scholarly journals Airborne observations of trace gases over boreal Canada during BORTAS: campaign climatology, air mass analysis and enhancement ratios

2013 ◽  
Vol 13 (24) ◽  
pp. 12451-12467 ◽  
Author(s):  
S. J. O'Shea ◽  
G. Allen ◽  
M. W. Gallagher ◽  
S. J.-B. Bauguitte ◽  
S. M. Illingworth ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Biomass Burning ◽  
Dry Matter ◽  
Emission Factors ◽  
Far Field ◽  
Air Mass ◽  
Air Masses ◽  
Airborne Measurements ◽  
Northwestern Ontario ◽  
The Impact

Abstract. In situ airborne measurements were made over eastern Canada in summer 2011 as part of the BORTAS experiment (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites). In this paper we present observations of greenhouse gases (CO2 and CH4) and other biomass burning tracers (CO, HCN and CH3CN), both climatologically and through case studies, as recorded on board the FAAM BAe-146 research aircraft. Vertical profiles of CO2 were generally characterised by depleted boundary layer concentrations relative to the free troposphere, consistent with terrestrial biospheric uptake. In contrast, CH4 concentrations were found to rise with decreasing altitude due to strong local and regional surface sources. BORTAS observations were found to be broadly comparable with both previous measurements in the region during the regional burning season and with reanalysed composition fields from the EU Monitoring Atmospheric Composition and Change (MACC) project. We use coincident tracer–tracer correlations and a Lagrangian trajectory model to characterise and differentiate air mass history of intercepted plumes. In particular, CO, HCN and CH3CN were used to identify air masses that have been recently influenced by biomass burning. Examining individual cases we were able to quantify emissions from biomass burning. Using both near-field (< 1 day) and far-field (> 1 day) sampling, boreal forest fire plumes were identified throughout the troposphere. Fresh plumes from fires in northwestern Ontario yield emission factors for CH4 and CO2 of 8.5 ± 0.9 g (kg dry matter)−1 and 1512 ± 185 g (kg dry matter)−1, respectively. We have also investigated the efficacy of calculating emission factors from far-field sampling, in which there might be expected to be limited mixing with background and other characteristic air masses, and we provide guidance on best practice and limitations in such analysis. We have found that for measurements within plumes that originated from fires in northwestern Ontario 2–4 days upwind, emission factors can be calculated that range between 1618 ± 216 and 1702 ± 173 g (kg dry matter)−1 for CO2 and 1.8 ± 0.2 and 6.1 ± 1 g (kg dry matter)−1 for CH4.

scholarly journals Airborne observations of trace gases over boreal Canada during BORTAS: campaign climatology, airmass analysis and enhancement ratios

2013 ◽  
Vol 13 (5) ◽  
pp. 14069-14114 ◽  
Author(s):  
S. J. O'Shea ◽  
G. Allen ◽  
M. W. Gallagher ◽  
S. J.-B. Bauguitte ◽  
S. M. Illingworth ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Case Studies ◽  
Biomass Burning ◽  
Dry Matter ◽  
Trace Gases ◽  
Emission Factors ◽  
Far Field ◽  
Air Masses ◽  
Fire Plumes ◽  
Northwest Ontario

