A large source of cloud condensation nuclei from new particle formation in the tropics

Williamson, Christina; Kupc, Agnieszka; Axisa, Duncan; Bilsback, Kelsey R.; Bui, T. Paul; Campuzano‐Jost, P.; Dollner, Maximilian; Froyd, K. D.; Hodshire, Anna L.; Jimenez, José L.; Kodros, John K.; Luo, Gan; Murphy, D. M.; Nault, Benjamin A.; Ray, E. A.; Weinzierl, Bernadett; Wilson, J. C.; Yu, Fangqun; Yu, Pengfei; Pierce, Jeffrey R.; Brock, C. A.

doi:10.1038/s41586-019-1638-9

Cited by 191 publications

(197 citation statements)

References 58 publications

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“…VOCs (Schulz et al, 2018). In fact, since both gases are known to contribute to SOA formation, the elevated mixing ratios of glyoxal and methylglyoxal in the upper troposphere further lend support to the proposed SOA formation from products of isoprene oxidation as observed by Schulz et al (2018); Andreae et al (2018) and Williamson et al (2019) over the Amazon Basin and generally in the tropics.…”

Section: Resultssupporting

confidence: 54%

Profiling of formaldehyde, glyoxal, methylglyoxal, and CO over the Amazon: Normalised excess mixing ratios and related emission factors in biomass burning plumes

Kluge¹,

Hüneke²,

Knecht³

et al. 2020

Preprint

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Abstract. We report on airborne measurements of tropospheric mixing ratios and vertical profiles of CH2O, C2H2O2, C3H4O2*, and CO over the Amazon Basin during the ACRIDICON-CHUVA campaign from the German High Altitude and Long-range research aircraft (HALO) in fall 2014. The joint observation of in situ CO and remotely measured CH2O, C2H2O2, C3H4O2*, together with visible imagery and air mass back trajectory modelling using NOAA HYSPLIT (National Oceanic Atmospheric Administration, HYbrid Single-Particle Lagrangian Integrated Trajectory) allow us to discriminate between the probing of background tropical air, in which the concentration of the measured species results from the oxidation of biogenically emitted VOCs (mostly isoprene), and measurements of moderately to strongly polluted air masses affected by biomass burning emissions or the city plume of Manaus. For twelve near surface measurements of fresh biomass burning plumes, normalized excess mixing ratios of C2H2O2 and C3H4O2* with respect to CH2O are inferred and compared to recent studies. The mean RGF = 0.07 (range 0.02–0.11) is in good agreement with recent reports which suggest RGF to be significantly lower than previously assumed in global CTM models. The mean RMF = 0.98 (range 0.09–1.50) varies significantly during the different observational settings, but overall appears to be much larger (up to a factor of 5) than previous reports suggest when applaying a correction factor of 2.0 ± 0.5 to account for the additional dicarbonyls included in the C3H4O2* measurements. Using recently reported emission factors of CH2O for tropical forests, our observations suggest emission factors of EFG = 0.25 (range 0.11 to 0.52) g per kg for C2H2O2, and EFM = 4.7 (range 0.5 to 8.64) g per kg for C3H4O2*. While EFG agrees well with recent reports, EFM is (like RMF) slightly larger than reported in other studies, presumably due to the different plume ages or fuels studied. Our observations of these critical carbonyls and intermediate oxidation products may support future photochemical modelling of air pollution over tropical vegetation, as well as validate past and present space-borne observations of the respective species.

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Section: Resultssupporting

confidence: 54%

Profiling of formaldehyde, glyoxal, methylglyoxal, and CO over the Amazon: Normalised excess mixing ratios and related emission factors in biomass burning plumes

Kluge¹,

Hüneke²,

Knecht³

et al. 2020

Preprint

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“…A wide variety of observations indicate that ultrafine aerosol particles can be present in large quantities in the upper troposphere of the Amazon region (Andreae et al, ; Clarke et al, ; Krejci et al, ) as well as in tropical convective regions over both the Pacific and Atlantic Ocean (Williamson et al, ). These particles are believed to form from condensable vapors, which most likely are either directly transported into the upper troposphere by deep convective clouds or formed during convective transport (Clarke, ; Ekman et al, , ; Twohy et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…The Deep Convective Clouds and Chemistry (DC3) field campaign (Barth et al, ) has provided a substantial number of measurements and insights on vertical trace gas transport (Barth et al, ; Bela et al, , ; Fried et al, ; Li et al, ) and wet scavenging of aerosols (Yang et al, ). Aircraft measurements done during the NASA Atmospheric Tomography Mission (ATom) (Wofsy et al, ) has improved our understanding of new particle formation on a global scale over oceanic regions (Williamson et al, ).…”

