scholarly journals High occurrence of new particle formation events at the Maïdo high-altitude observatory (2150 m), Réunion (Indian Ocean)

2018 ◽  
Vol 18 (13) ◽  
pp. 9243-9261 ◽  
Author(s):  
Brice Foucart ◽  
Karine Sellegri ◽  
Pierre Tulet ◽  
Clémence Rose ◽  
Jean-Marc Metzger ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Indian Ocean ◽  
Particle Growth ◽  
Threshold Value ◽  
Particle Formation ◽  
New Particle Formation ◽  
The Indian Ocean ◽  
Median Particle ◽  
Particle Sizer ◽  
The One

Abstract. This study aims to report and characterise the frequent new particle formation (NPF) events observed at the Maïdo observatory, Réunion, a Southern Hemisphere site located at 2150 m (a.s.l.) and surrounded by the Indian Ocean. From May 2014 to December 2015, continuous aerosol measurements were made using both a differential mobility particle sizer (DMPS) and an air ion spectrometer (AIS) to characterise the NPF events down to the lowest particle-size scale. Carbon monoxide (CO) and black carbon (BC) concentrations were monitored, as well as meteorological parameters, in order to identify the conditions that were favourable to the occurrence of nucleation in this specific environment. We point out that the annual NPF frequency average (65 %) is one of the highest reported so far. Monthly averages show a bimodal variation in the NPF frequency, with a maximum observed during transition periods (autumn and spring). A high yearly median particle growth rate (GR) of 15.16 nm h−1 is also measured showing a bimodal seasonal variation with maxima observed in July and November. Yearly medians of 2 and 12 nm particle formation rates (J2 and J12) are 0.858 and 0.508 cm−3 s−1, respectively, with a seasonal variation showing a maximum during winter, that correspond to low temperature and RH typical of the dry season, but also to high BC concentrations. We show that the condensation sink exceeds a threshold value (1.04×10−3 s−1) with a similar seasonal variation than the one of the NPF event frequency, suggesting that the occurrence of the NPF process might be determined by the availability of condensable vapours, which are likely to be transported together with pre-existing particles from lower altitudes.

scholarly journals High occurrence of new particle formation events at the Maïdo high altitude observatory (2150 m), Reunion Island (Indian Ocean)

2017 ◽  
Author(s):  
Brice Foucart ◽  
Karine Sellegri ◽  
Pierre Tulet ◽  
Clémence Rose ◽  
Jean-Marc Metzger ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Indian Ocean ◽  
Particle Growth ◽  
Particle Formation ◽  
Anthropogenic Sources ◽  
Reunion Island ◽  
New Particle Formation ◽  
Multiple Sources ◽  
Réunion Island ◽  
Particle Sizer

Abstract. This study aims to report and characterize the frequent new particle formation (NPF) events observed at the Maïdo observatory, Reunion Island, a Southern Hemisphere site located at 2200 m and surrounded by the Indian Ocean. In 2014 and 2015, continuous aerosol measurements were made using both a Differential Mobility Particle Sizer (DMPS) and an Air Ion Spectrometer (AIS) to characterize the NPF events down to the lowest particle size scale. Carbon monoxide (CO) and sulfur dioxide (SO2) concentrations were monitored, as well as meteorological parameters, in order to identify the conditions that were favourable to the occurrence of nucleation in this specific environment. We point out that the annual NPF frequency average (65 %) is one of the highest reported so far. Monthly averages show a bimodal variation of the NPF frequency, with a maximum observed during off-season periods (March to May and September to December). A high yearly median particle Growth Rate (GR) of 15.16 nm.h−1 is also measured, occasionally peaking at values of the order of 100 nm.h−1 and showing a bimodal seasonal variation with maxima observed in July and November. Yearly medians of 2 and 12 nm particle formation rates (J2 and J12) are 0.858 and 0.508 cm−3.s−1 respectively, with a seasonal variation similar to that of the GR. The seasonal variations of GR and J correspond to the seasonal variation of radiation, which may be responsible for more efficient photochemistry and also for a higher influence of the boundary layer, as shown by the CO seasonal variation. Multiple sources can contribute to the NPF frequency and intensity, including marine, biogenic from vegetation, and anthropogenic sources.

scholarly journals Analysis of particle size distribution changes between three measurement sites in Northern Scandinavia

