Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA)

Wang, Jian; Wood, R.; Jensen, Michael P.; Liu, Yangang; Lamer, Katia; Desai, Neel; Giangrande, Scott; Knopf, D. A.; Kollias, Pavlos; Laskin, Alexander; Liu, Xiaohong; Lu, Chen; Mechem, David B.; Mei, Fan; Starzec, Mariusz; Tomlinson, Jason; Yum, Seong Soo; Zheng, Guangjie; Aiken, A. C.; Azevedo, Eduardo Brito de; Blanchard, Yann; China, Swarup; Dong, Xiquan; Gallo, Francesca; Gao, Sinan; Ghate, Virendra P.; Glienke, Susanne; Goldberger, Lexie; Hardin, Joseph; Kuang, Chongai; Luke, E. P.; Matthews, Alyssa; Miller, Mark A.; Moffet, Ryan C.; Pekour, Mikhail; Schmid, Beat; Sedlacek, Arthur J.; Shaw, Raymond A.; Shilling, John E.; Sullivan, A.; Suski, Kaitlyn J.; Veghte, Daniel P.; Weber, R. J.; Wyant, M. C.; Yeom, Jaemin; Zawadowicz, Maria A.; Zhang, Zhibo

doi:10.1175/bams-d-19-0220.1

Cited by 52 publications

(63 citation statements)

References 124 publications

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“…The aerosol particles were sampled using an isokinetic inlet that has a 50 % upper cutoff size of 5 µm (Schmid et al, 2014) and were subsequently dried with a Nafion tube. Aerosol size distributions from 10 to ∼ 600 nm were measured by a fast-integrated mobility spectrometer (FIMS) (Wang et al, 2018). The total number concentration of particles larger than 10 nm in diameter (N >10 ) was measured by a condensation particle counter (CPC 3772, TSI Inc.).…”

Section: Measurement Overviewmentioning

confidence: 99%

Vertical profiles of trace gas and aerosol properties over the eastern North Atlantic: variations with season and synoptic condition

et al. 2021

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Abstract. Because of their extensive coverage, marine low clouds greatly impact the global climate. Presently, the response of marine low clouds to the changes in atmospheric aerosols remains a major source of uncertainty in climate simulations. One key contribution to this large uncertainty derives from the poor understanding of the properties and processes of marine aerosols under natural conditions and the perturbation by anthropogenic emissions. The eastern North Atlantic (ENA) is a region of persistent but diverse subtropical marine boundary layer (MBL) clouds, where cloud albedo and precipitation are highly susceptible to perturbations in aerosol properties. Here we examine the key processes that drive the cloud condensation nuclei (CCN) population in the MBL using comprehensive characterizations of aerosol and trace gas vertical profiles during the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) field campaign. During ACE-ENA, a total of 39 research flights were conducted in the Azores: 20 during summer 2017 and 19 during winter 2018. During summer, long-range-transported aerosol layers were periodically observed in the lower free troposphere (FT), leading to elevated FT CCN concentrations (NCCN). Both biomass burning and pollution from North America contribute to submicron aerosol mass in these layers, with pollution likely the dominant contributor. In contrast, long-range transported continental emissions have a much weaker influence on the aerosol properties in the ENA during the winter season. While the entrainment of FT air is a major source of particle number in the MBL for both seasons, on average it does not serve as a direct source of CCN in the MBL because the average FT NCCN is the same or even lower than that in the MBL. The particle number flux due to FT entrainment is dominated by pre-CCN (particles that are too small to form cloud droplets under typical conditions, i.e., particles with sizes below the Hoppel minimum) due to the elevated Npre-CCN in the lower FT. Once these pre-CCN are entrained into the MBL, they can grow and reach CCN size range through condensational growth, representing an indirect and major source of MBL CCN in the ENA. The impact of synoptic conditions on the aerosol properties is examined. Under pre-front and post-front conditions, shallow convective activity often leads to a deep and decoupled boundary layer. Coalescence scavenging and evaporation of drizzle below clouds lead to reduced NCCN and larger accumulation-mode particle sizes in the upper cloud-containing decoupled layer, indicating that surface measurements overestimate the NCCN relevant to the formation of MBL clouds under decoupled conditions.

