scholarly journals Annual cycle of Antarctic baseline aerosol: controlled by photooxidation-limited aerosol formation

2014 ◽  
Vol 14 (6) ◽  
pp. 3083-3093 ◽  
Author(s):  
M. Fiebig ◽  
D. Hirdman ◽  
C. R. Lunder ◽  
J. A. Ogren ◽  
S. Solberg ◽  
...  
Keyword(s):  
Annual Cycle ◽  
Particle Number ◽  
Climate Models ◽  
Aerosol Formation ◽  
Particle Volume ◽  
Transport Pathway ◽  
Air Masses ◽  
Total Particle ◽  
The Antarctic ◽  
Aerosol Properties

Abstract. This article investigates the annual cycle observed in the Antarctic baseline aerosol scattering coefficient, total particle number concentration, and particle number size distribution (PNSD), as measured at Troll Atmospheric Observatory. Mie theory shows that the annual cycles in microphysical and optical aerosol properties have a common cause. By comparison with observations at other Antarctic stations, it is shown that the annual cycle is not a local phenomenon, but common to central Antarctic baseline air masses. Observations of ground-level ozone at Troll as well as backward plume calculations for the air masses arriving at Troll demonstrate that the baseline air masses originate from the free troposphere and lower stratosphere region, and descend over the central Antarctic continent. The Antarctic summer PNSD is dominated by particles with diameters <100 nm recently formed from the gas-phase despite the absence of external sources of condensible gases. The total particle volume in Antarctic baseline aerosol is linearly correlated with the integral insolation the aerosol received on its transport pathway, and the photooxidative production of particle volume is mostly limited by photooxidative capacity, not availability of aerosol precursor gases. The photooxidative particle volume formation rate in central Antarctic baseline air is quantified to 207 ± 4 μm3/(MJ m). Further research is proposed to investigate the applicability of this number to other atmospheric reservoirs, and to use the observed annual cycle in Antarctic baseline aerosol properties as a benchmark for the representation of natural atmospheric aerosol processes in climate models.

scholarly journals Annual cycle of Antarctic baseline aerosol: controlled by photooxidation-limited aerosol formation

2013 ◽  
Vol 13 (9) ◽  
pp. 23057-23088
Author(s):  
M. Fiebig ◽  
D. Hirdman ◽  
C. R. Lunder ◽  
J. A. Ogren ◽  
S. Solberg ◽  
...  
Keyword(s):  
Annual Cycle ◽  
Particle Number ◽  
Climate Models ◽  
Aerosol Formation ◽  
Particle Volume ◽  
Transport Pathway ◽  
Air Masses ◽  
Total Particle ◽  
The Antarctic ◽  
Aerosol Properties

Abstract. This article investigates the annual cycle observed in the Antarctic baseline aerosol scattering coefficient, total particle number concentration, and particle number size distribution (PNSD) as measured at Troll Atmospheric Observatory. Mie-theory shows that the annual cycles in microphysical and optical aerosol properties have a common cause. By comparison with observations at other Antarctic stations, it is shown that the annual cycle is not a local phenomenon, but common to Central Antarctic baseline air masses. Observations of ground-level ozone at Troll as well as backward plume calculations for the air masses arriving at Troll demonstrate that the baseline air masses originate from the free troposphere and lower stratosphere region, and descend over the Central Antarctic continent. The Antarctic summer PNSD is dominated by particles with diameters < 100 nm recently formed from the gas-phase despite the absence of external sources of condensible gases. The total particle volume in Antarctic baseline aerosol is linearly correlated with the integral insolation the aerosol received on its transport pathway, and the photooxidative production of particle volume is mostly limited by photooxidative capacity, not availability of aerosol precursor gases. The photooxidative particle volume formation rate in Central Antarctic baseline air is quantified to 207 ± 4 μm3/(MJ m). Further research is proposed to investigate the applicability of this number to other atmospheric reservoirs, and to use the observed annual cycle in Antarctic baseline aerosol properties as a benchmark for the representation of natural atmospheric aerosol processes in climate models.

scholarly journals Vertical marine snow distribution in the stratified, hypersaline, and anoxic Orca Basin (Gulf of Mexico)

