Using ATom observations and models to understand what precursors drive NPF in the remote free troposphere

Current estimates suggest that globally, about one third of low-level cloud condensation nuclei (CCN) originate from new particle formation (NPF) in the free troposphere. However, the exact mechanisms of how these new particles form and grow to CCN sizes are not yet well quantified. We investigate the formation of new particles and their initial growth in the remote marine atmosphere over the Pacific and Atlantic basins (~80 &#176;N to ~86 &#176;S using (1) gas-phase and size distribution measurements (0.003-4.8 &#181;m) from the airborne-based NASA Atmospheric Tomography global survey (ATom; 2016-2018), (2) back trajectory data, and (3) two aerosol microphysics box models.In the ATom observations, newly formed particles were ubiquitous at high altitudes throughout broad regions of the tropics and subtropics under low condensation sink conditions and were associated with upwelling in convective clouds. This pattern was observed over four seasons and both ocean basins.In this study, we explore processes that govern NPF and growth in the tropical and subtropical free troposphere, discuss similarities and differences in NPF over both ocean basins, use box models to examine which nucleation schemes (e.g. binary, ternary, or charged) best explain the observations, and evaluate whether sulfuric acid precursors alone can explain the NPF and the initial particle growth. Comparing aerosol size distribution measurements with box model simulations shows that none of the NPF schemes commonly used in global models are consistent with observations, regardless of precursor concentrations. Newer schemes that incorporate organic compounds as nucleating or growth agents can plausibly replicate the observed size distributions. We conclude that organic precursor species may be particularly important in NPF in the tropical upper troposphere, even above marine regions.

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Intercomparison of modal and sectional aerosol microphysics representations within the same 3-D global chemical transport model

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-12-623-2012 ◽

2012 ◽

Vol 12 (1) ◽

pp. 623-689 ◽

Cited By ~ 2

Author(s):

G. W. Mann ◽

K. S. Carslaw ◽

D. A. Ridley ◽

D. V. Spracklen ◽

K. J. Pringle ◽

...

Keyword(s):

Size Distribution ◽

Transport Model ◽

Cloud Condensation Nuclei ◽

Particle Growth ◽

Free Troposphere ◽

Chemical Transport Model ◽

Condensation Nuclei ◽

Chemistry Transport Model ◽

Surface Mass ◽

Cloud Processing

Abstract. A global modal aerosol microphysics module (GLOMAP-mode) is evaluated and improved by comparing against a sectional version (GLOMAP-bin) and observations in the same 3-D global offline chemistry transport model. With both schemes, the model captures the main features of the global particle size distribution, with sub-micron aerosol approximately unimodal in continental regions and bi-modal in marine regions. Initial bin-mode comparisons showed that various size distribution parameter settings (mode widths and inter-modal separation sizes) resulted in clear biases compared to the sectional scheme. By adjusting these parameters in the modal scheme, much better agreement is achieved against the bin scheme and observations. Surface mass of sulphate, sea-salt, black carbon (BC) and organic carbon (OC) are, on the annual mean, within 25 % in the two schemes in nearly all regions. On the annual mean, surface level concentrations of condensation nuclei (CN), cloud condensation nuclei (CCN), surface area density and condensation sink also compare within 25 % in most regions. However, marine CCN concentrations between 30° N and 30° S are systematically higher in the modal scheme, by 25–60 %, which we attribute to differences in size-resolved particle growth or cloud-processing. Larger differences also exist in regions or seasons dominated by biomass burning and in free-troposphere and high-latitude regions. Indeed, in the free-troposphere, GLOMAP-mode BC is a factor 2–4 higher than GLOMAP-bin, likely due to differences in size-resolved scavenging. Nevertheless, in most parts of the atmosphere, we conclude that bin-mode differences are much less than model-observation differences, although some processes are missing in these runs which may pose a bigger challenge to modal schemes (e.g. boundary layer nucleation, ultra-fine sea-spray). The findings here underline the need for a spectrum of complexity in global models, with size-resolved aerosol properties predicted by modal schemes needing to be continually benchmarked and improved against freely evolving sectional schemes and observations.