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Section: Measurement Overviewmentioning

confidence: 99%

Vertical profiles of trace gas and aerosol properties over the eastern North Atlantic: variations with season and synoptic condition

et al. 2021

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“…2.3. Aerosols are simulated using the Modal Aerosol Model with four modes (MAM4) (Liu et al, 2016) coupled with Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) (Zaveri et al, 2008(Zaveri et al, , 2021Lu et al, 2021), for sulfate (SO4 2-), ammonium (NH4 + ), nitrate (NO3 -), primary organic matters (POM), SOA, sea salt, and mineral dust. MAM4 classifies aerosols into three size-dependent modes (Aitken, accumulation, and coarse) with an additional primary carbon mode for handling the aging of fine POM and black carbon (BC).…”

Section: Model Configurationmentioning

confidence: 99%

“…MAM4 defines the cut-off size ranges of 0.015-0.053 µm for aerosol in Aitken mode, 0.058-0.27 µm for accumulation mode, and 0.80-3.65 µm for coarse mode. Dynamic partitioning of H2SO4, HNO3, HCl, and NH3 to each mode, related particle-phase thermodynamics, as well as water content and pH of interstitial aerosols, are computed using the MOSAIC module (Zaveri et al, 2008(Zaveri et al, , 2021Lu et al, 2021). Further details describing the dry and wet deposition, aerosol optical properties, radiative transfer, and aerosol-cloud microphysics are described in Supplementary Information; these processes are all based on the standard CAM6-chem.…”

Section: Model Configurationmentioning

confidence: 99%

“…During ATom, an array of instruments was used to collect and analyze daytime air samples from the remote marine environments, providing measurements of DMS, HPMTF, MSA(aq), and nss-SO4 2-(aq). The Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) probed the atmosphere surrounding the ENA observatory on Graciosa Island during summer 2017 and winter 2018 (Wang et al, 2019a(Wang et al, , 2021. ACE-ENA provides high time-resolution in-situ measurements of MSA and sulfate aerosol in the lower troposphere (Zawadowicz et al, 2021).…”

Section: Comparison With Observationsmentioning

confidence: 99%

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Exploring DMS oxidation and implications for global aerosol radiative forcing

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et al. 2021

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Abstract. Aerosol indirect radiative forcing (IRF), which characterizes how aerosols alter cloud formation and properties, is very sensitive to the preindustrial (PI) aerosol burden. Dimethyl sulfide (DMS), emitted from the ocean, is a dominant natural precursor of non-sea-salt sulfate in the PI and pristine present-day (PD) atmospheres. Here we revisit the atmospheric oxidation chemistry of DMS, particularly under pristine conditions, and its impact on aerosol IRF. Based on previous laboratory studies, we expand the simplified DMS oxidation scheme used in the Community Atmospheric Model version 6 with chemistry (CAM6-chem) to capture the OH-addition pathway as well as the H-abstraction pathway and the associated isomerization branch. These additional oxidation channels of DMS produce several stable intermediate compounds, e.g., methanesulfonic acid (MSA) and hydroperoxymethyl thioformate (HPMTF), delay the formation of sulfate, and hence, alter the spatial distribution of sulfate aerosol and radiative impacts. The expanded scheme improves the agreement between modeled and observed concentrations of DMS, MSA, HPMTF, and sulfate over most marine regions based on the NASA Atmospheric Tomography (ATom), the Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA), and the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) measurements. We find that the global HPMTF burden, as well as the burden of sulfate produced from DMS oxidation are relatively insensitive to the assumed isomerization rate, but the burden of HPMTF is very sensitive to a potential additional cloud loss. We find that global sulfate burden under PI and PD emissions increase to 412 Gg-S (+29 %) and 582 Gg-S (+8.8 %), respectively, compared to the standard simplified DMS oxidation scheme. The resulting annual mean global PD direct radiative effect of DMS-derived sulfate alone is −0.11 W m−2. The enhanced PI sulfate produced via the gas-phase chemistry updates alone dampens the aerosol IRF as anticipated (−2.2 W m−2 in standard versus −1.7 W m−2 with updated gas-phase chemistry). However, high clouds in the tropics and low clouds in the Southern Ocean appear particularly sensitive to the additional aqueous-phase pathways, counteracting this change (−2.3 W m−2). This study confirms the sensitivity of aerosol IRF to the PI aerosol loading, as well as the need to better understand the processes controlling aerosol formation in the PI atmosphere and the cloud response to these changes.