Elem Sci Anth ◽  
2019 ◽  
Vol 7 ◽  
Author(s):  
Arne Diercks ◽  
Kai Ziervogel ◽  
Ryan Sibert ◽  
Samantha B. Joye ◽  
Vernon Asper ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Gulf Of Mexico ◽  
Particle Number ◽  
Sea Surface ◽  
Marine Snow ◽  
Particle Volume ◽  
Total Particle Number ◽  
Total Particle ◽  
Snow Distribution ◽  
Orca Basin

We present a complete description of the depth distribution of marine snow in Orca Basin (Gulf of Mexico), from sea surface through the pycnocline to within 10 m of the seafloor. Orca Basin is an intriguing location for studying marine snow because of its unique geological and hydrographic setting: the deepest ~200 m of the basin are filled with anoxic hypersaline brine. A typical deep ocean profile of marine snow distribution was observed from the sea surface to the pycnocline, namely a surface maximum in total particle number and midwater minimum. However, instead of a nepheloid (particle-rich) layer positioned near the seabed, the nepheloid layer in the Orca Basin was positioned atop the brine. Within the brine, the total particle volume increased by a factor of 2–3 while the total particle number decreased, indicating accumulation and aggregation of material in the brine. From these observations we infer increased residence time and retention of material within the brine, which agrees well with laboratory results showing a 2.2–3.5-fold reduction in settling speed of laboratory-generated marine snow below the seawater-brine interface. Similarly, dissolved organic carbon concentration in the brine correlated positively with measured colored dissolved organic matter (r2 = 0.92, n = 15), with both variables following total particle volume inversely through the pycnocline. These data indicate the release of dissolved organic carbon concomitant with loss in total particle volume and increase in particle numbers at the brine-seawater interface, highlighting the importance of the Orca Basin as a carbon sink.

scholarly journals Aerosol ageing in an urban plume – implication for climate

2011 ◽  
Vol 11 (12) ◽  
pp. 5897-5915 ◽  
Author(s):  
P. Roldin ◽  
E. Swietlicki ◽  
A. Massling ◽  
A. Kristensson ◽  
J. Löndahl ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Particle Number ◽  
Particulate Emissions ◽  
Aerosol Formation ◽  
Aerosol Dynamics ◽  
Cloud Properties ◽  
Total Particle ◽  
Physical Particle ◽  
Urban Plume ◽  
Phase Chemistry

Abstract. The climate effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmö city in southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind of Malmö, through the urban background environment and finally tens and hundreds of kilometers downwind of Malmö. The model results were evaluated using measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (~ 3 h) downwind, in the center of the Malmö plume, is about 3700 cm−3 of which the Malmö contribution is roughly 30%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmö increases the secondary aerosol formation with a maximum of 0.7–0.8 μg m−3 6 to 18 h downwind of Malmö. The secondary mass contribution dominates over the primary soot contribution from Malmö already 3 to 4 h downwind of the emission sources and contributes to an enhanced total surface direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from −0.3 to −3.3 W m−2 depending on the distance from Malmö, and the specific cloud properties.

scholarly journals Aerosol ageing in an urban plume – implications for climate and health

2010 ◽  
Vol 10 (8) ◽  
pp. 18731-18780 ◽  
Author(s):  
P. Roldin ◽  
E. Swietlicki ◽  
A. Massling ◽  
A. Kristensson ◽  
J. Löndahl ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
Particle Number ◽  
Particulate Emissions ◽  
Aerosol Formation ◽  
Aerosol Dynamics ◽  
Cloud Properties ◽  
Total Particle ◽  
Physical Particle ◽  
Climate And Health ◽  
Urban Plume

Abstract. The climate and health effects downwind of an urban area resulting from gaseous and particulate emissions within the city are as yet inadequately quantified. The aim of this work was to estimate these effects for Malmö city in Southern Sweden (population 280 000). The chemical and physical particle properties were simulated with a model for Aerosol Dynamics, gas phase CHEMistry and radiative transfer calculations (ADCHEM) following the trajectory movement from upwind Malmö, through the urban background environment and finally tens and hundreds of kilometers downwind Malmö. The model results were validated with measurements of the particle number size distribution and chemical composition. The total particle number concentration 50 km (~3 h) downwind in the center of the Malmö plume is about 3800 cm−3 and the Malmö contribution is roughly 35%. Condensation of nitric acid, ammonium and to a smaller extent oxidized organic compounds formed from the emissions in Malmö increases the secondary aerosol formation with a maximum of 0.6–0.7 μg/m3 6 to 18 h downwind of Malmö. The secondary mass contribution dominates over the primary soot contribution from Malmö already 2 to 3 h after the emissions and gives an enhanced total top of the atmosphere direct or indirect aerosol shortwave radiative forcing in the center of the urban plume ranging from −0.3 to −2.3 W m−2 depending on the distance from Malmö, and the cloud properties. It also gives an increased respiratory tract deposited mass dose, which increases with the distance downwind Malmö.

