scholarly journals Seasonal variation of aerosol size distributions in the free troposphere and residual layer at the puy de Dôme station, France

2009 ◽  
Vol 9 (4) ◽  
pp. 1465-1478 ◽  
Author(s):  
H. Venzac ◽  
K. Sellegri ◽  
P. Villani ◽  
D. Picard ◽  
P. Laj
Keyword(s):  
Boundary Layer ◽  
Seasonal Variation ◽  
Size Distribution ◽  
Seasonal Variability ◽  
Number Concentration ◽  
Residual Layer ◽  
Size Distributions ◽  
Free Troposphere ◽  
Air Mass ◽  
Aerosol Sources

Abstract. Particle number concentration and size distribution are important variables needed to constrain the role of atmospheric particles in the Earth radiation budget, both directly and indirectly through CCN activation. They are also linked to regulated variables such as particle mass (PM) and therefore of interest to air quality studies. However, data on their long-term variability are scarce, in particular at high altitudes. In this paper, we investigate the diurnal and seasonal variability of the aerosol total number concentration and size distribution at the puy de Dôme research station (France, 1465 m a.s.l.). We report a variability of aerosol particle total number concentration measured over a five-year (2003–2007) period for particles larger than 10 nm and aerosol size distributions between 10 and 500 nm over a two-year period (January 2006 to December 2007). Concentrations show a strong seasonality with maxima during summer and minima during winter. A diurnal variation is also observed with maxima between 12:00 and 18:00 UTC. At night (00:00–06:00 UTC), the median hourly total concentration varies from 600 to 800 cm−3 during winter and from 1700 to 2200 cm−3 during summer. During the day (08:00–18:00 UTC), the concentration is in the range of 700 to 1400 cm−3 during winter and of 2500 to 3500 cm−3 during summer. An averaged size distribution of particles (10–500 nm) was calculated for each season. The total aerosol number concentrations are dominated by the Aitken mode integral concentrations, which drive most of the winter to summer total concentrations increase. The night to day increase in dominated by the nucleation mode integral number concentration. Because the site is located in the free troposphere only a fraction of the time, in particular at night and during the winter season, we have subsequently analyzed the variability for nighttime and free tropospheric (FT)/residual layer (RL) conditions only. We show that a seasonal variability is still observed for these FT/RL conditions. The FT/RL seasonal variation is due to both seasonal changes in the air mass origin from winter to summer and enhanced concentrations of particles in the residual layer/free troposphere in summer. The later observation can be explained by higher emissions intensity in the boundary layer, stronger exchanges between the boundary layer and the free troposphere as well as enhanced photochemical processes. Finally, aerosols mean size distributions are calculated for a given air mass type (marine/continental/regional) according to the season for the specific conditions of the residual layer/free troposphere. The seasonal variability in aerosol sources seems to be predominant over the continent compared to the seasonal variation of marine aerosol sources. These results are of regional relevance and can be used to constrain chemical-transport models over Western Europe.

scholarly journals Seasonal variation of aerosol size distribution at Puy de Dôme (1465 m a.s.l., central France)

2008 ◽  
Vol 8 (4) ◽  
pp. 15791-15824 ◽  
Author(s):  
H. Venzac ◽  
K. Sellegri ◽  
P. Villani ◽  
D. Picard ◽  
P. Laj
Keyword(s):  
Boundary Layer ◽  
Size Distribution ◽  
Total Concentration ◽  
Winter Season ◽  
Number Concentration ◽  
Aerosol Size Distribution ◽  
Research Station ◽  
Size Distributions ◽  
Free Troposphere ◽  
Air Mass