Abstract. In situ airborne measurements were made over Eastern Canada in summer 2011 as part of the BORTAS experiment (Quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and~Satellites). In this paper we present observations of greenhouse gases (CO2 and CH4) and other biomass burning tracers and related trace gases, both climatologically and through case studies, as recorded on board the FAAM BAe-146 research aircraft. Vertical profiles of CO2 were generally characterised by depleted boundary layer concentrations relative to the free troposphere, consistent with terrestrial biospheric uptake. In contrast, CH4 concentrations were found to rise with decreasing altitude due to strong local and regional surface sources. We use coincident tracer-tracer correlations and a Lagrangian trajectory model to characterise and differentiate air mass history of intercepted plumes. In particular, CO, HCN and CH3CN were used to identify air masses that have been recently influenced by biomass burning. Concentrations of CO2 were found to have a mean tropospheric, campaign-average concentration of 384.8 ppm (ranging between 371.5 and 397.1 ppm), whilst CH4 concentrations had a mean value of 1859 ppb (ranging between 1797 and 1968 ppb), representing the episodic sampling of local fire plumes. CH4 and CO2 concentrations during BORTAS were found to be broadly comparable to previous measurements in the region during the regional burning season and with reanalysed composition fields from the EU Monitoring Atmospheric Composition and Change (MACC) project. By examining individual case studies we were able to quantify emissions from biomass burning. Using both near-field (<1 day) and far-field (>1 day) sampling, boreal forest fire plumes were identified throughout the troposphere. Fresh plumes from fires in Northwest Ontario yield emission factors for CH4 and CO2 of 8.5 ± 0.9 g (kg dry matter)−1 and 1512 g ± 185 g (kg dry matter)−1, respectively. We have also investigated the efficacy of calculating emission factors from far-field sampling, in which there might be expected to be limited mixing with background and other characteristic air masses and we provide guidance on best practice and limitations in such analysis. We have found that for measurements within plumes that originated from fires in Northwest Ontario 2–4 days upwind, emission factors can be calculated that range between 1618 ± 216 and 1702 ± 173 g (kg dry matter)−1 for CO2 and 1.8 ± 0.2 and 6.1± 1 g (kg dry matter)−1 for CH4.

scholarly journals Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires

2014 ◽  
Vol 14 (18) ◽  
pp. 25095-25138 ◽  
Author(s):  
M. D. Jolleys ◽  
H. Coe ◽  
G. McFiggans ◽  
J. W. Taylor ◽  
S. J. O'Shea ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Biomass Burning ◽  
Forest Fires ◽  
Spatial Scales ◽  
Near Field ◽  
Organic Aerosol ◽  
Charge Ratio ◽  
Far Field ◽  
Airborne Measurements ◽  
The Impact

Abstract. Airborne measurements of biomass burning organic aerosol (BBOA) from boreal forest fires reveal highly contrasting properties for plumes of different ages. These measurements, performed using an Aerodyne Research Inc. compact time-of-flight aerosol mass spectrometer (C-ToF-AMS) during the BORTAS (quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment in the summer of 2011, have been used to derive normalised excess organic aerosol (OA) mass concentrations (ΔOA/ΔCO), with higher average ratios observed closer to source (0.190 ± 0.010) than in the far-field (0.097 ± 0.002). The difference in ΔOA/ΔCO between fresh and aged plumes is influenced by a change in dominant combustion conditions throughout the campaign. Measurements at source sampled largely smouldering fires, while plumes encountered in the far-field originated from fires occurring earlier in the campaign when fire activity had been more intense. Changing combustion conditions also affect the vertical distribution of biomass burning emissions, as aged plumes from more flaming-dominated fires are injected to higher altitudes of up to 6000 m. Proportional contributions of the mass-to-charge ratio (m/z) 60 and 44 peaks in the AMS mass spectra to the total OA mass (denoted f60 and f44) are used as tracers for primary and oxidized BBOA, respectively. Given the shorter aging times associated with near-field plumes, f44 is lower on average than in more aged, transported plumes. However, high levels of ΔO3/ΔCO and -log(NOx/NOy) close to source indicate that emissions can be subject to very rapid oxidation over short timescales. Conversely, the lofting of plumes into the upper troposphere can lead to the retention of source profiles after transportation over extensive temporal and spatial scales, with f60 also higher on average in aged plumes. Evolution of OA composition with aging is comparable to observations of BB tracers in previous studies, revealing a consistent progression from f60 to f44. The elevated levels of oxygenation in aged plumes, and their association with lower average ΔOA/ΔCO, highlight the influence of OA losses during aging, although there remain considerable uncertainties regarding the role of combustion processes on BBOA production and composition.