scholarly journals Using Computational Fluid Dynamics to Evaluate the Role of Air Purification in Reducing Fallow Time in Dentistry 

2020 ◽  
Author(s):  
Neha Raghava ◽  
Bojan Vidovic
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Particle Number ◽  
Air Purification ◽  
Particle Volume ◽  
Dental Surgery ◽  
Infection Transmission ◽  
Air Purifier ◽  
Total Particle ◽  
Open Window

Abstract AbstractIn dentistry, fallow time is a period which allows for airborne pathogens to settle out of the air and mitigate the risk of airborne infection transmission to dental professionals and staff. The current recommendation is a one hour period.Aims and Objectives We aim to show that air purification devices are an undervalued adjunctive measure to mitigate the risk of airborne transmission of pathogens, and so reduce fallow time.Methods Using a computational fluid dynamics software, we created a virtual dental surgery, and simulated a ten-minute aerosol generating procedure. We then modelled air flow in the room with no ventilation, and then the same room with an air purifier at a throughput of 430m3 h-1, and subsequently the room with one open window providing 6 ACH and no purifier. The particles released were monitored and their behaviour and airborne time measured and collated.Results and conclusions The room with no ventilation had a total particle number at 600s of 4.5million, which required 8400s to reduce by 99%. With an open window providing 6 ACH, we obtained a value of 2500s for a 99% reduction in airborne particles, and a similar peak particle volume. Conversely, when using an air purifier throughout the procedure, the peak particle number was ten times lower than the peak number without ventilation, or with an open window, and after the particle injection 99% airborne particle reduction was achieved 60s. Our findings suggest that the use of an air purifier greatly reduces the total particle volume in the air during the aerosol generating procedure, and the fallow period needed. The values found with 6 ACH and an open window are corroborated in other literature. The use of air purification could greatly reduce the risk of infection transmission in a dental surgery.

scholarly journals Characterisation of the Antarctic stratospheric vortex mixing barrier

2021 ◽  
Author(s):  
◽  
Christopher Cameron
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Effective Diffusivity ◽  
Global Climate Models ◽  
Model Representation ◽  
Climate Modelling ◽  
Air Masses ◽  
The Face ◽  
The Antarctic

<p>The strongest stratospheric circulation in the Southern Hemisphere is the Antarctic Circumpolar Vortex (ACV) which forms each winter and spring as a zone of westerly winds surrounding Antarctica, presenting a barrier to transport of air masses between middle and high-latitudes. This barrier contributes to stratospheric temperatures above the polar region dropping sufficiently low in spring to allow for the processes leading to ozone destruction. Unfortunately, the ACV is generally not well simulated in Global Climate Models (GCMs), and this presents a challenge for model accuracy and projections in the face of a changing climate and a recovering ozone hole.  In this research, an assessment is made of the performance of a range of mixing metrics in representing the ACV based on reanalyses, including: Effective Diffusivity, Contour Crossing, the Lagrangian function $M$, and Meridional Impermeability. It is shown that Meridional Impermeability -- which provides a measure of the strength of the meridional mixing barrier as a function of potential vorticity (PV) gradient and wind-speed -- acts as a useful proxy for more complex metrics. In addition, Meridional Impermeability displays a well-defined vortex profile across equivalent latitude, which is not seen to the same degree in the other metrics assessed.  Representation of the ACV is further compared between climate models and reanalyses based on Meridional Impermeability. It is shown that while climate models have improved in their representation of the vortex barrier over time, there are still significant discrepancies between models and reanalyses. One cause of these discrepancies may result from the use of prescribed ozone fields rather than interactive ozone chemistry. This is further examined by comparing Chemistry Climate Model (CCM) simulations using interactive ozone chemistry, with those using prescribed ozone at either 3-D (i.e., height, latitude and longitude) or 2-D (i.e., height, latitude) dimensionality.   Considerable improvement in the representation of the ACV can be achieved by shifting from 2-D to 3-D prescribed ozone fields, and interactive ozone chemistry further improves its representation. However, discrepancies in model representation of the ACV still remain. Previous researchers have also attributed discrepancies in model representation of the polar vortices to the model resolution, and the parameterization of gravity waves at the sub-grid scale -- these factors are considered to contribute to the discrepancies found in simulations undertaken here also.   The results of this research are expected to provide guidance to improve the representation of vortex processes in climate modelling.</p>

