scholarly journals Seasonal variability of measured Ozone production efficiencies in the lower free troposphere of Central Europe

2006 ◽  
Vol 6 (5) ◽  
pp. 9315-9349 ◽  
Author(s):  
P. Zanis ◽  
A. Ganser ◽  
C. Zellweger ◽  
S. Henne ◽  
M. Steinbacher ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Central Europe ◽  
Seasonal Variability ◽  
Transition Period ◽  
Ozone Production ◽  
Data Series ◽  
Research Station ◽  
Monthly Means ◽  
Free Troposphere ◽  
Production Efficiencies

Abstract. In this study we present the seasonal variability of ozone production efficiencies (EN), defined as the net number of ozone molecules produced per molecule of nitrogen oxides (nitrogen oxide (NO) + nitrogen dioxide (NO2)=NOx) oxidized to NOz (total reactive nitrogen (NOy)-NOx) for a seven-year period (1998–2004) at the Swiss high-alpine research station Jungfraujoch (JFJ), 3580 m a.s.l. This dataset is a unique long-term data series of nitrogen levels in the free troposphere over Central Europe and hence it offers an excellent opportunity to perform such an analysis and provide further evidence to the photochemical origin of the ozone spring maximum at locations of the northern hemisphere distant from nearby pollution sources. Experimentally derived daily EN values have been selected for 571 days out of the 2557 days from 1998 to 2004, from which an average ozone production efficiency of 18.8±1.3 molecules of O3 produced per molecule of NOx oxidized was calculated. This value indicates the great potential and importance of photochemical ozone production in the free troposphere. The monthly means of experimentally derived daily EN values show a seasonal variation with lower values from May to August, which can be probably attributed to more efficient vertical transport of polluted air masses from the atmospheric boundary layer up to JFJ. In agreement, theoretically derived monthly EN values show similar seasonal variation. The ratio NOy/CO, a parameter to assess the aging process that has occurred in an air parcel, was used as a criterion to disaggregate the 571 selected days between undisturbed and disturbed free tropospheric (FT). The monthly means of experimentally derived EN values for the undisturbed FT conditions show a distinct seasonal cycle with higher values in the cold season from November to April. The EN values for undisturbed FT conditions are particularly higher than the respective monthly EN values for disturbed FT conditions from February to October. It should be noted that the monthly EN values of March (EN=35.8) and April (EN=34.9) are among the highest values throughout the year for undisturbed FT conditions at JFJ. These results highlight the key and possibly the dominant role for photochemistry in the observed build-up of tropospheric ozone in the winter-spring transition period.

scholarly journals Seasonal variability of measured ozone production efficiencies in the lower free troposphere of Central Europe

2007 ◽  
Vol 7 (1) ◽  
pp. 223-236 ◽  
Author(s):  
P. Zanis ◽  
A. Ganser ◽  
C. Zellweger ◽  
S. Henne ◽  
M. Steinbacher ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Central Europe ◽  
Seasonal Variability ◽  
Transition Period ◽  
Ozone Production ◽  
Data Series ◽  
Research Station ◽  
Monthly Means ◽  
Free Troposphere ◽  
Production Efficiencies

Abstract. In this study we present the seasonal variability of ozone production efficiencies (EN), defined as the net number of ozone molecules produced per molecule of nitrogen oxides (nitrogen oxide (NO) + nitrogen dioxide (NO2)=NOx) oxidized to NOz (total reactive nitrogen (NOy)–NOx) determined from field measurements of a seven-year period (1998–2004) at the Swiss high-alpine research station Jungfraujoch (JFJ), 3580 m a.s.l. This dataset is a unique long-term data series of nitrogen levels in the free troposphere over Central Europe and hence it offers an excellent opportunity to perform such an analysis and provide further evidence to the photochemical origin of the ozone spring maximum at locations of the northern hemisphere distant from nearby pollution sources. Experimentally derived daily EN values have been selected for 571 days out of the 2557 days from 1998 to 2004, from which an average ozone production efficiency of 18.8±1.3 molecules of O3 produced per molecule of NOx oxidized was calculated. This value indicates the great potential and importance of photochemical ozone production in the free troposphere. The monthly means of experimentally derived daily EN values show a seasonal variation with lower values from May to August, which can be probably attributed to more efficient vertical transport of polluted air masses from the atmospheric boundary layer up to JFJ. In agreement, theoretically derived monthly EN values show similar seasonal variation. The ratio NOy/CO, a parameter to assess the aging process that has occurred in an air parcel, was used as a criterion to disaggregate the 571 selected days between undisturbed and disturbed free tropospheric (FT). The monthly means of experimentally derived EN values for the undisturbed FT conditions show a distinct seasonal cycle with higher values in the cold season from November to April. The EN values for undisturbed FT conditions are particularly higher than the respective monthly EN values for disturbed FT conditions from February to October. It should be noted that the monthly EN values of March (EN=35.8) and April (EN=34.9) are among the highest values throughout the year for undisturbed FT conditions at JFJ. These results highlight the key and possibly the dominant role for photochemistry in the observed build-up of tropospheric ozone in the winter-spring transition period.