2013 ◽  
Vol 13 (4) ◽  
pp. 9401-9442 ◽  
Author(s):  
R. Väänänen ◽  
E.-M. Kyrö ◽  
T. Nieminen ◽  
N. Kivekäs ◽  
H. Junninen ◽  
...  
Keyword(s):  
Particle Size ◽  
Size Distribution ◽  
Aerosol Particle ◽  
Particle Growth ◽  
Particle Formation ◽  
Aerosol Size Distribution ◽  
New Particle Formation ◽  
Air Masses ◽  
Aerosol Dynamics ◽  
Particle Sizer

Abstract. We investigated atmospheric aerosol particle dynamics in a boreal forest zone in Northern Scandinavia. We used aerosol size distribution data measured with either a Differential Mobility Particle Sizer (DMPS) or Scanning Mobility Particle Sizer (SMPS) at three stations (Värriö, Pallas and Abisko), and combined these data with the HYSPLIT air mass trajectory analysis. We compared three approaches: analysis of new particle formation events, investigation of air masses transport from the ocean to individual stations with different over-land transport times, and analysis of changes in aerosol particle size distributions during the air masses transport from one measurement station to another. Aitken mode particles were found to have an apparent average growth rate of 0.6–0.7 nm h−1 when the air masses travelled over land. Particle growth rates during the NPF events were 3–6 times higher than the apparent particle growth. When comparing aerosol dynamics between the different stations for different over-land transport times, no major differences were found except that in Abisko the new particle formation events were observed to take place in air masses having shorter over-land times than at the other stations. We speculate that this is related to the meteorological differences along the paths of air masses caused by the land surface topology. When comparing between air masses travelling the east-to-west direction to those traveling the west-to-east directions, clear differences in the aerosol dynamics were seen. Our results suggest that the condensation growth has an important role in aerosol dynamics also when new particle formation is not evident.

scholarly journals Modelling studies of HOMs and their contributions to new particle formation and growth: comparison of boreal forest in Finland and a polluted environment in China

2018 ◽  
Vol 18 (16) ◽  
pp. 11779-11791 ◽  
Author(s):  
Ximeng Qi ◽  
Aijun Ding ◽  
Pontus Roldin ◽  
Zhengning Xu ◽  
Putian Zhou ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Boreal Forest ◽  
Environmental Conditions ◽  
Eastern China ◽  
Particle Growth ◽  
Particle Formation ◽  
Forest Site ◽  
Polluted Environment ◽  
New Particle Formation ◽  
Multifunctional Compounds

Abstract. Highly oxygenated multifunctional compounds (HOMs) play a key role in new particle formation (NPF), but their quantitative roles in different environments of the globe have not been well studied yet. Frequent NPF events were observed at two “flagship” stations under different environmental conditions, i.e. a remote boreal forest site (SMEAR II) in Finland and a suburban site (SORPES) in polluted eastern China. The averaged formation rate of 6 nm particles and the growth rate of 6–30 nm particles were 0.3 cm−3 s−1 and 4.5 nm h−1 at SMEAR II compared to 2.3 cm−3 s−1 and 8.7 nm h−1 at SORPES, respectively. To explore the differences of NPF at the two stations, the HOM concentrations and NPF events at two sites were simulated with the MALTE-BOX model, and their roles in NPF and particle growth in the two distinctly different environments are discussed. The model provides an acceptable agreement between the simulated and measured concentrations of sulfuric acid and HOMs at SMEAR II. The sulfuric acid and HOM organonitrate concentrations are significantly higher but other HOM monomers and dimers from monoterpene oxidation are lower at SORPES compared to SMEAR II. The model simulates the NPF events at SMEAR II with a good agreement but underestimates the growth of new particles at SORPES, indicating a dominant role of anthropogenic processes in the polluted environment. HOMs from monoterpene oxidation dominate the growth of ultrafine particles at SMEAR II while sulfuric acid and HOMs from aromatics oxidation play a more important role in particle growth. This study highlights the distinct roles of sulfuric acid and HOMs in NPF and particle growth in different environmental conditions and suggests the need for molecular-scale measurements in improving the understanding of NPF mechanisms in polluted areas like eastern China.

scholarly journals Long-term analysis of clear-sky new particle formation events and non-events in Hyytiälä

2016 ◽  
Author(s):  
Lubna Dada ◽  
Pauli Paasonen ◽  
Tuomo Nieminen ◽  
Stephany Buenrostro Mazon ◽  
Jenni Kontkanen ◽  
...  
Keyword(s):  
Formation Rate ◽  
Threshold Value ◽  
Particle Formation ◽  
New Particle Formation ◽  
Organic Vapors ◽  
Clear Sky ◽  
Sky Conditions ◽  
Oxidized Products ◽  
Condensation Sink

