New Directions: The impact of oceanic iron fertilisation on cloud condensation nuclei

2008 ◽  
Vol 42 (22) ◽  
pp. 5728-5730 ◽  
Author(s):  
Matthew T. Woodhouse ◽  
Graham W. Mann ◽  
Kenneth S. Carslaw ◽  
Olivier Boucher
Keyword(s):  
Cloud Condensation Nuclei ◽  
Condensation Nuclei ◽  
New Directions ◽  
The Impact

scholarly journals Measured and modelled Cloud Condensation Nuclei (CCN) concentration in São Paulo, Brazil: the importance of aerosol size-resolved chemical composition on CCN concentration prediction

2013 ◽  
Vol 13 (12) ◽  
pp. 32353-32389 ◽  
Author(s):  
G. P. Almeida ◽  
J. Brito ◽  
C. A. Morales ◽  
M. F. Andrade ◽  
P. Artaxo
Keyword(s):  
Chemical Composition ◽  
Real Time ◽  
Cloud Condensation Nuclei ◽  
Bulk Composition ◽  
Sao Paulo ◽  
Aerosol Size Distribution ◽  
São Paulo ◽  
Condensation Nuclei ◽  
Aerosol Composition ◽  
The Impact

Abstract. Measurements of cloud condensation nuclei (CCN), aerosol size distribution and non-refractory chemical composition were performed from 16 to 31 October 2012 in the São Paulo Metropolitan Area (SPMA), Brazil. CCN measurements were performed at 0.2%, 0.4%, 0.6%, 0.8% and 1.0% water supersaturation and were subsequently compared with Köhler theory, considering the chemical composition. Real-time chemical composition has been obtained deploying for the first time in SPMA an Aerosol Chemical Ionization Monitor (ACSM). CCN closure analyses were performed considering internal mixture. Average aerosol composition during the studied period yielded 4.81 ± 3.05, 3.26 ± 2.10, 0.30 ± 0.27, 0.52 ± 0.32, 0.37 ± 0.21 and 0.04 ± 0.04 μg m−3 for organics, BC, NH4, SO4, NO3 and Cl, respectively. Particle number concentration was 12 813 ± 5350 cm−3, being a large fraction in the nucleation mode. CCN concentrations were on average 1090 ± 328 cm−3 and 3570 ± 1695 cm−3 at SS = 0.2% and SS = 1.0%, respectively. Results show an increase in aerosol hygroscopicity in the afternoon as a result of aerosol photochemical processing, leading to an enhancement of both organic and inorganic secondary aerosols in the atmosphere, as well as an increase in aerosol average diameter. Considering the bulk composition alone, CCN concentrations were substantially overpredicted (29.6 ± 45.1% at 0.2% supersaturation and 57.3 ± 30.0% at 1.0% supersaturation). Overall, the impact of composition on the calculated NCCN decreases with decreasing supersaturation, partially because using bulk composition introduces less bias for large diameters and lower critical supersaturations. Results suggest that the consideration of only inorganic fraction improves the calculated NCCN. Introducing a size-dependent chemical composition based on filter measurements from previous campaigns has considerably improved simulated values for NCCN (average overprediction error 3.0 ± 33.4% at 0.20% supersaturation and average under prediction error 2.4 ± 20.5% at 1.0% supersaturation). This study provides the first insight on aerosol real-time composition and hygroscopicity on a~site strongly impacted by emissions of a unique vehicular fleet due to the extensive biofuel usage.

scholarly journals Sensitivity Studies on the Impact of Dust and Aerosol Pollution Acting as Cloud Nucleating Aerosol on Orographic Precipitation in the Colorado River Basin

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Vandana Jha ◽  
William R. Cotton ◽  
Gustavo G. Carrió ◽  
Robert Walko
Keyword(s):  
River Basin ◽  
Colorado River ◽  
Cloud Condensation Nuclei ◽  
Winter Season ◽  
Colorado River Basin ◽  
Orographic Precipitation ◽  
Condensation Nuclei ◽  
Aerosol Pollution ◽  
Sensitivity Studies ◽  
The Impact

In this study, we examine the cumulative effect of pollution aerosol and dust acting as cloud nucleating aerosol;cloud condensation nuclei (CCN), giant cloud condensation nuclei, and ice nuclei (IN), on orographic precipitation in the Rocky Mountains. We analyze the results of sensitivity studies for specific cases in 2004-2005 winter season to analyze the relative impact of aerosol pollution and dust acting as CCN and IN on precipitation in the Colorado River Basin. Dust is varied from 3 to 10 times in the experiments, and the response is found to be nonmonotonic and depends on various environmental factors. The sensitivity studies show that adding dust in a wet system increases precipitation when IN effects are dominant. For a relatively dry system high concentrations of dust can result in overseeding the clouds and reductions in precipitation. However, when adding dust to a system with warmer cloud bases where drizzle formation is active, the response is nonmonotonic.