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“…In this paper, we used the PM 1 dataset obtained with a particle-into-liquid sampler (PILS) during the summer 2017 flights of the Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) campaign to characterize the acidity of PM 1 over the eastern North Atlantic. Measurements were carried out in the Azores archipelago in the eastern North Atlantic during the ACE-ENA campaign [45]. Although the ACE-ENA campaign had two intense operating periods (IOP) that occurred during summer 2017 (June to July) and winter 2018 (January to February), the PM 1 dataset obtained during the winter IOP was not used because the mass concentrations of many water-soluble aerosol constituents essential for aerosol acidity predictions were very low (i.e., close to or below the limits of detection of aerosol composition measurements).…”

Section: Introductionmentioning

confidence: 99%

Fine Aerosol Acidity and Water during Summer in the Eastern North Atlantic

et al. 2021

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Aerosol pH governs many important atmospheric processes that occur in the marine boundary layer, including regulating halogen and sulfur chemistries, and nutrient fertilization of surface ocean waters. In this study, we investigated the acidity of PM1 over the eastern North Atlantic during the Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) aircraft campaign. The ISORROPIA-II thermodynamic model was used to predict PM1 pH and water. We first investigated the sensitivities of PM1 pH and water predictions to gas-phase NH3 and HNO3 concentrations. Our sensitivity analysis indicated that even though NH3 and HNO3 were present at very low concentrations in the eastern North Atlantic during the campaign, PM1 pH calculations can still be sensitive to NH3 concentrations. Specifically, NH3 was needed to constrain the pH of populations of PM1 that had low mass concentrations of NH4+ and non-volatile cations (NVCs). We next assumed that gas-phase NH3 and HNO3 concentrations during the campaign were 0.15 and 0.09 µg m−3, respectively, based on previous measurements conducted in the eastern North Atlantic. Using the assumption that PM1 were internally mixed (i.e., bulk PM1), we determined that PM1 pH ranged from 0.3–8.6, with a mean pH of 5.0 ± 2.3. The pH depended on both and . was controlled primarily by the NVCs/SO42− molar ratio, while was controlled by the SO42− mass concentration and RH. Changes in pH with altitude were driven primarily by changes in SO42−. Since aerosols in marine atmospheres are rarely internally mixed, the scenario where non-sea salt species and sea-salt species were present in two separate aerosol modes in the PM1 (i.e., completely externally mixed) was also considered. Smaller pH values were predicted for the aerosol mode comprised only of non-sea salt species compared to the bulk PM1 (difference of around 1 unit on average). This was due to the exclusion of sea-salt species (especially hygroscopic alkaline NVCs) in this aerosol mode, which led to increases in values and decreases in values. This result demonstrated that assumptions of aerosol mixing states can impact aerosol pH predictions substantially, which will have important implications for evaluating the nature and magnitude of pH-dependent atmospheric processes that occur in the marine boundary layer.

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Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA)

Cited by 52 publications

References 124 publications

Vertical profiles of trace gas and aerosol properties over the eastern North Atlantic: variations with season and synoptic condition

Vertical profiles of trace gas and aerosol properties over the eastern North Atlantic: variations with season and synoptic condition

Exploring DMS oxidation and implications for global aerosol radiative forcing

Fine Aerosol Acidity and Water during Summer in the Eastern North Atlantic

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