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 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.

Oxidized nitrogen and ozone production efficiencies in the springtime free troposphere over the Alps

2000 ◽  
Vol 105 (D11) ◽  
pp. 14547-14559 ◽  
Author(s):  
L. J. Carpenter ◽  
T. J. Green ◽  
G. P. Mills ◽  
S. Bauguitte ◽  
S. A. Penkett ◽  
...  
Keyword(s):  
Ozone Production ◽  
Free Troposphere ◽  
The Alps ◽  
Production Efficiencies

scholarly journals Observations of the diurnal and seasonal trends in nitrogen oxides in the western Sierra Nevada

2006 ◽  
Vol 6 (3) ◽  
pp. 4415-4464 ◽  
Author(s):  
J. G. Murphy ◽  
D. A. Day ◽  
P. A. Cleary ◽  
P. J. Wooldridge ◽  
R. C. Cohen
Keyword(s):  
Nitrogen Oxides ◽  
Sierra Nevada ◽  
Thermal Dissociation ◽  
Ozone Production ◽  
Organic Nitrates ◽  
Research Station ◽  
Small Contribution ◽  
Free Troposphere ◽  
Alkyl Nitrates ◽  
Peroxy Nitrates

Abstract. Observations of speciated nitrogen oxides, namely NO2, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), and HNO3 by thermal dissociation laser induced fluorescence (TD-LIF), and supporting chemical and meteorological measurements at Big Hill (1860 m), a high elevation site in California's Sierra Nevada Mountains, are described. From May through October, terrain-driven winds in the region routinely bring air from Sacramento, 100 km southwest of the site, upslope over oak and pine forests to Big Hill during the day, while at night, the site often samples clean, dry air characteristic of the free troposphere. Winter differs mainly in that the meteorology does not favour the buildup of Sacramento's pollution over the Sierra Nevada range, and the urban-influenced air that is seen has been less affected by biogenic VOC emissions, resulting in longer lifetime for NO2 and a predominance of the inorganic forms of nitrogen oxides. Summertime observations at Big Hill can be compared with those from Granite Bay, a Sacramento suburb, and from the University of California's Blodgett Forest Research Station to examine the evolution of nitrogen oxides and ozone within the urban plume. Nitrogen oxide radicals (NO and NO2), which dominate total nitrogen oxides (NOy) at Granite Bay, are rapidly converted into HNO3, ΣPNs, and ΣANs, such that these compounds contribute 29, 30, and 21% respectively to the NOy budget in the plume at Big Hill. Nevertheless, the decreasing concentrations of NO2 as the plume is advected to Big Hill lead to decreases in the production rate of HNO3 and ozone. The data also demonstrate the role that temperature plays in sequestering NO2 into peroxy nitrates, effectively decreasing the rate of ozone production. The important contribution of ΣANs to NOy in the region suggests that they should be considered with regards to export of NOy from the boundary layer. Nocturnal observations of airmasses characteristic of the free troposphere showed lower NOy concentrations, which were dominated by HNO3 with a relatively small contribution from the organic nitrates.

scholarly journals Observations of the diurnal and seasonal trends in nitrogen oxides in the western Sierra Nevada

2006 ◽  
Vol 6 (12) ◽  
pp. 5321-5338 ◽  
Author(s):  
J. G. Murphy ◽  
D. A. Day ◽  
P. A. Cleary ◽  
P. J. Wooldridge ◽  
R. C. Cohen
Keyword(s):  
Nitrogen Oxides ◽  
Sierra Nevada ◽  
Thermal Dissociation ◽  
Ozone Production ◽  
Organic Nitrates ◽  
Research Station ◽  
Small Contribution ◽  
Free Troposphere ◽  
Alkyl Nitrates ◽  
Peroxy Nitrates