Acoustic Cloud Condensation Nuclei Counter

2005 ◽  
Author(s):  
Abhijit Deshpande ◽  
Marcellin Zahui
Keyword(s):  
Water Surface ◽  
Cloud Condensation Nuclei ◽  
Droplet Diameter ◽  
Bubble Formation ◽  
Maximum Velocity ◽  
Acoustic Energy ◽  
Water Droplets ◽  
Condensation Nuclei ◽  
Micro Scale ◽  
The Impact

Analysis and simulation of an acoustic cloud condensation nuclei counter is presented. The instrument is capable of accurately counting the number of micro scale water droplets impacting a water surface. The sound produced underwater by the water droplets is determined when the droplets strike the water surface with an impact velocity equal to either their terminal or maximum velocity. First, the terminal velocities of the droplets are calculated using Stoke’s law and compared to measured velocities from Gunn and Kinzer. Then the maximum velocities that these droplets can sustain without breaking are calculated as a function of droplet diameter. Second, the sound due to droplet impact is estimated. Due to their size and water surface tension, there is no bubble formation at impact when the droplets are falling with terminal velocities. However conditions for regular bubble entrainments are established and limit velocities are calculated. Assuming that the micro water droplets can be accelerated, the maximum velocities for no bubble entrainments are calculated. The results show that the level of the sound produced by individual micro scale droplet falling with terminal velocity is so small that experimental verification is not possible. However, reasonable level of acoustic energy can be obtained by increasing the impact velocities of the droplets or by measuring the sound radiated by a group of impacting droplets. Finally, the droplets counting process is simulated using a water surface of one centimeter squared and a vertical growth chamber.

scholarly journals The relative impact of cloud condensation nuclei and ice nucleating particle concentrations on phase partitioning in Arctic mixed-phase stratocumulus clouds

2018 ◽  
Vol 18 (23) ◽  
pp. 17047-17059 ◽  
Author(s):  
Amy Solomon ◽  
Gijs de Boer ◽  
Jessie M. Creamean ◽  
Allison McComiskey ◽  
Matthew D. Shupe ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixed Phase ◽  
Radiative Properties ◽  
Condensation Nuclei ◽  
Phase Partitioning ◽  
Cloud Dynamics ◽  
Stratocumulus Clouds ◽  
Cloud Ice ◽  
Mixed Phase Clouds ◽  
The Impact

Abstract. This study investigates the interactions between cloud dynamics and aerosols in idealized large-eddy simulations (LES) of Arctic mixed-phase stratocumulus clouds (AMPS) observed at Oliktok Point, Alaska, in April 2015. This case was chosen because it allows the cloud to form in response to radiative cooling starting from a cloud-free state, rather than requiring the cloud ice and liquid to adjust to an initial cloudy state. Sensitivity studies are used to identify whether there are buffering feedbacks that limit the impact of aerosol perturbations. The results of this study indicate that perturbations in ice nucleating particles (INPs) dominate over cloud condensation nuclei (CCN) perturbations; i.e., an equivalent fractional decrease in CCN and INPs results in an increase in the cloud-top longwave cooling rate, even though the droplet effective radius increases and the cloud emissivity decreases. The dominant effect of ice in the simulated mixed-phase cloud is a thinning rather than a glaciation, causing the mixed-phase clouds to radiate as a grey body and the radiative properties of the cloud to be more sensitive to aerosol perturbations. It is demonstrated that allowing prognostic CCN and INPs causes a layering of the aerosols, with increased concentrations of CCN above cloud top and increased concentrations of INPs at the base of the cloud-driven mixed layer. This layering contributes to the maintenance of the cloud liquid, which drives the dynamics of the cloud system.

scholarly journals Measured and modelled cloud condensation nuclei (CCN) concentration in São Paulo, Brazil: the importance of aerosol size-resolved chemical composition on CCN concentration prediction

2014 ◽  
Vol 14 (14) ◽  
pp. 7559-7572 ◽  
Author(s):  
G. P. Almeida ◽  
J. Brito ◽  
C. A. Morales ◽  
M. F. Andrade ◽  
P. Artaxo
Keyword(s):  
Chemical Composition ◽  
Real Time ◽  
Cloud Condensation Nuclei ◽  
Bulk Composition ◽  
Sao Paulo ◽  
Aerosol Size Distribution ◽  
São Paulo ◽  
Condensation Nuclei ◽  
Kohler Theory ◽  
The Impact