scholarly journals Properties and evolution of biomass burning organic aerosol from Canadian boreal forest fires

2015 ◽  
Vol 15 (6) ◽  
pp. 3077-3095 ◽  
Author(s):  
M. D. Jolleys ◽  
H. Coe ◽  
G. McFiggans ◽  
J. W. Taylor ◽  
S. J. O'Shea ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Biomass Burning ◽  
Forest Fires ◽  
Spatial Scales ◽  
Near Field ◽  
Organic Aerosol ◽  
Charge Ratio ◽  
Far Field ◽  
Airborne Measurements ◽  
The Impact

Abstract. Airborne measurements of biomass burning organic aerosol (BBOA) from boreal forest fires reveal highly contrasting properties for plumes of different ages. These measurements, performed using an Aerodyne Research Inc. compact time-of-flight aerosol mass spectrometer (C-ToF-AMS) during the BORTAS (quantifying the impact of BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites) experiment in the summer of 2011, have been used to derive normalised excess organic aerosol (OA) mass concentrations (ΔOA / ΔCO), with higher average ratios observed closer to source (0.190±0.010) than in the far-field (0.097±0.002). The difference in ΔOA / ΔCO between fresh and aged plumes is influenced by a change in dominant combustion conditions throughout the campaign. Measurements at source comprised 3 plume interceptions during a single research flight and sampled largely smouldering fires. Twenty-three interceptions were made across four flights in the far-field, with plumes originating from fires occurring earlier in the campaign when fire activity had been more intense, creating an underlying contrast in emissions prior to any transformations associated with aging. Changing combustion conditions also affect the vertical distribution of biomass burning emissions, as aged plumes from more flaming-dominated fires are injected to higher altitudes of up to 6000 m. Proportional contributions of the mass-to-charge ratio (m/z) 60 and 44 peaks in the AMS mass spectra to the total OA mass (denoted f60 and f44) are used as tracers for primary and oxidised BBOA, respectively. f44 is lower on average in near-field plumes than those sampled in the far-field, in accordance with longer aging times as plumes are transported a greater distance from source. However, high levels of ΔO3 / ΔCO and −log(NOx / NOy) close to source indicate that emissions can be subject to very rapid oxidation over short timescales. Conversely, the lofting of plumes into the upper troposphere can lead to the retention of source profiles after transportation over extensive temporal and spatial scales, with f60 also higher on average in aged plumes. Evolution of OA composition with aging is comparable to observations of BB tracers in previous studies, revealing a consistent progression from f60 to f44. The elevated levels of oxygenation in aged plumes, and their association with lower average ΔOA / ΔCO, are consistent with OA loss through evaporation during aging due to a combination of dilution and chemical processing, while differences in combustion conditions throughout the campaign also have a significant influence on BBOA production and composition.

scholarly journals Airborne observations and modeling of springtime stratosphere-to-troposphere transport over California

2013 ◽  
Vol 13 (4) ◽  
pp. 10157-10192 ◽  
Author(s):  
E. L. Yates ◽  
L. T. Iraci ◽  
M. C. Roby ◽  
R. B. Pierce ◽  
M. S. Johnson ◽  
...  
Keyword(s):  
Air Quality ◽  
Free Troposphere ◽  
Air Mass ◽  
Air Masses ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Stratospheric Intrusion ◽  
Tropospheric O3 ◽  
Carbon Dioxide Co2 ◽  
The Impact