Abstract. Particle number concentration and size distribution are amongst the most important variables needed to constrain the role of the atmospheric particles in the Earth radiative budget. They are also linked to regulated variables such as particle mass (PM) and therefore of interest to air quality studies. However, data on their long-term variability are scarce, in particular at high altitudes where the occurrence of aerosol in elevated layers cannot be resolved from most instruments in space. Therefore it is crucial to provide ground based measurements of suited aerosol variables to obtain closure between all independent information sources. In this paper, we investigate diurnal and seasonal variability of aerosol number concentration and size distribution at the Puy de Dôme research station (France, 1465 m a.s.l.). We report variability of aerosol particle total number concentration measured over a five years (2003–2007) period and aerosol size distributions over a one year period (January to December 2006). Concentrations show a strong seasonality with maxima during summer and minima during winter. A diurnal variation is also observed with maxima between 12:00 and 18:00 UTC. At night (00:00–06:00 UTC), the median hourly total concentration varies from 600 to 800 cm−3 during winter and from 1700 to 2200 cm−3 during summer. During the day (08:00–18:00 UTC), the concentration is in the range of 700 to 1400 cm−3 during winter and from 2500 to 3500 cm−3 during summer. An averaged size distribution of particles (10–500 nm) was calculated for each season. A variability in the size of aerosols sampled at the Puy de Dôme is also observed on the seasonal and diurnal basis. Because the site lies in the free troposphere only a fraction of the time, in particular at night and during the winter season, we have subsequently analyzed the variability for free tropospheric conditions only. We show that the variability is due to both seasonal changes in air mass origin from winter to summer and enhanced concentration of the free troposphere in summer. The later observation can be explained by higher emission intensity in the boundary layer, stronger exchange between the boundary layer and the free troposphere as well as enhanced photochemical processes. Finally, aerosol mean size distributions are calculated for a given air mass type (marine/continental/regional) according to the season, for the specific conditions of the free troposphere. These results are of regional relevance and can be used to constrain chemical-transport models over Western Europe.

scholarly journals The lofting of Western Pacific regional aerosol by island thermodynamics as observed around Borneo

2012 ◽  
Vol 12 (13) ◽  
pp. 5963-5983 ◽  
Author(s):  
N. H. Robinson ◽  
J. D. Allan ◽  
J. A. Trembath ◽  
P. D. Rosenberg ◽  
G. Allen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sea Breeze ◽  
Number Concentration ◽  
Western Pacific ◽  
Surface Mixed Layer ◽  
Free Troposphere ◽  
Mean Flow ◽  
Aerosol Composition ◽  
Air Mass ◽  
The Western Pacific

Abstract. Vertical profiles of aerosol chemical composition, number concentration and size were measured throughout the lower troposphere of Borneo, a large tropical island in the western Pacific Ocean. Aerosol composition, size and number concentration measurements (using an Aerodyne Aerosol Mass Spectrometer, Passive Cavity Aerosol Spectrometer Probe and Condensation Particle Counter, respectively) were made both upwind and downwind of Borneo, as well as over the island itself, on board the UK BAe-146 research aircraft as part of the OP3 project. Two meteorological regimes were identified – one dominated by isolated terrestrial convection (ITC) which peaked in the afternoon, and the other characterised by more regionally active mesoscale convective systems (MCS). Upwind profiles show aerosol to be confined to a shallow marine boundary layer below 930 ± 10 hPa (~760 m above sea level, a.s.l.). As this air mass advects over the island with the mean free troposphere synoptic flow during the ITC-dominated regime, it is convectively lofted above the terrestrial surface mixed layer to heights of between 945 ± 22 (~630 m a.s.l.) and 740 ± 44 hPa (~2740 m a.s.l.), consistent with a coupling between the synoptic steering level flow and island sea breeze circulations. Terrestrial aerosol was observed to be lofted into this higher layer through both moist convective uplift and transport through turbulent diurnal sea-breeze cells. At the peak of convective activity in the mid-afternoons, organic aerosol loadings in the lofted layer were observed to be substantially higher than in the morning (by a mean factor of three). This organic matter is dominated by secondary aerosol from processing of biogenic gas phase precursors. Aerosol number concentration profiles suggest formation of new particles aloft in the atmosphere. By the time the air mass reaches the west coast of the island, terrestrial aerosol is enhanced in the lofted layer. Such uplift of aerosol in Borneo is expected to increase aerosol lifetimes in the lower free troposphere downwind, as they are above the boundary layer and therefore less likely to be lost by wet or dry deposition. It is also likely to change the role they play in the semi-direct and direct aerosol effects. The long chain of islands extending from Malaysia to Australia may all similarly be expected to present an orographic barrier to low level mean flow. This would lead to significant transport of aerosol into the tropical free troposphere across the Western Pacific region.

scholarly journals Seasonal variations of aerosol size distributions based on long-term measurements at the high altitude Himalayan site of Nepal Climate Observatory-Pyramid (5079 m), Nepal