Abstract. Measurements of cloud condensation nuclei (CCN), aerosol size distribution and non-refractory chemical composition were performed from 16 to 31 October 2012 in the São Paulo Metropolitan Area (SPMA), Brazil. CCN measurements were performed at 0.23, 0.45, 0.68, 0.90 and 1.13% water supersaturation and were subsequently compared with the Köhler theory, considering the chemical composition. Real-time chemical composition has been obtained by deploying, for the first time in the SPMA, an aerosol chemical ionization monitor (ACSM). CCN closure analyses were performed considering internal mixtures. Average aerosol composition during the studied period yielded (arithmetic mean~± standard deviation) 4.81 ± 3.05, 3.26 ± 2.10, 0.30 ± 0.27, 0.52 ± 0.32, 0.37 ± 0.21 and 0.04 ± 0.04 μg m−3 for organics, BC, NH4, SO4, NO3 and Cl, respectively. Particle number concentration was 12 813 ± 5350 cm−3, with a dominant nucleation mode. CCN concentrations were on average 1090 ± 328 and 3570 ± 1695 cm−3 at SS = 0.23% and SS = 1.13%, respectively. Results show an increase in aerosol hygroscopicity in the afternoon as a result of aerosol photochemical processing, leading to an enhancement of both organic and inorganic secondary aerosols in the atmosphere, as well as an increase in aerosol average diameter. Considering the bulk composition alone, observed CCN concentrations were substantially overpredicted when compared with the Köhler theory (44.1 ± 47.9% at 0.23% supersaturation and 91.4 ± 40.3% at 1.13% supersaturation). Overall, the impact of composition on the calculated CCN concentration (NCCN) decreases with decreasing supersaturation, partially because using bulk composition introduces less bias for large diameters and lower critical supersaturations, defined as the supersaturation at which the cloud droplet activation will take place. Results suggest that the consideration of only inorganic fraction improves the calculated NCCN. Introducing a size-dependent chemical composition based on filter measurements from previous campaigns has considerably improved simulated values for NCCN (average overprediction error 14.8 ± 38.6% at 0.23% supersaturation and 3.6 ± 21.6% at 1.13% supersaturation). This study provides the first insight on aerosol real-time composition and hygroscopicity at a site strongly impacted by emissions of a unique vehicular fleet due to the extensive biofuel usage.

scholarly journals Low sensitivity of cloud condensation nuclei to changes in the sea-air flux of dimethyl-sulphide

2010 ◽  
Vol 10 (2) ◽  
pp. 3717-3754 ◽  
Author(s):  
M. T. Woodhouse ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
S. M. Vallina ◽  
M. Vogt ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Regulation Mechanism ◽  
Condensation Nuclei ◽  
Subsequent Formation ◽  
Mean Values ◽  
Climate Regulation ◽  
Global Warming Scenario ◽  
Low Sensitivity ◽  
The Impact

Abstract. The emission of dimethylsulphide (DMS) gas by phytoplankton and the subsequent formation of aerosol has long been suggested as an important climate regulation mechanism. The key aerosol quantity is the number concentration of cloud condensation nuclei (CCN), but until recently global models did not include the necessary aerosol physics to quantify CCN. Here we use a global aerosol microphysics model to calculate the sensitivity of CCN to changes in DMS emission using multiple present-day and future sea-surface DMS climatologies. Calculated annual fluxes of DMS to the atmosphere for the five model-derived and one observations based present day climatologies are in the range 15.1 to 32.3 Tg a−1 sulphur. The impact of DMS climatology on surface level CCN concentrations was calculated in terms of summer and winter hemispheric mean values of ΔCCN/ΔFluxDMS, which varied between −51 and +147 cm−3/(mg m−2 day−1 sulphur), with a mean of 56 cm−3/(mg m−2 day−1 sulphur). The range is due to CCN production in the atmosphere being strongly dependent on the spatial distribution of the emitted DMS. The DMS flux from a future globally warmed climatology was 0.2 Tg a−1 sulphur higher than present day with a mean CCN response of 95 cm−3/(mg m−2 day−1 sulphur) relative to present day. The largest CCN response was seen in the southern Ocean, contributing to a Southern Hemisphere mean annual increase of less than 0.2%. We show that the changes in DMS flux and CCN concentration between the present day and global warming scenario are similar to interannual differences due to variability in windspeed. In summary, although DMS makes a significant contribution to global marine CCN concentrations, the sensitivity of CCN to potential future changes in DMS flux is very low. This finding, together with the predicted small changes in future seawater DMS concentrations, suggests that the role of DMS in climate regulation is very weak.