scholarly journals Antarctic new particle formation from continental biogenic precursors

2012 ◽  
Vol 12 (12) ◽  
pp. 32741-32794 ◽  
Author(s):  
E.-M. Kyrö ◽  
V.-M. Kerminen ◽  
A. Virkkula ◽  
M. Dal Maso ◽  
J. Parshintsev ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Aerosol Formation ◽  
Nostoc Commune ◽  
Air Masses ◽  
Continental Antarctica ◽  
Antarctic Continent ◽  
Marine Areas ◽  
The Antarctic ◽  
First Time

Abstract. Over Antarctica, aerosol particles originate almost entirely from marine areas, with minor contribution from long-range transported dust or anthropogenic material. The Antarctic continent itself, unlike all other continental areas, has been thought to be practically free of aerosol sources. Here we present evidence of local aerosol production associated with melt-water ponds in the continental Antarctica. We show that in air masses passing such ponds, new aerosol particles are efficiently formed and these particles grow up to sizes where they may act as cloud condensation nuclei (CCN). The precursor vapours responsible for aerosol formation and growth originate very likely from highly abundant cyanobacteria Nostoc commune (Vaucher) communities of local ponds. This is the first time when freshwater vegetation has been identified as an aerosol precursor source. The influence of the new source on clouds and climate may increase in future Antarctica, and possibly elsewhere undergoing accelerating summer melting of semi-permanent snow cover.

scholarly journals Antarctic new particle formation from continental biogenic precursors

2013 ◽  
Vol 13 (7) ◽  
pp. 3527-3546 ◽  
Author(s):  
E.-M. Kyrö ◽  
V.-M. Kerminen ◽  
A. Virkkula ◽  
M. Dal Maso ◽  
J. Parshintsev ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Aerosol Particles ◽  
Aerosol Formation ◽  
Nostoc Commune ◽  
Air Masses ◽  
Continental Antarctica ◽  
Antarctic Continent ◽  
Marine Areas ◽  
The Antarctic ◽  
First Time

Abstract. Over Antarctica, aerosol particles originate almost entirely from marine areas, with minor contribution from long-range transported dust or anthropogenic material. The Antarctic continent itself, unlike all other continental areas, has been thought to be practically free of aerosol sources. Here we present evidence of local aerosol production associated with melt-water ponds in continental Antarctica. We show that in air masses passing such ponds, new aerosol particles are efficiently formed and these particles grow up to sizes where they may act as cloud condensation nuclei (CCN). The precursor vapours responsible for aerosol formation and growth originate very likely from highly abundant cyanobacteria Nostoc commune (Vaucher) communities of local ponds. This is the first time freshwater vegetation has been identified as an aerosol precursor source. The influence of the new source on clouds and climate may increase in future Antarctica, and possibly elsewhere undergoing accelerating summer melting of semi-permanent snow cover.

scholarly journals New particle formation in coastal New Zealand with a focus on open ocean air masses

2021 ◽  
Author(s):  
Maija Peltola ◽  
Clémence Rose ◽  
Jonathan V. Trueblood ◽  
Sally Gray ◽  
Mike Harvey ◽  
...  
Keyword(s):  
New Zealand ◽  
Particle Concentration ◽  
Particle Number ◽  
Particle Formation ◽  
Open Ocean ◽  
New Particle Formation ◽  
Air Masses ◽  
Wind Speeds ◽  
Marine Air ◽  
Aerosol Properties