Abstract. Stratosphere-to-troposphere transport (STT) results in air masses of stratospheric origin intruding into the free troposphere. Once in the free troposphere, O3-rich stratospheric air can be transported and mixed with tropospheric air masses, contributing to the tropospheric O3 budget. Evidence of STT can be identified based on the differences in the trace gas composition of the two regions. Because ozone (O3) is present in such large quantities in the stratosphere compared to the troposphere, it is frequently used as a tracer for STT events. This work reports on airborne in situ measurements of O3 and other trace gases during two STT events observed over California, USA. The first, on 14 May 2012, was associated with a cut-off low, and the second, on 5 June 2012, occurred during a post-trough, building ridge event. In each STT event, airborne measurements identified high O3 within a stratospheric intrusion which was observed as low as 3 km above sea level. During both events the stratospheric air mass was characterized by elevated O3 mixing ratios and reduced carbon dioxide (CO2) and water vapor. The reproducible observation of reduced CO2 within the stratospheric air mass supports the use of non-conventional tracers as an additional method for detecting STT. A detailed meteorological analysis of each STT event is presented and observations are interpreted with the Realtime Air Quality Modeling System (RAQMS). The implications of the two STT events are discussed in terms of the impact on the total tropospheric O3 budget and the impact on air quality and policy-making.

scholarly journals Airborne observations and modeling of springtime stratosphere-to-troposphere transport over California

2013 ◽  
Vol 13 (24) ◽  
pp. 12481-12494 ◽  
Author(s):  
E. L. Yates ◽  
L. T. Iraci ◽  
M. C. Roby ◽  
R. B. Pierce ◽  
M. S. Johnson ◽  
...  
Keyword(s):  
Air Quality ◽  
Free Troposphere ◽  
Air Mass ◽  
Air Masses ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Stratospheric Intrusion ◽  
Tropospheric O3 ◽  
Carbon Dioxide Co2 ◽  
The Impact

Abstract. Stratosphere-to-troposphere transport (STT) results in air masses of stratospheric origin intruding into the free troposphere. Once in the free troposphere, ozone (O3)-rich stratospheric air can be transported and mixed with tropospheric air masses, contributing to the tropospheric O3 budget. Evidence of STT can be identified based on the differences in the trace gas composition of the two regions. Because O3 is present in such large quantities in the stratosphere compared to the troposphere, it is frequently used as a tracer for STT events. This work reports on airborne in situ measurements of O3 and other trace gases during two STT events observed over California, USA. The first, on 14 May 2012, was associated with a cutoff low, and the second, on 5 June 2012, occurred during a post-trough, building ridge event. In each STT event, airborne measurements identified high O3 within the stratospheric intrusion, which were observed as low as 3 km above sea level. During both events the stratospheric air mass was characterized by elevated O3 mixing ratios and reduced carbon dioxide (CO2) and water vapor. The reproducible observation of reduced CO2 within the stratospheric air mass supports the use of non-conventional tracers as an additional method for detecting STT. A detailed meteorological analysis of each STT event is presented, and observations are interpreted with the Realtime Air Quality Modeling System (RAQMS). The implications of the two STT events are discussed in terms of the impact on the total tropospheric O3 budget and the impact on air quality and policy-making.

scholarly journals Production of peroxy nitrates in boreal biomass burning plumes over Canada during the BORTAS campaign

2016 ◽  
Vol 16 (5) ◽  
pp. 3485-3497 ◽  
Author(s):  
Marcella Busilacchio ◽  
Piero Di Carlo ◽  
Eleonora Aruffo ◽  
Fabio Biancofiore ◽  
Cesare Dari Salisburgo ◽  
...  
Keyword(s):  
Boreal Forest ◽  
Forest Fire ◽  
Biomass Burning ◽  
Forest Fires ◽  
Chemical Mechanism ◽  
Fire Emissions ◽  
Fire Plumes ◽  
Peroxy Nitrates ◽  
In Fire ◽  
The Impact