scholarly journals Impact of aerosol–radiation interaction on new particle formation

2021 ◽  
Vol 21 (13) ◽  
pp. 9995-10004
Author(s):  
Gang Zhao ◽  
Yishu Zhu ◽  
Zhijun Wu ◽  
Taomou Zong ◽  
Jingchuan Chen ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Mixing Layer ◽  
Particle Formation ◽  
Radiative Transfer Model ◽  
Aerosol Size Distribution ◽  
Transfer Model ◽  
New Particle Formation ◽  
Condensation Nuclei ◽  
The Impact ◽  
Different Altitudes

Abstract. New particle formation (NPF) is thought to contribute half of the global cloud condensation nuclei. A better understanding of the NPF at different altitudes can help assess the impact of NPF on cloud formation and corresponding physical properties. However, NPF is not sufficiently understood in the upper mixing layer because previous studies mainly focused on ground-level measurements. In this study, the developments of aerosol size distribution at different altitudes are characterized based on the field measurement conducted in January 2019 in Beijing, China. We find that the partition of nucleation-mode particles in the upper mixing layer is larger than that at the ground, which implies that the nucleation processing is more likely to happen in the upper mixing layer than that at the ground. Results of the radiative transfer model show that the photolysis rates of the nitrogen dioxide and ozone increase with altitude within the mixing layer, which leads to a higher concentration of sulfuric acid in the upper mixing layer than that at the ground. Therefore, the nucleation processing in the upper mixing layer should be stronger than that at the ground, which is consistent with our measurement results. Our study emphasizes the influence of aerosol–radiation interaction on the NPF. These results have the potential to improve our understanding of the source of cloud condensation nuclei on a global scale due to the impacts of aerosol–radiation interaction.

scholarly journals The impact of the 1783–1784 AD Laki eruption on global aerosol formation processes and cloud condensation nuclei

2010 ◽  
Vol 10 (2) ◽  
pp. 3189-3228
Author(s):  
A. Schmidt ◽  
K. S. Carslaw ◽  
G. W. Mann ◽  
B. M. Wilson ◽  
T. J. Breider ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Northern Hemisphere ◽  
General Circulation ◽  
Cloud Condensation Nuclei ◽  
General Circulation Models ◽  
Aerosol Formation ◽  
Condensation Nuclei ◽  
Upper Troposphere ◽  
Microphysical Processes ◽  
The Impact

Abstract. The 1783–1784 AD Laki flood lava eruption commenced on 8 June 1783 and released 122 Tg of sulphur dioxide gas over the course of 8 months into the upper troposphere and lower stratosphere above Iceland. Previous studies have examined the impact of the Laki eruption on sulphate aerosol and climate using general circulation models. Here, we study the impact on aerosol microphysical processes, including the nucleation of new particles and their growth to cloud condensation nuclei (CCN) using a comprehensive Global Model of Aerosol Processes (GLOMAP). Total particle concentrations in the free troposphere increase by a factor ~16 over large parts of the Northern Hemisphere in the 3 months following the onset of the eruption. Particle concentrations in the boundary layer increase by a factor 2 to 5 in regions as far away as North America, the Middle East and Asia due to long-range transport of nucleated particles. CCN concentrations (at 0.22% supersaturation) increase by a factor 65 in the upper troposphere with maximum changes in 3-month zonal mean concentrations of ~1400 cm−3 at high northern latitudes. 3-month zonal mean CCN concentrations in the boundary layer at the latitude of the eruption increase by up to a factor 26, and averaged over the Northern Hemisphere, the eruption caused a factor 4 increase in CCN concentrations at low-level cloud altitude. The simulations show that the Laki eruption would have completely dominated as a source of CCN in the pre-industrial atmosphere. The model also suggests an impact of the eruption in the Southern Hemisphere, where CCN concentrations are increased by up to a factor 1.4 at 20° S. Our model simulations suggest that the impact of an equivalent wintertime eruption on upper tropospheric CCN concentrations is only about one-third of that of a summertime eruption. The simulations show that the microphysical processes leading to the growth of particles to CCN sizes are fundamentally different after an eruption when compared to the unperturbed atmosphere, underlining the importance of using a fully coupled microphysics model when studying long-lasting, high-latitude eruptions.

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