Abstract. Even though oceans cover the majority of the Earth, most aerosol measurements are from continental sites. We measured aerosol particle number size distribution at Baring Head, in coastal New Zealand, over a total period of 10 months to study aerosol properties and new particle formation, with a special focus on aerosol formation in open ocean air masses. Particle concentrations were higher in land-influenced air compared to clean marine air in all size classes from sub-10 nm to cloud condensation nuclei sizes. When classifying the particle number size distributions with traditional methods designed for continental sites, new particle formation was observed at the station throughout the year with an average event frequency of 23 %. While most of these traditional event days had some land-influence, we also observed particle growth starting from nucleation mode during 16 % of the data in clean marine air and at least part of this growth was connected to nucleation in the marine boundary layer. Sub-10 nm particles accounted for 29 % of the total aerosol number concentration of particles larger than 1 nm in marine air during the spring. This shows that nucleation in marine air is frequent enough to influence the total particle concentration. Particle formation in land-influenced air was more intense and had on average higher growth rates than what was found for marine air. Particle formation and primary emissions increased particle number concentrations as a function of time spent over land during the first 1–2 days spent over land. After this, nucleation seems to start getting suppressed by the pre-existing particle population, but accumulation mode particle concentration keeps increasing, likely due to primary particle emissions. Further work showed that traditional NPF events were favoured by sunny conditions with low relative humidity and wind speeds. In marine air, formation of sub-10 nm particles was favoured by low temperatures, relative humidity, and wind speeds and could happen even during the night. Our future work will study the mechanisms responsible for particle formation at Baring Head with a focus on different chemical precursor species. This study sheds light on both new particle formation in open ocean air masses coming from the Southern Ocean and local aerosol properties in New Zealand.

Global variability of aerosol physical properties retrieved from the network of GAW near-surface observatories

2020 ◽  
Author(s):  
Clémence Rose ◽  
Keyword(s):  
Physical Properties ◽  
Particle Number ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Near Surface ◽  
Total Particle Number ◽  
Total Particle ◽  
Surface Measurements ◽  
Boundary Layer Dynamics ◽  
Aerosol Properties

&lt;p&gt;Due to their multiple effects on climate and human health, aerosol particles are a key component of the Earth&amp;#8217;s atmosphere. The understanding of these effects however remains incomplete, which in turn affects their quantification at the present time as well as future predictions. These limitations highlight the need for continuing the efforts to organize long term monitoring of the climate-relevant aerosol properties in as broad a network as possible.&lt;/p&gt;&lt;p&gt;The value of such measurements, which are performed in compliance with homogenous protocols and meet high quality standards, is clearly demonstrated in the present analysis. This work, which is focused on the particle number concentration and particle number size distribution (PNSD), is part of a wider project, one of the objectives of which is to document the variability of climate-relevant aerosol properties based on available in-situ near-surface measurements. To investigate the spatial variability of the abovementioned aerosol physical properties, observations collected at 57 sites connected to the Global Atmosphere Watch (GAW) network were analysed for a reference year (2017). Measurements performed with condensation particle counters (CPC, 21 sites) and mobility particle size spectrometers (MPSS, 36 sites) were both included in the analysis; in the latter case, the total particle number concentration, N&lt;sub&gt;tot&lt;/sub&gt;, was calculated over the diameter range 10 &amp;#8211; 500 nm.&lt;/p&gt;&lt;p&gt;As a result of enhanced sources, N&lt;sub&gt;tot&lt;/sub&gt; is generally higher during warmer seasons at all sites (in connection with atmospheric boundary layer dynamics for mountain sites). In addition, based on available MPSS data, the major contribution of Aitken mode particles (30-100 nm) to the total particle number concentration also appears as a common feature of all environments. In contrast, the observed levels of N&lt;sub&gt;tot&lt;/sub&gt;, between 10&lt;sup&gt;1&lt;/sup&gt; and 10&lt;sup&gt;4&lt;/sup&gt; cm&lt;sup&gt;-3&lt;/sup&gt;, and the magnitude of its seasonal cycle, exhibit, together with the variations of the PNSD, some distinctive behaviour for the different geographical categories and environmental footprint classes, with additional site-dependent characteristics. Among other factors (including the nature and proximity of the particles sources), the level of anthropogenic influence appears to strongly affect the observations.&lt;/p&gt;&lt;p&gt;This work will be completed in the near future with a trend analysis to document the temporal variability of the particle number concentration and PNSD.&lt;/p&gt;

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