2010 ◽  
Vol 10 (21) ◽  
pp. 10679-10690 ◽  
Author(s):  
K. Sellegri ◽  
P. Laj ◽  
H. Venzac ◽  
J. Boulon ◽  
D. Picard ◽  
...  
Keyword(s):  
Seasonal Variability ◽  
Monsoon Season ◽  
Number Concentration ◽  
Residual Layer ◽  
Research Station ◽  
Free Troposphere ◽  
Night Time ◽  
High Accumulation ◽  
Air Masses ◽  
Post Monsoon

Abstract. The present paper investigates the diurnal and seasonal variability of the aerosol total number concentration, number and volume size distribution between 10 nm and 10 μm, from a combination of a scanning mobility particle sizer (SMPS) and an optical counter (OPC), performed over a two-year period (January 2006–February 2008) at the Nepal Climate Observatory-Pyramid (NCO-P) research station, (5079 m a.s.l.). The annual average number concentration measured over the two-year period at the NCO-P is 860 cm−3. Total concentrations show a strong seasonality with maxima during pre-monsoon and post-monsoon seasons and minima during the dry and monsoon seasons. A diurnal variation is also clearly observed, with maxima between 09:00 and 12:00 UTC. The aerosol concentration maxima are mainly due to nucleation processes during the post-monsoon season, as witnessed by high nucleation mode integrated number concentrations, and to transport of high levels of pollution from the plains by valley breezes during the pre-monsoon season, as demonstrated by high accumulation mode integrated number concentrations. Night-time number concentration of particles (from 03:00 to 08:00 NST) are relatively low throughout the year (from 450 cm−3 during the monsoon season to 675 cm−3 during the pre-monsoon season), indicating the of high altitudes background level, as a result of downslope winds during this part of the day. However, it was found that these background concentrations are strongly influenced by the daytime concentrations, as they show the same seasonal variability. If nighttime concentrations were presumed to be representative of free troposphere (FT)/residual layer concentrations, they would be found to be two times higher than at other lower altitudes European sites, such as the Jungfraujoch. However, BL intrusions might contaminate the free troposphere/residual layer even at this altitude, especially during regional air masses influence. Night-time measurements were subsequently selected to study the FT composition according to different air masses, and the effect of long range transport to the station.

scholarly journals Seasonal Variation of Aerosol Size Distribution Data at the Puy de Dôme Station with Emphasis on the Boundary Layer/Free Troposphere Segregation

Atmosphere ◽  
2018 ◽  
Vol 9 (7) ◽  
pp. 244 ◽  
Author(s):  
Antoine Farah ◽  
Evelyn Freney ◽  
Aurélien Chauvigné ◽  
Jean-Luc Baray ◽  
Clémence Rose ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Seasonal Variation ◽  
Size Distribution ◽  
Aerosol Size Distribution ◽  
Distribution Data ◽  
Free Troposphere

scholarly journals The lofting of Western Pacific regional aerosol by island thermodynamics as observed around Borneo

2012 ◽  
Vol 12 (1) ◽  
pp. 1215-1265 ◽  
Author(s):  
N. H. Robinson ◽  
J. D. Allan ◽  
J. A. Trembath ◽  
P. D. Rosenberg ◽  
G. Allen ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Sea Breeze ◽  
Number Concentration ◽  
Western Pacific ◽  
Surface Mixed Layer ◽  
Free Troposphere ◽  
Mean Flow ◽  
Aerosol Composition ◽  
Air Mass ◽  
The Western Pacific

Abstract. Vertical profiles of aerosol chemical composition, number concentration and size were measured throughout the lower troposphere of Borneo, a large tropical island in the western Pacific Ocean. Aerosol composition, size and number concentration measurements (using an Aerodyne Aerosol Mass Spectrometer, Passive Cavity Aerosol Spectrometer Probe and Condensation Particle Counter, respectively) were made both upwind and downwind of Borneo, as well as over the island itself, on board the UK BAe-146 research aircraft as part of the OP3 project. Two meteorological regimes were identified – one dominated by isolated terrestrial convection (ITC) which peaked in the afternoon, and the other characterised by more regionally active mesoscale convective systems (MCS). Upwind profiles show aerosol to be confined to a shallow marine boundary layer below 930 ± 10 hPa (~760 m above sea level, a.s.l.). As this air mass advects over the island with the mean free troposphere synoptic flow during the ITC-dominated regime, it is convectively lofted above the terrestrial surface mixed layer to heights of between 945 ± 22 (~630 m a.s.l.) and 740 ± 44 hPa (~2740 m a.s.l.), consistent with a coupling between the synoptic steering level flow and island sea breeze circulations. Terrestrial aerosol was observed to be lofted into this higher layer through both moist convective uplift and transport through turbulent diurnal sea-breeze cells. At the peak of convective activity in the mid-afternoons, organic aerosol loadings in the lofted layer were observed to be substantially higher than in the morning (by a mean factor of three). This organic matter is dominated by secondary aerosol from processing of biogenic gas phase precursors. Aerosol number concentration profiles suggest formation of new particles aloft in the atmosphere. By the time the air mass reaches the west coast of the island, terrestrial aerosol is enhanced in the lofted layer. Such uplift of aerosol in Borneo is expected to increase aerosol lifetimes in the lower free troposphere downwind, as they are above the boundary layer and therefore less likely to be lost by wet or dry deposition. It is also likely to change the role they play in the semi-direct and direct aerosol effects. The long chain of islands extending from Malaysia to Australia may all similarly be expected to present an orographic barrier to low level mean flow. This would lead to significant transport of aerosol into the tropical free troposphere across the Western Pacific region.