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An investigation of processes controlling the evolution of the boundary layer aerosol size distribution properties at the Swedish background station Aspvreten

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-4-4507-2004 ◽

2004 ◽

Vol 4 (4) ◽

pp. 4507-4543 ◽

Cited By ~ 2

Author(s):

P. Tunved ◽

J. Ström ◽

H.-C. Hansson

Keyword(s):

Size Distribution ◽

Wet Deposition ◽

Source Area ◽

Aerosol Size Distribution ◽

Back Trajectory ◽

Main Process ◽

Size Distributions ◽

Back Trajectory Analysis ◽

The One ◽

Precipitating Clouds

Abstract. Aerosol size distributions have been measured at the Swedish background station Aspvreten (58.8° N, 17.4° E). Different states of the aerosol were determined using a novel application of cluster analysis. The analysis resulted in eight different clusters capturing the different stages of the aerosol lifecycle. The aerosol was interpreted as belonging to fresh, intermediate and aged type of size distribution and different magnitudes thereof. With aid of back trajectory analysis we present statistics concerning the relation of source area and different meteorological parameters using a non-lagrangian approach. Source area is argued to be important although not sufficient to describe the observed aerosol properties. Especially processing by clouds and precipitation is shown to be crucial for the evolution of the aerosol size distribution. As much as 60% of the observed size distributions present features likely related to cloud processes or wet deposition. The lifetime properties of different sized aerosols are discussed by means of measured variability. Processing by non-precipitating clouds most obviously affect aerosols in the size range 100 nm and larger. This indicates an approximate limit for activation in clouds to 100 nm in this type of environment. The aerosol lifecycle is discussed. Size distributions bearing signs of recent new particle formation (~30% of the observed size distributions) represent the first stage in the lifecycle. Aging may proceed in two directions: either growth by condensation and coagulation or processing by non-precipitating clouds. In both cases mass is accumulated. Wet removal is the main process capable of removing aerosol mass. Wet deposition is argued to be an important mechanism in reaching a state where nucleation may occur (i.e. sufficiently low aerosol surface area) in environments similar to the one studied.

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Quantifying the aerosol effect on droplet size distribution at cloud top

Atmospheric Chemistry and Physics ◽

10.5194/acp-19-7839-2019 ◽

2019 ◽

Vol 19 (11) ◽

pp. 7839-7857

Author(s):

Lianet Hernández Pardo ◽

Luiz Augusto Toledo Machado ◽

Micael Amore Cecchini ◽

Madeleine Sánchez Gácita

Keyword(s):

Size Distribution ◽

Droplet Size ◽

Initial Conditions ◽

Cloud Condensation Nuclei ◽

Droplet Size Distribution ◽

Number Concentration ◽

Population Characteristics ◽

Aerosol Size Distribution ◽

Effective Diameter ◽

Distribution Sensitivity

Abstract. This work uses the number concentration-effective diameter phase-space to test cloud sensitivity to variations in the aerosol population characteristics, such as the aerosol size distribution, number concentration and hygroscopicity. It is based on the information from the top of a cloud simulated by a bin-microphysics single-column model, for initial conditions typical of the Amazon, using different assumptions regarding the entrainment and the aerosol size distribution. It is shown that the cloud-top evolution can be very sensitive to aerosol properties, but the relative importance of each parameter is variable. The sensitivity to each aerosol characteristic varies as a function of the parameter tested and is conditioned by the base values of the other parameters, showing a specific dependence for each configuration of the model. When both the entrainment and the bin treatment of the aerosol are allowed, the largest influence on the droplet size distribution sensitivity was obtained for the median radius of the aerosols and not for the total number concentration of aerosols. Our results reinforce that the cloud condensation nuclei activity can not be predicted solely on the basis of the w∕Na supersaturation-based regimes.

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Fast time response measurements of particle size distributions in the 3–60 nm size range with the nucleation mode aerosol size spectrometer

Atmospheric Measurement Techniques ◽

10.5194/amt-11-3491-2018 ◽

2018 ◽

Vol 11 (6) ◽

pp. 3491-3509 ◽

Cited By ~ 9

Author(s):

Christina Williamson ◽

Agnieszka Kupc ◽

James Wilson ◽

David W. Gesler ◽

J. Michael Reeves ◽

...