Abstract. The observations collected during the BOReal forest fires on Tropospheric oxidants over the Atlantic using Aircraft and Satellites (BORTAS) campaign in summer 2011 over Canada are analysed to study the impact of forest fire emissions on the formation of ozone (O3) and total peroxy nitrates ∑PNs, ∑ROONO2). The suite of measurements on board the BAe-146 aircraft, deployed in this campaign, allows us to calculate the production of O3 and of  ∑PNs, a long-lived NOx reservoir whose concentration is supposed to be impacted by biomass burning emissions. In fire plumes, profiles of carbon monoxide (CO), which is a well-established tracer of pyrogenic emission, show concentration enhancements that are in strong correspondence with a significant increase of concentrations of ∑PNs, whereas minimal increase of the concentrations of O3 and NO2 is observed. The ∑PN and O3 productions have been calculated using the rate constants of the first- and second-order reactions of volatile organic compound (VOC) oxidation. The ∑PN and O3 productions have also been quantified by 0-D model simulation based on the Master Chemical Mechanism. Both methods show that in fire plumes the average production of ∑PNs and O3 are greater than in the background plumes, but the increase of ∑PN production is more pronounced than the O3 production. The average ∑PN production in fire plumes is from 7 to 12 times greater than in the background, whereas the average O3 production in fire plumes is from 2 to 5 times greater than in the background. These results suggest that, at least for boreal forest fires and for the measurements recorded during the BORTAS campaign, fire emissions impact both the oxidized NOy and O3,  but (1 ∑PN production is amplified significantly more than O3 production and (2) in the forest fire plumes the ratio between the O3 production and the ∑PN production is lower than the ratio evaluated in the background air masses, thus confirming that the role played by the ∑PNs produced during biomass burning is significant in the O3 budget. The implication of these observations is that fire emissions in some cases, for example boreal forest fires and in the conditions reported here, may influence more long-lived precursors of O3 than short-lived pollutants, which in turn can be transported and eventually diluted in a wide area.

scholarly journals Black carbon physical properties and mixing state in the European megacity Paris

2013 ◽  
Vol 13 (11) ◽  
pp. 5831-5856 ◽  
Author(s):  
M. Laborde ◽  
M. Crippa ◽  
T. Tritscher ◽  
Z. Jurányi ◽  
P. F. Decarlo ◽  
...  
Keyword(s):  
Size Distribution ◽  
Biomass Burning ◽  
Coating Thickness ◽  
Traffic Emissions ◽  
Core Mass ◽  
Air Mass ◽  
Air Masses ◽  
Mass Size ◽  
A Minor ◽  
Wet Removal

Abstract. Aerosol hygroscopicity and refractory black carbon (rBC) properties were characterised during wintertime at a suburban site in Paris, one of the biggest European cities. Hygroscopic growth factor (GF) frequency distributions, characterised by distinct modes of more-hygroscopic background aerosol and non- or slightly hygroscopic aerosol of local (or regional) origin, revealed an increase of the relative contribution of the local sources compared to the background aerosol with decreasing particle size. BC-containing particles in Paris were mainly originating from fresh traffic emissions, whereas biomass burning only gave a minor contribution. The mass size distribution of the rBC cores peaked on average at an rBC core mass equivalent diameter of DMEV ~ 150 nm. The BC-containing particles were moderately coated (coating thickness Δcoat ~ 33 nm on average for rBC cores with DMEV = 180–280 nm) and an average mass absorption coefficient (MAC) of ~ 8.6 m2 g−1 at the wavelength λ = 880 nm was observed. Different time periods were selected to investigate the properties of BC-containing particles as a function of source and air mass type. The traffic emissions were found to be non-hygroscopic (GF ≈ 1.0), and essentially all particles with a dry mobility diameter (D0) larger than D0 = 110 nm contained an rBC core. rBC from traffic emissions was further observed to be uncoated within experimental uncertainty (Δcoat ~ 2 nm ± 10 nm), to have the smallest BC core sizes (maximum of the rBC core mass size distribution at DMEV ~ 100 nm) and to have the smallest MAC (~ 7.3 m2g−1 at λ = 880 nm). The biomass burning aerosol was slightly more hygroscopic than the traffic emissions (with a distinct slightly-hygroscopic mode peaking at GF ≈ 1.1–1.2). Furthermore, only a minor fraction (&amp;leq; 10%) of the slightly-hygroscopic particles with 1.1 &amp;leq; GF &amp;leq; 1.2 (and D0 = 265 nm) contained a detectable rBC core. The BC-containing particles from biomass burning were found to have a medium coating thickness as well as slightly larger mean rBC core sizes and MAC values compared to traffic emissions. The aerosol observed under the influence of aged air masses and air masses from Eastern Continental Europe was dominated by a~more-hygroscopic mode peaking at GF ≈ 1.6. Most particles (95%), in the more-hygroscopic mode at D0 = 265 nm, did not contain a detectable rBC core. A significant fraction of the BC-containing particles had a substantial coating with non-refractory aerosol components. MAC values of ~ 8.8 m2g−1 and ~ 8.3 m2g−1 at λ = 880 nm and mass mean rBC core diameters of 150 nm and 200 nm were observed for the aged and continental air mass types, respectively. The reason for the larger rBC core sizes compared to the fresh emissions – transport effects or a different rBC source – remains unclear. The dominant fraction of the BC-containing particles was found to have no or very little coating with non-refractory matter. The lack of coatings is consistent with the observation that the BC-containing particles are non- or slightly-hygroscopic, which makes them poor cloud condensation nuclei. It can therefore be expected that wet removal through nucleation scavenging is inefficient for fresh BC-containing particles in urban plumes. The mixing-state-specific cloud droplet activation behaviour of BC-containing particles including the effects of atmospheric aging processes should be considered in global simulations of atmospheric BC, as the wet removal efficiency remains a major source of uncertainty in its life-cycle.