scholarly journals Aerosol characteristics in the entrainment interface layer in relation to the marine boundary layer and free troposphere

2018 ◽  
Vol 18 (3) ◽  
pp. 1495-1506 ◽  
Author(s):  
Hossein Dadashazar ◽  
Rachel A. Braun ◽  
Ewan Crosbie ◽  
Patrick Y. Chuang ◽  
Roy K. Woods ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Size Distribution ◽  
Surface Area ◽  
Particle Number ◽  
Interface Layer ◽  
Number Concentration ◽  
Aerosol Size Distribution ◽  
Free Troposphere ◽  
Turbulent Layer ◽  
Concentration Difference

Abstract. This study uses airborne data from two field campaigns off the California coast to characterize aerosol size distribution characteristics in the entrainment interface layer (EIL), a thin and turbulent layer above marine stratocumulus cloud tops, which separates the stratocumulus-topped boundary layer (STBL) from the free troposphere (FT). The vertical bounds of the EIL are defined in this work based on considerations of buoyancy and turbulence using thermodynamic and dynamic data. Aerosol number concentrations are examined from three different probes with varying particle diameter (Dp) ranges: > 3 nm, > 10 nm, and 0.11–3.4 µm. Relative to the EIL and FT layers, the sub-cloud (SUB) layer exhibited lower aerosol number concentrations and higher surface area concentrations. High particle number concentrations between 3 and 10 nm in the EIL are indicative of enhanced nucleation, assisted by high actinic fluxes, cool and moist air, and much lower surface area concentrations than the STBL. Slopes of number concentration versus altitude in the EIL were correlated with the particle number concentration difference between the SUB and lower FT layers. The EIL aerosol size distribution was influenced by varying degrees from STBL aerosol versus subsiding FT aerosol depending on the case examined. These results emphasize the important role of the EIL in influencing nucleation and aerosol–cloud–climate interactions.

scholarly journals Aerosol Characteristics in the Entrainment Interface Layer In Relation to the Marine Boundary Layer and Free Troposphere

2017 ◽  
Author(s):  
Hossein Dadashazar ◽  
Rachel A. Braun ◽  
Ewan Crosbie ◽  
Patrick Y. Chuang ◽  
Roy K. Woods ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Size Distribution ◽  
Surface Area ◽  
Particle Number ◽  
Interface Layer ◽  
Number Concentration ◽  
Aerosol Size Distribution ◽  
Free Troposphere ◽  
Turbulent Layer ◽  
Concentration Difference

Abstract. This study uses airborne data from two field campaigns off the California coast to characterize aerosol size distribution characteristics in the entrainment interface layer (EIL), a thin and turbulent layer above marine stratocumulus cloud tops, that separates the stratocumulus-topped boundary layer (STBL) from the free troposphere (FT). The vertical bounds of the EIL are defined in this work based on considerations of buoyancy and turbulence using thermodynamic and dynamic data. Aerosol number concentrations are examined from three different probes with varying particle diameter (Dp) ranges: > 3 nm, > 10 nm, 0.11–3.4 µm. Relative to the EIL and FT layers, the sub-cloud (SUB) layer exhibited lower aerosol number concentrations and higher surface area concentrations. High particle number concentrations between 3 and 10 nm in the EIL is indicative of enhanced nucleation, assisted by high actinic fluxes, cool and moist air, and much lower surface area concentrations than the STBL. Slopes of number concentration versus altitude in the EIL were correlated with the particle number concentration difference between the SUB and lower FT layers. The EIL aerosol size distribution was influenced by varying degrees from STBL aerosol versus subsiding FT aerosol depending on the case examined. These results emphasize the important role of the EIL in influencing nucleation and aerosol-cloud-climate interactions.  