Section: Introductionmentioning

confidence: 99%

A Novel Framework to Study Trace Gas Transport in Deep Convective Clouds

Bardakov

Riipinen

Krejci

et al. 2020

J Adv Model Earth Syst

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Deep convective clouds reach the upper troposphere (8-15 km height). In addition to moisture and aerosol particles, they can bring aerosol precursor gases and other reactive trace gases from the planetary boundary layer to the cloud top. In this paper, we present a method to estimate trace gas transport based on the analysis of individual air parcel trajectories. Large eddy simulation of an idealized deep convective cloud was used to provide realistic environmental input to a parcel model. For a buoyant parcel, we found that the trace gas transport approximately follows one out of three scenarios, determined by a combination of the equilibrium vapor pressure (containing information about water-solubility and pure component saturation vapor pressure) and the enthalpy of vaporization. In one extreme, the trace gas will eventually be completely removed by precipitation. In the other extreme, there is almost no vapor condensation on hydrometeors and most of the gas is transported to the top of the cloud. The scenario in between these two extremes is also characterized by strong gas condensation, but a small fraction of the trace gas may still be transported aloft. This approach confirms previously suggested patterns of inert trace gas behavior in deep convective clouds, agrees with observational data, and allows estimating transport in analytically simple and computationally efficient way compared to explicit cloud-resolving model calculations.Plain Language Summary Gas transport by deep convective clouds can impact many atmospheric processes including new particle formation, which increases the amount of aerosols in the upper troposphere (8-15 km altitude). In this paper, we suggest a method for calculating the amount of trace gas that can survive transport inside a deep convective cloud. The model is applied to an idealized cloud event, and the results show that among other parameters, transport strongly depends on the physical properties of the gas. The model framework allows us to identify boundaries of the main gas properties defining two extreme scenarios for the gas: full removal by precipitation or complete transport of the gas aloft.

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“…This nss-SO 4 production depends significantly on precursor concentrations and favourable meteorological conditions (Bianchi et al, 2016), while the resulting size distribution of nss-SO 4 aerosol is affected by the surface area concentration of other aerosols that can act as condensation sinks (O'Dowd and de Leeuw, 2007). In both the tropics and the Southern Ocean, cloud-based convective transport of air masses into the free troposphere has been shown to result in new particle formation (NPF) (Clarke et al, 1998;Williamson et al, 2019). The colder air temperatures of the free troposphere promote partitioning into the aerosol phase, while the in-cloud wet scavenging of CCN removes competing condensation sinks.…”

Section: Introductionmentioning

confidence: 99%

Marine productivity and synoptic meteorology drive summer-time variability in Southern Ocean aerosols

Alroe¹,

Cravigan²,

Miljevic³

et al. 2019

Preprint

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Abstract. Cloud-radiation interactions over the Southern Ocean are not well constrained in climate models, in part due to uncertainties in the sources, concentrations and cloud-forming potential of aerosol in this region. To date, most studies in this region have reported measurements from fixed terrestrial stations or a limited set of instrumentation, and often present findings as broad seasonal or latitudinal trends. Here, we present an extensive set of aerosol and meteorological observations obtained during an austral summer cruise across the full width of the Southern Ocean south of Australia. Three episodes of continental-influenced air masses were identified, including an apparent transition between the Ferrel atmospheric cell and the polar cell at approximately 64° S. During the other two episodes, synoptic-scale weather patterns diverted air masses across distances greater than 1000 km from the Australian and Antarctic coastlines, respectively, indicating that a large proportion of the Southern Ocean may be periodically influenced by continental air masses. In all three cases, a highly cloud-active accumulation mode dominated the size distribution, with up to 93 % of the total number concentration activating as cloud condensation nuclei. In contrast, sampling periods influenced by marine air masses frequently demonstrated a correlation between air mass trajectories over regions of high biological productivity and subsequent enhancement of an Aitken mode centred at approximately 30 nm and contributing an average of 71 % of the total aerosol number concentration. Although these small diameters limited their contribution to cloud condensation nuclei concentrations, Aitken number concentrations and diameters were highly variable. A detailed investigation of the marine air masses revealed that this variability may be attributed to the availability of biogenic precursors, the competing influence of condensation sinks (such as sea spray aerosol) and vertical transport between the marine boundary layer and the free troposphere. This variability of the marine Aitken mode as well as the instances of long-range transport were governed by synoptic-scale weather systems, through their influence on air mass trajectories and both generation and depletion of condensation sinks. These results demonstrate the highly dynamic nature of Southern Ocean aerosol and their complex dependence on both biological productivity and synoptic-scale weather systems.

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A large source of cloud condensation nuclei from new particle formation in the tropics

Cited by 191 publications

References 58 publications

Profiling of formaldehyde, glyoxal, methylglyoxal, and CO over the Amazon: Normalised excess mixing ratios and related emission factors in biomass burning plumes

Profiling of formaldehyde, glyoxal, methylglyoxal, and CO over the Amazon: Normalised excess mixing ratios and related emission factors in biomass burning plumes

A Novel Framework to Study Trace Gas Transport in Deep Convective Clouds

Marine productivity and synoptic meteorology drive summer-time variability in Southern Ocean aerosols

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