Abstract. New particle formation (NPF) events have been observed all around the world and are known to be a major source of atmospheric aerosol particles. Here we combine 20 years of observations in a boreal forest at the SMEAR II station (Station for Measuring Ecosystem-Atmosphere Relations) in Hyytiälä, Finland, by utilizing previously accumulated knowledge, and by focusing on clear-sky (non-cloudy) conditions. We first investigated the effect of cloudiness on NPF and then compared the NPF event and non-event days during clear-sky conditions. In this comparison we considered, for example, the effects of calculated particle formation rates, condensation sink, trace gas concentrations and various meteorological quantities. The formation rate of 1.5 nm particles was calculated by using proxies for gaseous sulfuric acid and oxidized products of low volatile organic compounds. As expected, our results indicate an increase in the frequency of NPF events under clear-sky conditions. Also, focusing on clearsky conditions enabled us to find a clear separation of many variables related to NPF. For instance, oxidized organic vapors showed higher concentration during the clear-sky NPF event days, whereas the condensation sink (CS) and some trace gases had higher concentrations during the non-event days. The calculated formation rate of 3 nm particles showed a notable difference between the NPF event and non-event days during clear-sky conditions, especially in winter and spring. For spring time, we are able to find a threshold value for the combined values of ambient temperature and CS, above which practically no clear-sky NPF event could be observed. Finally, we present a probability distribution for the frequency of NPF events at a specific CS and temperature.

scholarly journals CCN production by new particle formation in the free troposphere

2017 ◽  
Vol 17 (2) ◽  
pp. 1529-1541 ◽  
Author(s):  
Clémence Rose ◽  
Karine Sellegri ◽  
Isabel Moreno ◽  
Fernando Velarde ◽  
Michel Ramonet ◽  
...  
Keyword(s):  
Particle Number ◽  
Particle Growth ◽  
Particle Formation ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Free Troposphere ◽  
New Particle Formation ◽  
Data Set ◽  
Radiative Processes ◽  
The Impact

Abstract. Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contributes significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, on Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to ∼ 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between 1 January and 31 December 2012, we found that 61 % of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF, relative to the transport and growth of pre-existing particles, to CCN size. The averaged production of 50 nm particles during those events was 5072, and 1481 cm−3 for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67 % against 53 % in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud-related radiative processes.

The African Diaspora

2013 ◽  
Author(s):  
John Parker
Keyword(s):  
African American ◽  
Indian Ocean ◽  
African Diaspora ◽  
Belief Systems ◽  
The United States ◽  
Cultural Transformation ◽  
Cultural Continuity ◽  
African Continent ◽  
The Indian Ocean ◽  
The One

In recent decades, research on the African diaspora has increasingly expanded from its established focus on the northern Atlantic to Latin America, the Indian Ocean, the Mediterranean world, and the African continent itself. This chapter discusses differing definitions of the diaspora, considers the role of pioneering scholars in early twentieth-century Cuba, Brazil, and the United States, and examines the debate between those who have stressed lines of cultural continuity between Africa and African American peoples, on the one hand, and those who have stressed cultural transformation or ‘creolization’ in the Americas, on the other. Recent research on African American religions has moved the field beyond the search for African origins by showing how the practitioners of these belief systems creatively and strategically imagined and reimagined ‘African’ ritual identities and Africa itself. Finally, the process of creolization in the African continent itself and in the Indian Ocean are considered.

scholarly journals New Particle Formation and impact on CCN concentrations in the boundary layer and free troposphere at the high altitude station of Chacaltaya (5240 m a.s.l.), Bolivia

2016 ◽  
Author(s):  
C. Rose ◽  
K. Sellegri ◽  
I. Moreno ◽  
F. Velarde ◽  
M. Ramonet ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Particle Number ◽  
Particle Growth ◽  
Particle Formation ◽  
Number Concentration ◽  
Particle Number Concentration ◽  
Free Troposphere ◽  
New Particle Formation ◽  
Radiative Processes ◽  
The Impact