scholarly journals Sub-seasonal Variability in the Boundary Layer Sources for Transport into the Tropopause Layer in the Asian Monsoon Region

2017 ◽  
Author(s):  
Bin Chen ◽  
Bärbel Vogel ◽  
Xiangde Xu ◽  
Shuai Yang
Keyword(s):  
Boundary Layer ◽  
Tibetan Plateau ◽  
Mass Transport ◽  
Seasonal Variability ◽  
The Tibetan Plateau ◽  
Southern Slope ◽  
Seasonal Behavior ◽  
Air Mass ◽  
Source Regions ◽  
Wide Range

Abstract. The Asian summer monsoon (ASM) is associated with an upper-level anticyclone and acts as a well-recognized conduit for troposphere-to-stratosphere transport. The Lagrangian dispersion and transport model FLEXPART forced by ERA-Interim data from 2001–2013 was used to perform climatological modeling of the summer season (May–July). This study examines the properties of the air mass transport from the atmospheric boundary layer (BL) to the tropopause layer (TL), with particular focus on the sub-seasonal variability in the tracer-independent BL sources and the potential controlling mechanisms. The results show that, climatologically, the three most impactful BL source regions are northern India, the Tibetan Plateau, and the southern slope of the Himalayas. These regions are consistent with the locations of sources identified in previous studies. However, upon closer inspection, the different source regions to the BL-to-TL air mass transport are not constant in location or shape and are strongly affected by sub-seasonal variability. The contributions from the Tibetan Plateau are most significant in early May but decrease slightly in mid-May to mid-June. In contrast, the contributions from India and the southern slope of the Himalayas increase dramatically, with peak values occurring in mid-July. Empirical Orthogonal Function (EOF) analysis provides further evidence that the BL sources in the ASM region vary across a wide range of spatiotemporal scales. The sub-seasonal behavior of these BL sources is closely related to the strength of persistent deep convection activity over the northern Bay of Bengal and its neighboring areas.

scholarly journals Multivariate statistical air mass classification for the high-alpine observatory at the Zugspitze Mountain, Germany

2019 ◽  
Vol 19 (19) ◽  
pp. 12477-12494 ◽  
Author(s):  
Armin Sigmund ◽  
Korbinian Freier ◽  
Till Rehm ◽  
Ludwig Ries ◽  
Christian Schunk ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Real Time ◽  
Statistical Approach ◽  
Free Troposphere ◽  
Time Data ◽  
Detection Scheme ◽  
Air Mass ◽  
Thermally Induced ◽  
Air Masses ◽  
Mechanistic Approach

Abstract. To assist atmospheric monitoring at high-alpine sites, a statistical approach for distinguishing between the dominant air masses was developed. This approach was based on a principal component analysis using five gas-phase and two meteorological variables. The analysis focused on the Schneefernerhaus site at Zugspitze Mountain, Germany. The investigated year was divided into 2-month periods, for which the analysis was repeated. Using the 33.3 % and 66.6 % percentiles of the first two principal components, nine air mass regimes were defined. These regimes were interpreted with respect to vertical transport and assigned to the BL (recent contact with the boundary layer), UFT/SIN (undisturbed free troposphere or stratospheric intrusion), and HYBRID (influences of both the boundary layer and the free troposphere or ambiguous) air mass classes. The input data were available for 78 % of the investigated year. BL accounted for 31 % of the cases with similar frequencies in all seasons. UFT/SIN comprised 14 % of the cases but was not found from April to July. HYBRID (55 %) mostly exhibited intermediate characteristics, whereby 17 % of the HYBRID class suggested an influence from the marine boundary layer or the lower free troposphere. The statistical approach was compared to a mechanistic approach using the ceilometer-based mixing layer height from a nearby valley site and a detection scheme for thermally induced mountain winds. Due to data gaps, only 25 % of the cases could be classified using the mechanistic approach. Both approaches agreed well, except in the rare cases of thermally induced uplift. The statistical approach is a promising step towards a real-time classification of air masses. Future work is necessary to assess the uncertainty arising from the standardization of real-time data.

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.

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