate, organics, ammonium and nitrate in the boundary layer were 69 %, 23 %, 7 % and 1 % and remained largely similar between seasons. The aerosol chemical composition was dominated by sulfate and highly processed organics. Particulate methanesulfonic acid (MSA), a well-known secondary biogenic marine species, was detected, with an average boundary layer concentration of 0.021 mu g m(-3), along with its gas-phase precursor, dimethyl sulfide (DMS). MSA accounted for no more than 3 % of the submicron, non-refractory aerosol in the boundary layer. Examination of vertical profiles of aerosol and gas chemistry during ACE-ENA reveals an interplay of local marine emissions and long-range-transported aged aerosol. A case of transport of biomass burning emissions from North American fires has been identified using back-trajectory analysis. In the summer, the non-refractory portion of the background CCN budget was heavily influenced by aerosol associated with ocean productivity, in particular sulfate formed from DMS oxidation. Episodic transport from the continents, particularly of biomass burning aerosol, periodically increased CCN concentrations in the free troposphere. In the winter, with ocean productivity lower, CCN concentrations were overall much lower and dominated by remote transport. These results show that anthropogenic emissions perturb CCN concentrations in remote regions that are sensitive to changes in CCN number and illustrate that accurate predictions of both transport and regional aerosol formation from the oceans are critical to accurately modeling clouds in these regions

Aircraft Measurements of Aerosol and Trace Gas Chemistry in the Eastern North Atlantic

The Aerosol and Cloud Experiment in the Eastern North Atlantic (ACE-ENA) investigated properties of aerosols and subtropical marine boundary layer (MBL) clouds. Low subtropical marine clouds can have a large effect on Earth s radiative budget, but they are poorly represented in global climate models. In order to understand their radiative effects, it is imperative to understand the composition and sources of the MBL cloud condensation nuclei (CCN). The campaign consisted of two intensive operation periods (IOPs) (June-July 2017 and January-February 2018) during which an instrumented G-1 aircraft was deployed from Lajes Field on Terceira Island in the Azores, Portugal. The G-1 conducted research flights in the vicinity of the Atmospheric Radiation Measurement (ARM) Eastern North Atlantic (ENA) atmospheric observatory on Graciosa Island. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and Ionicon protontransfer- reaction mass spectrometer (PTR-MS) were deployed aboard the aircraft, characterizing chemistry of nonrefractory aerosol and trace gases, respectively. The eastern North Atlantic region was found to be very clean, with an average non-refractory submicrometer aerosol mass loading of 0.6 µg m-3 in the summer and 0.1 µg m-3 in the winter, measured by the AMS. Average concentrations of the trace reactive gases methanol and acetone were 1-2 ppb; benzene, toluene and isoprene were even lower, \u3c 1 ppb. Mass fractions of sulfate, organics, ammonium and nitrate in the boundary layer were 69 %, 23 %, 7% and 1% and remained largely similar between seasons. The aerosol chemical composition was dominated by sulfate and highly processed organics. Particulate methanesulfonic acid (MSA), a well-known secondary biogenic marine species, was detected, with an average boundary layer concentration of 0.021 µg m-3, along with its gas-phase precursor, dimethyl sulfide (DMS). MSA accounted for no more than 3% of the submicron, non-refractory aerosol in the boundary layer. Examination of vertical profiles of aerosol and gas chemistry during ACE-ENA reveals an interplay of local marine emissions and long-range-transported aged aerosol. A case of transport of biomass burning emissions from North American fires has been identified using back-trajectory analysis. In the summer, the non-refractory portion of the background CCN budget was heavily influenced by aerosol associated with ocean productivity, in particular sulfate formed from DMS oxidation. Episodic transport from the continents, particularly of biomass burning aerosol, periodically increased CCN concentrations in the free troposphere. In the winter, with ocean productivity lower, CCN concentrations were overall much lower and dominated by remote transport. These results show that anthropogenic emissions perturb CCN concentrations in remote regions that are sensitive to changes in CCN number and illustrate that accurate predictions of both transport and regional aerosol formation from the oceans are critical to accurately modeling clouds in these regions