Keyword(s):

Particle Size ◽

Size Distribution ◽

Cloud Condensation Nuclei ◽

Radiation Budget ◽

Fast Time ◽

Size Distributions ◽

Free Troposphere ◽

Particle Size Distributions ◽

Nucleation Mode ◽

Data Inversion

Abstract. Earth's radiation budget is affected by new particle formation (NPF) and the growth of these nanometre-scale particles to larger sizes where they can directly scatter light or act as cloud condensation nuclei (CCN). Large uncertainties remain in the magnitude and spatiotemporal distribution of nucleation (less than 10 nm diameter) and Aitken (10–60 nm diameter) mode particles. Acquiring size-distribution measurements of these particles over large regions of the free troposphere is most easily accomplished with research aircraft. We report on the design and performance of an airborne instrument, the nucleation mode aerosol size spectrometer (NMASS), which provides size-selected aerosol concentration measurements that can be differenced to identify aerosol properties and processes or inverted to obtain a full size distribution between 3 and 60 nm. By maintaining constant downstream pressure the instrument operates reliably over a large range of ambient pressures and during rapid changes in altitude, making it ideal for aircraft measurements from the boundary layer to the stratosphere. We describe the modifications, operating principles, extensive calibrations, and laboratory and in-flight performance of two NMASS instruments operated in parallel as a 10-channel battery of condensation particle counters (CPCs) in the NASA Atmospheric Tomography Mission (ATom) to investigate NPF and growth to cloud-active sizes in the remote free troposphere. An inversion technique to obtain size distributions from the discrete concentrations of each NMASS channel is described and evaluated. Concentrations measured by the two NMASS instruments flying in parallel are self-consistent and also consistent with measurements made with an optical particle counter. Extensive laboratory calibrations with a range of particle sizes and compositions show repeatability of the response function of the instrument to within 5–8 % and no sensitivity in sizing performance to particle composition. Particle number, surface area, and volume concentrations from the data inversion are determined to better than 20 % for typical particle size distributions. The excellent performance of the NMASS systems provides a strong analytical foundation to explore NPF around the globe in the ATom dataset.

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Dust plume formation in the free troposphere and aerosol size distribution during the Saharan Mineral Dust Experiment in North Africa

Tellus B ◽

10.3402/tellusb.v67.27170 ◽

2015 ◽

Vol 67 (1) ◽

pp. 27170 ◽

Cited By ~ 13

Author(s):

Basit Khan ◽

Georgiy Stenchikov ◽

Bernadett Weinzierl ◽

Stoitchko Kalenderski ◽

Sergey Osipov

Keyword(s):

Size Distribution ◽

North Africa ◽

Mineral Dust ◽

Aerosol Size Distribution ◽

Free Troposphere

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The background aerosol size distribution in the free troposphere: An analysis of the annual cycle at a high-alpine site

Journal of Geophysical Research Atmospheres ◽

10.1029/1998jd200029 ◽

1998 ◽

Vol 103 (D24) ◽

pp. 31749-31761 ◽

Cited By ~ 55

Author(s):

S. Nyeki ◽

F. Li ◽

E. Weingartner ◽

N. Streit ◽

I. Colbeck ◽

...

Keyword(s):

Size Distribution ◽

Annual Cycle ◽

Aerosol Size Distribution ◽

Free Troposphere

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Cloud condensation nuclei measurements in the marine boundary layer of the Eastern Mediterranean: CCN closure and droplet growth kinetics

Atmospheric Chemistry and Physics ◽

10.5194/acp-9-7053-2009 ◽

2009 ◽

Vol 9 (18) ◽

pp. 7053-7066 ◽

Cited By ~ 129

Author(s):

A. Bougiatioti ◽

C. Fountoukis ◽

N. Kalivitis ◽

S. N. Pandis ◽

A. Nenes ◽

...

Keyword(s):

Size Distribution ◽

Growth Kinetics ◽

Eastern Mediterranean ◽

Cloud Condensation Nuclei ◽

Bulk Composition ◽

Organic Content ◽

Water Soluble ◽

Aerosol Size Distribution ◽

Droplet Growth ◽

Condensation Nuclei

Abstract. Measurements of cloud condensation nuclei (CCN) concentrations (cm−3) between 0.2 and 1.0% supersaturation, aerosol size distribution and chemical composition were performed at a remote marine site in the eastern Mediterranean, from September to October 2007 during the FAME07 campaign. Most of the particles activate at ~0.6% supersaturation, characteristic of the aged nature of the aerosol sampled. Application of Köhler theory, using measurements of bulk composition, size distribution, and assuming that organics are insoluble resulted in agreement between predicted and measured CCN concentrations within 7±11% for all supersaturations, with a tendency for CCN underprediction (16±6%; r2=0.88) at the lowest supersaturations (0.21%). Including the effects of the water-soluble organic fraction (which represent around 70% of the total organic content) reduces the average underprediction bias at the low supersaturations, resulting in a total closure error of 0.6±6%. Using threshold droplet growth analysis, the growth kinetics of ambient CCN is consistent with NaCl calibration experiments; hence the presence of aged organics does not suppress the rate of water uptake in this environment. The knowledge of the soluble salt fraction is sufficient for the description of the CCN activity in this area.