scholarly journals Water vapor increase in the lower stratosphere of the Northern Hemisphere due to the Asian monsoon anticyclone observed during the TACTS/ESMVal campaigns

2018 ◽  
Vol 18 (4) ◽  
pp. 2973-2983 ◽  
Author(s):  
Christian Rolf ◽  
Bärbel Vogel ◽  
Peter Hoor ◽  
Armin Afchine ◽  
Gebhard Günther ◽  
...  
Keyword(s):  
Water Vapor ◽  
Northern Hemisphere ◽  
Asian Monsoon ◽  
Eastern China ◽  
Potential Temperature ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Air Mass ◽  
Air Masses ◽  
The Impact

Abstract. The impact of air masses originating in Asia and influenced by the Asian monsoon anticyclone on the Northern Hemisphere stratosphere is investigated based on in situ measurements. A statistically significant increase in water vapor (H2O) of about 0.5 ppmv (11 %) and methane (CH4) of up to 20 ppbv (1.2 %) in the extratropical stratosphere above a potential temperature of 380 K was detected between August and September 2012 during the HALO aircraft missions Transport and Composition in the UT/LMS (TACTS) and Earth System Model Validation (ESMVal). We investigate the origin of the increased water vapor and methane using the three-dimensional Chemical Lagrangian Model of the Stratosphere (CLaMS). We assign the source of the moist air masses in the Asian region (northern and southern India, eastern China, southeast Asia, and the tropical Pacific) based on tracers of air mass origin used in CLaMS. The water vapor increase is correlated with an increase of the simulated Asian monsoon air mass contribution from about 10 % in August to about 20 % in September, which corresponds to a doubling of the influence from the Asian monsoon region. Additionally, back trajectories starting at the aircraft flight paths are used to differentiate transport from the Asian monsoon anticyclone and other source regions by calculating the Lagrangian cold point (LCP). The geographic location of the LCPs, which indicates the region where the set point of water vapor mixing ratio along these trajectories occurs, can be predominantly attributed to the Asian monsoon region.