Abstract. Global models predict that new particle formation (NPF) is, in some environments, responsible for a substantial fraction of the total atmospheric particle number concentration and subsequently contribute significantly to cloud condensation nuclei (CCN) concentrations. NPF events were frequently observed at the highest atmospheric observatory in the world, Chacaltaya (5240 m a.s.l.), Bolivia. The present study focuses on the impact of NPF on CCN population. Neutral cluster and Air Ion Spectrometer and mobility particle size spectrometer measurements were simultaneously used to follow the growth of particles from cluster sizes down to ~ 2 nm up to CCN threshold sizes set to 50, 80 and 100 nm. Using measurements performed between January 1 and December 31 2012, we found that 61% of the 94 analysed events showed a clear particle growth and significant enhancement of the CCN-relevant particle number concentration. We evaluated the contribution of NPF events relative to the transport of pre-existing particles to the site. The averaged production of 50 nm particles during those events was 5072 cm−3, and 1481 cm−3 for 100 nm particles, with a larger contribution of NPF compared to transport, especially during the wet season. The data set was further segregated into boundary layer (BL) and free troposphere (FT) conditions at the site. The NPF frequency of occurrence was higher in the BL (48 %) compared to the FT (39 %). Particle condensational growth was more frequently observed for events initiated in the FT, but on average faster for those initiated in the BL, when the amount of condensable species was most probably larger. As a result, the potential to form new CCN was higher for events initiated in the BL (67 % against 56 % in the FT). In contrast, higher CCN number concentration increases were found when the NPF process initially occurred in the FT, under less polluted conditions. This work highlights the competition between particle growth and the removal of freshly nucleated particles by coagulation processes. The results support model predictions which suggest that NPF is an effective source of CCN in some environments, and thus may influence regional climate through cloud related radiative processes.

scholarly journals Quantifying aerosol size distributions and their temporal variability in the Southern Great Plains, USA

2019 ◽  
Vol 19 (18) ◽  
pp. 11985-12006 ◽  
Author(s):  
Peter J. Marinescu ◽  
Ezra J. T. Levin ◽  
Don Collins ◽  
Sonia M. Kreidenweis ◽  
Susan C. van den Heever
Keyword(s):  
Size Distribution ◽  
Great Plains ◽  
Diurnal Cycle ◽  
Particle Formation ◽  
Aerosol Size Distribution ◽  
Size Distributions ◽  
New Particle Formation ◽  
Scanning Mobility Particle Sizer ◽  
Southern Great Plains ◽  
Particle Sizer

Abstract. A quality-controlled, 5-year dataset of aerosol number size distributions (particles with diameters (Dp) from 7 nm through 14 µm) was developed using observations from a scanning mobility particle sizer, aerodynamic particle sizer, and a condensation particle counter at the Department of Energy's Southern Great Plains (SGP) site. This dataset was used for two purposes. First, typical characteristics of the aerosol size distribution (number, surface area, and volume) were calculated for the SGP site, both for the entire dataset and on a seasonal basis, and size distribution lognormal fit parameters are provided. While the median size distributions generally had similar shapes (four lognormal modes) in all the seasons, there were some significant differences between seasons. These differences were most significant in the smallest particles (Dp<30 nm) and largest particles (Dp>800 nm). Second, power spectral analysis was conducted on this long-term dataset to determine key temporal cycles of total aerosol concentrations, as well as aerosol concentrations in specified size ranges. The strongest cyclic signal was associated with a diurnal cycle in total aerosol number concentrations that was driven by the number concentrations of the smallest particles (Dp<30 nm). This diurnal cycle in the smallest particles occurred in all seasons in ∼50 % of the observations, suggesting a persistent influence of new particle formation events on the number concentrations observed at the SGP site. This finding is in contrast with earlier studies that suggest new particle formation is observed primarily in the springtime at this site. The timing of peak concentrations associated with this diurnal cycle was shifted by several hours depending on the season, which was consistent with seasonal differences in insolation and boundary layer processes. Significant diurnal cycles in number concentrations were also found for particles with Dp between 140 and 800 nm, with peak concentrations occurring in the overnight hours, which were primarily associated with both nitrate and organic aerosol cycles. Weaker cyclic signals were observed for longer timescales (days to weeks) and are hypothesized to be related to the timescales of synoptic weather variability. The strongest periodic signals (3.5–5 and 7 d cycles) for these longer timescales varied depending on the season, with no cyclic signals and the lowest variability in the summer.

scholarly journals Climatology of new particle formation at Izaña mountain GAW observatory in the subtropical North Atlantic

2014 ◽  
Vol 14 (8) ◽  
pp. 3865-3881 ◽  
Author(s):  
M. I. García ◽  
S. Rodríguez ◽  
Y. González ◽  
R. D. García
Keyword(s):  
Sulfuric Acid ◽  
North Atlantic ◽  
Growth Rates ◽  
Particle Growth ◽  
Particle Formation ◽  
Dust Particles ◽  
New Particle Formation ◽  
Data Set ◽  
Mean Values ◽  
Condensation Sink