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Regional modelling of aerosol interaction with deep convection and the effect on new particle formation over Amazonia

10.5194/egusphere-egu2020-6244 ◽

2020 ◽

Author(s):

Xuemei Wang ◽

Daniel Grosvenor ◽

Hamish Gordon ◽

Meinrat O. Andreae ◽

Ken Carslaw

Keyword(s):

Boundary Layer ◽

Cloud Condensation Nuclei ◽

Deep Convection ◽

Particle Formation ◽

Nucleation Mechanism ◽

Transport Processes ◽

Radiative Properties ◽

Free Troposphere ◽

New Particle Formation ◽

New Particles

It has been estimated that over 50% of the present-day global low-level cloud condensation nuclei (CCN) are formed from new particle formation (NPF), and that this process has a substantial effect on the radiative properties of shallow clouds (Gordon et al. 2017). In contrast, we have a very limited understanding of how NPF affects deep convective clouds. Deep clouds could interact strongly with NPF because they extend into the high free troposphere where most new particles are formed, and they are responsible for most of the vertical transport of the nucleating vapours. Andreae et al. (2018) hypothesised from ACRIDICON-CHUVA campaign that organic gas molecules are transported by deep convection to the upper troposphere where they are oxidised and produce new particles, which are then be entrained into the boundary layer and grow to CCN-relevent sizes.Here we study the interaction of deep convection and NPF using the United Kingdom Chemistry and Aerosols (UKCA) model coupled with the Cloud-AeroSol Interacting Microphyics (CASIM) embedded in the regional configuration of UK Met Office Hadley Centre Global Environment Model (HadGEM3). We simulate several days over a 1000 km region of the Amazon at 4 km resolution. We then compare the regional model, which resolves cloud up- and downdrafts, with the global model with parameterised convection and low resolution.Our simulations highlight three findings. Firstly, solely using a binary H2SO4-H2O nucleation mechanism strongly underestimates total aerosol concentrations compared to observations by a factor of 1.5-8 below 3 km over the Amazon. This points to the potential role of an additional nucleation mechanism, most likely involving biogenic compounds that occurs throughout more of the free troposphere. Secondly, deep convection transports insoluble gases such as DMS and monoterpenes vertically but not SO2&#160;or H2SO4. The time scale for DMS oxidation (~ 1 day) is much longer than for monoterpene (1-2 hours), which points to the importance of simulating biogenic nucleation over the Amazon in a cloud-resolving model, while lower-resolution global models may adequately capture DMS effects on H2SO4 nucleation. Finally, we also examine the Andreae et al (2018) hypothesis of aerosol supply to the boundary layer by quantifying cloud-free and cloudy up- and downdraft transport. The transport of newly formed aerosols into the boundary layer is 8 times greater in cloud-free regions than in the clouds, but these transport processes are of similar magnitude for large aerosols.

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On aerosol hygroscopicity, cloud condensation nuclei (CCN) spectra and critical supersaturation measured at two remote islands of Korea between 2006 and 2009

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-11-19683-2011 ◽

2011 ◽

Vol 11 (7) ◽

pp. 19683-19727 ◽

Cited By ~ 2

Author(s):

J. H. Kim ◽

S. S. Yum ◽

S. Shim ◽

S.-C. Yoon ◽

J. G. Hudson ◽

...

Keyword(s):