Air mass characterization based on VOC measurements downstream of European and Asian Major Population Centers (MPC) during the research aircraft campaign EMeRGe (2017/2018)

2020 ◽  
Author(s):  
Eric Förster ◽  
Harald Bönisch ◽  
Marco Neumaier ◽  
Florian Obersteiner ◽  
Michael Lichtenstern ◽  
...  
Keyword(s):  
Mainland China ◽  
Anthropogenic Pollution ◽  
Proton Transfer Reaction ◽  
Back Trajectories ◽  
Air Masses ◽  
Airborne Measurements ◽  
Po Valley ◽  
Research Aircraft ◽  
The Impact ◽  
Pollution Plumes

&lt;p&gt;EMeRGe (Effect of Megacities on the Transport and Transformation of Pollutants on the Regional to Global Scales) aims to investigate the impact of MPC emissions on air pollution and chemical processing at local, regional and hemispheric scales by making dedicated airborne measurements using the German research aircraft HALO. Transects and vertical profiling for diverse MPCs (e.g. Rome, London, Taipei, Manila) were performed to determine the composition and transformation of various pollution plumes in Europe and Asia.&lt;/p&gt;&lt;p&gt;To characterize air masses we evaluate different volatile organic compounds (VOCs), measured by a Proton-Transfer-Reaction Mass Spectrometer (PTR-MS), with different or similar sources and different lifetimes. We use the specific tracer acetonitrile to identify air masses influenced by biomass burning (BB), the aromatic compound benzene to tag anthropogenic pollution plumes (e.g. from traffic or industry) and short-lived isoprene as indicator for fresh biogenic influences. Back trajectories based on FLEXTRA (FLEXible TRAjectory model) are used to determine potential source regions of BB affected air and anthropogenic pollution plumes.&lt;/p&gt;&lt;p&gt;Results show that in Europe only minor BB influenced air masses were sampled. However, in Southern France fresh BB close to the source was detected. In contrast to Europe, numerous plumes affected by BB were identified in Asia originating mostly from Southeast Asia.&lt;/p&gt;&lt;p&gt;Air masses with enhanced concentrations in benzene and low concentrations in acetonitrile, indicating anthropogenic pollution, were sampled in Europe over the Po-Valley, Rome, Barcelona and the English Channel. In Asia, plumes were identified along the west coast of Taiwan, the East China Sea and Manila originating from local sources as well as transported from Mainland China.&lt;/p&gt;&lt;p&gt;Significant fresh biogenic influence was found in Europe, as the measurements were performed mostly in summer over land in contrast to Asia were just a minor influence was detected.&lt;/p&gt;

scholarly journals Structure Function Analysis of Water Vapor Simulated with a Convection-Permitting Model and Comparison to Airborne Lidar Observations

2017 ◽  
Vol 74 (4) ◽  
pp. 1201-1210
Author(s):  
Tobias Selz ◽  
Lucas Fischer ◽  
George C. Craig
Keyword(s):  
Water Vapor ◽  
Structure Function ◽  
Airborne Lidar ◽  
Sensitivity Analyses ◽  
Small Scale ◽  
Limited Area ◽  
Air Mass ◽  
Scaling Properties ◽  
Air Masses ◽  
The Impact

Abstract The spatial scale dependence of midlatitude water vapor variability in the high-resolution limited-area model COSMO is evaluated using diagnostics of scaling behavior. Past analysis of airborne lidar measurements showed that structure function scaling exponents depend on the corresponding airmass characteristics, and that a classification of the troposphere into convective and nonconvective layers led to significantly different power-law behaviors for each of these two regimes. In particular, scaling properties in the convective air mass were characterized by rough and highly intermittent data series, whereas the nonconvective regime was dominated by smoother structures with weaker small-scale variability. This study finds similar results in a model simulation with an even more pronounced distinction between the two air masses. Quantitative scaling diagnostics agree well with measurements in the nonconvective air mass, whereas in the convective air mass the simulation shows a much higher intermittency. Sensitivity analyses were performed using the model data to assess the impact of limitations of the observational dataset, which indicate that analyses of lidar data most likely underestimated the intermittency in convective air masses due to the small samples from single flight tracks, which led to a bias when data with poor fits were rejected. Though the quantitative estimation of intermittency remains uncertain for convective air masses, the ability of the model to capture the dominant weather regime dependence of water vapor scaling properties is encouraging.

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