Abstract. A climatology of new particle formation (NPF) events at high altitude in the subtropical North Atlantic is presented. A 4-year data set (June 2008–June 2012), which includes number size distributions (10–600 nm), reactive gases (SO2, NOx, and O3), several components of solar radiation and meteorological parameters, measured at Izaña Global Atmosphere Watch (GAW) observatory (2373 m above sea level; Tenerife, Canary Islands) was analysed. NPF is associated with the transport of gaseous precursors from the boundary layer by orographic buoyant upward flows that perturb the low free troposphere during daytime. On average, 30% of the days contained an NPF event. Mean values of the formation and growth rates during the study period were 0.46 cm−3 s−1 and 0.42 nm h−1, correspondingly. There is a clearly marked NPF season (May–August), when these events account for 50–60% of the days per month. Monthly mean values of the formation and growth rates exhibit higher values in this season, 0.49–0.92 cm−3 s−1 and 0.48–0.58 nm h−1, respectively. During NPF events, SO2, UV radiation and upslope winds showed higher values than during non-events. The overall data set indicates that SO2 plays a key role as precursor, although other species seem to contribute during some periods. Condensation of sulfuric acid vapour accounts for most of the measured particle growth during most of the year (~70%), except for some periods. In May, the highest mean growth rates (~0.6 nm h−1) and the lowest contribution of sulfuric acid (~13%) were measured, suggesting a significant involvement of other condensing vapours. The SO2 availability seems also to be the most influencing parameter in the year-to-year variability in the frequency of NPF events. The condensation sink showed similar features to other mountain sites, showing high values during NPF events. Summertime observations, when Izaña is within the Saharan Air Layer, suggest that dust particles may play a significant role acting as coagulation sink of freshly formed nucleation particles. The contribution of dust particles to the condensation sink of sulfuric acid vapours seems to be modest (~8% as average). Finally, we identified a set of NPF events in which two nucleation modes, which may evolve at different rates, occur simultaneously and for which further investigations are necessary.

Seasonal variation in the long-term warming trend in water temperature off the Western Australian coast

2009 ◽  
Vol 60 (2) ◽  
pp. 129 ◽  
Author(s):  
N. Caputi ◽  
S. de Lestang ◽  
M. Feng ◽  
A. Pearce
Keyword(s):  
Seasonal Variation ◽  
Indian Ocean ◽  
Water Temperature ◽  
West Coast ◽  
Climate Models ◽  
Warming Trend ◽  
Temperature Cycle ◽  
Rock Lobster ◽  
Leeuwin Current ◽  
The Indian Ocean

Previous studies have demonstrated that one area of greatest increase in surface sea temperatures (SST) (0.02°C per year) in the Indian Ocean over the last 50 years occurs off the lower west coast of Australia, an area dominated by the Leeuwin Current. The present paper examines water temperature trends at several coastal sites since the early 1970s: two rock lobster puerulus monitoring sites in shallow water (<5 m); four sites from a monitoring program onboard rock lobster vessels that provide bottom water temperature (<36 m); and an environmental monitoring site at Rottnest (0–50 m depth). Two global SST datasets are also examined. These data show that there was a strong seasonal variation in the historic increases in temperature off the lower west coast of Australia, with most of the increases (0.02–0.035°C per year) only focussed on 4–6 months over the austral autumn–winter with little or no increase (<0.01°C per year) apparent in the austral spring–summer period. These increases are also apparent after taking into account the interannual variation in the strength of the Leeuwin Current. The warming trend results in a change to the seasonal temperature cycle over the decades, with a delay in the peak in the temperature cycle during autumn between the 1950s and 2000s of ~10–20 days. A delay in the timing of the minimum temperature is also apparent at Rottnest from August–September to October. This seasonal variation in water temperature increases and its effect on the annual temperature cycle should be examined in climate models because it provides the potential to better understand the specific processes through which climate change and global warming are affecting this region of the Indian Ocean. It also provides an opportunity to further test the climate models to see whether this aspect is predicted in the future projections of how increases will be manifest. Any seasonal variation in water temperature increase has important implications for fisheries and the marine ecosystem because it may affect many aspects of the annual life cycle such as timing of growth, moulting, mating, spawning and recruitment, which have to be taken into account in the stock assessment and management of fisheries.

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