Size Distribution ◽

Total Concentration ◽

Cloud Condensation Nuclei ◽

Geometric Mean ◽

Aerosol Size Distribution ◽

Monitoring Site ◽

Hygroscopic Growth ◽

Condensation Nuclei ◽

Critical Supersaturation ◽

Aerosol Hygroscopicity

Abstract. Aerosol size distribution, total concentration (i.e., condensation nuclei (CN) concentration, NCN), cloud condensation nuclei (CCN) concentration (NCCN), hygroscopicity at ~90 % relative humidity (RH) were measured at a background monitoring site at Gosan, Jeju Island, south of the Korea Peninsula in August 2006, April to May 2007 and August to October 2008. Similar measurement took place in August 2009 at another background site (Baengnyeongdo Comprehensive Monitoring Observatory, BCMO) on the island of Baengnyeongdo, off the west coast of the Korean Peninsula. Both islands were found to be influenced by continental sources regardless of season and year. Average values for all of the measured NCCN at 0.2, 0.6 and 1.0 % supersaturations (S), NCN, and geometric mean diameter (Dg) from both islands were in the range of 1043–3051 cm−3, 2076–4360 cm−3, 2713–4694 cm−3, 3890–5117 cm−3 and 81–98 nm, respectively. Although the differences in Dg and NCN were small between Gosan and BCMO, NCCN at various S was much higher at the latter, which is closer to China. Most of the aerosols were internally mixed and no notable differences in hygroscopicity were found between the days of strong pollution influence and the non-pollution days for both islands. During the 2008 and 2009 campaigns, critical supersaturation for cloud nucleation (Sc) for selected particle sizes was measured. Particles of 100 nm diameters had mean Sc of 0.19 ± 0.02 % during 2008 and those of 81 and 110 nm diameters had mean Sc of 0.26 ± 0.07 % and 0.17 ± 0.04 %, respectively, during 2009. Hygroscopicity parameters estimated from the measured Sc were mostly higher than the ones from the measured hygroscopic growth at ~90 % RH. For the 2008 campaign, NCCN at 0.2, 0.6 and 1.0 % S were predicted based on the measured dry particle size distribution and various ways of representing aerosol hygroscopicity. The best closure was obtained when temporally varying and size-resolved hygroscopicity information from HTDMA was used, for which the average relative deviations from the measured values were 19 % for 1.0 % S and 28 % for 0.2 % S. Prescribing a constant hygroscopicity parameter suggested in literature (κ = 0.3) for all sizes and time resulted in the average relative deviations, 25–40 %. When constant hygroscopicity was assumed, the relative deviation tended to increase with decreasing NCCN, which was accompanied by increase of sub-100 nm fraction. These results suggest that hygroscopicity information for aerosols of diameters smaller than 100 nm is crucial for more accurate prediction of NCCN.

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Impact of aerosol composition on cloud condensation nuclei activity

Atmospheric Chemistry and Physics ◽

10.5194/acp-12-3783-2012 ◽

2012 ◽

Vol 12 (8) ◽

pp. 3783-3790 ◽

Cited By ~ 28

Author(s):

Q. Zhang ◽

J. Meng ◽

J. Quan ◽

Y. Gao ◽

D. Zhao ◽

...

Keyword(s):

Size Distribution ◽

Field Experiments ◽

Cloud Condensation Nuclei ◽

Diffusion Chamber ◽

Aerosol Size Distribution ◽

Condensation Nuclei ◽

Aerosol Composition ◽

Rate Of Increase ◽

The Impact ◽

Ccn Activity

Abstract. The impact of aerosol composition on cloud condensation nuclei (CCN) activity were analyzed in this study based on field experiments carried out at downtown Tianjin, China in September 2010. In the experiments, the CCN measurements were performed at supersaturation (SS) of 0.1%, 0.2% and 0.4% using a thermal-gradient diffusion chamber (DMT CCNC), whereas the aerosol size distribution and composition were simultaneously measured with a TSI SMPS and an Aerodyne Aerosol Mass Spectrometer (AMS), respectively. The results show that the influence of aerosol composition on CCN activity is notable under low SS (0.1%), and their influence decreased with increasing SS. For example, under SS of 0.1%, the CCN activity increases from 4.5±2.6% to 12.8±6.1% when organics fraction decrease from 30–40% to 10–20%. The rate of increase reached up to 184%. While under SS of 0.4%, the CCN activity increases only from 35.7±19.0% to 46.5±12.3% correspondingly. The calculated NCCN based on the size-resolved activation ratio and aerosol number size distribution correlated well with observed NCCN at high SS (0.4%), but this consistence decreased with the falling of SS. The slopes of linear fitted lines between calculated and observed NCCN are 0.708, 0.947, and 0.995 at SS of 0.1%, 0.2% and 0.4% respectively. Moreover, the stand deviation (SD) of calculated NCCN increased with the decreasing of SS. A case study of CCN closure analyses indicated that the calculated error of NCCN could reach up to 34% at SS of 0.1% if aerosol composition were not included, and the calculated error decreased with the raising of SS. It is decreased to 9% at SS of 0.2%, and further decreased to 4% at SS of 0.4%.

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