Abstract. Observations of speciated nitrogen oxides, namely NO2, total peroxy nitrates (ΣPNs), total alkyl nitrates (ΣANs), and HNO3 by thermal dissociation laser induced fluorescence (TD-LIF), and supporting chemical and meteorological measurements at Big Hill (1860 m), a high elevation site in California's Sierra Nevada Mountains, are described. From May through October, terrain-driven winds in the region routinely bring air from Sacramento, 100 km southwest of the site, upslope over oak and pine forests to Big Hill during the day, while at night, the site often samples clean, dry air characteristic of the free troposphere. Winter differs mainly in that the meteorology does not favour the buildup of Sacramento's pollution over the Sierra Nevada range, and the urban-influenced air that is seen has been less affected by biogenic VOC emissions, resulting in longer lifetime for NO2 and a predominance of the inorganic forms of nitrogen oxides. Summertime observations at Big Hill can be compared with those from Granite Bay, a Sacramento suburb, and from the University of California's Blodgett Forest Research Station to examine the evolution of nitrogen oxides and ozone within the urban plume. Nitrogen oxide radicals (NO and NO2), which dominate total nitrogen oxides (NOy) at Granite Bay, are rapidly converted into HNO3, ΣPNs, and ΣANs, such that these compounds contribute 29, 30, and 21% respectively to the NOy budget in the plume at Big Hill. Nevertheless, the decreasing concentrations of NO2 as the plume is advected to Big Hill lead to decreases in the production rate of HNO3 and ozone. The data also demonstrate the role that temperature plays in sequestering NO2 into peroxy nitrates, effectively decreasing the rate of ozone production. The important contribution of ΣANs to NOy in the region suggests that they should be considered with regards to export of NOy from the boundary layer. Nocturnal observations of airmasses characteristic of the free troposphere showed lower NOy concentrations, which were dominated by HNO3 with a relatively small contribution from the organic nitrates.

Seasonal Variability in Middepth Gyral Circulation Patterns in the Central East/Japan Sea as Revealed by Long-Term Argo Data

2016 ◽  
Vol 46 (3) ◽  
pp. 937-946 ◽  
Author(s):  
Sok Kuh Kang ◽  
Young Ho Seung ◽  
Jong Jin Park ◽  
Jae-Hun Park ◽  
Jae Hak Lee ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Seasonal Variability ◽  
Japan Sea ◽  
Circulation Pattern ◽  
Japan Basin ◽  
Wind Stress Curl ◽  
Argo Data ◽  
Circulating Water ◽  
Significant Seasonal Variation ◽  
Water Columns

AbstractTrajectories of Argo floats deployed in the East/Japan Sea from 2001 to 2014 reveal that the middepth gyral circulation pattern of the Japan basin, the central part of the East/Japan Sea, undergoes a seasonal variation. The middepth circulation of the Japan basin is found to be characterized usually by the gyres trapped to the east of the Bogorov Rise (E-gyres) and those extending farther westward into the whole basin (BW-gyres). The E-gyre trajectories are generally associated with the turning of the floats toward deeper regions off the isobaths. This occurs in winter either on the northern or eastern side of the eastern Japan basin. It seems that the upstream part of the otherwise BW-gyre is subject to a strong negative wind stress curl in winter, and there the circulating water columns are driven toward the deeper region, thus triggering the formation of the E-gyre. The topographic effect associated with the Bogorov Rise seems to interfere thereafter in the process of determining the passage of the E-gyre. Otherwise, the water columns continue to flow along the isobaths, hence maintaining the BW-gyre. To the knowledge of the authors, this is the first observational evidence of seasonal variability in the middepth gyral circulation pattern in the East/Japan Sea. It suggests that oceanic middepth circulation, usually known to be quasi steady or slowly varying on climatological time scales, might also undergo a significant seasonal variation as it does in the East/Japan Sea.

scholarly journals The influence of temperature on ozone production under varying NO<sub><i>x</i></sub> conditions – a modelling study

2016 ◽  
Vol 16 (18) ◽  
pp. 11601-11615 ◽  
Author(s):  
Jane Coates ◽  
Kathleen A. Mar ◽  
Narendra Ojha ◽  
Tim M. Butler
Keyword(s):  
Central Europe ◽  
Surface Ozone ◽  
Reaction Rates ◽  
Air Pollutant ◽  
Box Model ◽  
Chemical Mechanism ◽  
Ozone Production ◽  
Nox Emissions ◽  
Model Simulations ◽  
Rate Of Increase

Abstract. Surface ozone is a secondary air pollutant produced during the atmospheric photochemical degradation of emitted volatile organic compounds (VOCs) in the presence of sunlight and nitrogen oxides (NOx). Temperature directly influences ozone production through speeding up the rates of chemical reactions and increasing the emissions of VOCs, such as isoprene, from vegetation. In this study, we used an idealised box model with different chemical mechanisms (Master Chemical Mechanism, MCMv3.2; Common Representative Intermediates, CRIv2; Model for OZone and Related Chemical Tracers, MOZART-4; Regional Acid Deposition Model, RADM2; Carbon Bond Mechanism, CB05) to examine the non-linear relationship between ozone, NOx and temperature, and we compared this to previous observational studies. Under high-NOx conditions, an increase in ozone from 20 to 40 °C of up to 20 ppbv was due to faster reaction rates, while increased isoprene emissions added up to a further 11 ppbv of ozone. The largest inter-mechanism differences were obtained at high temperatures and high-NOx emissions. CB05 and RADM2 simulated more NOx-sensitive chemistry than MCMv3.2, CRIv2 and MOZART-4, which could lead to different mitigation strategies being proposed depending on the chemical mechanism. The increased oxidation rate of emitted VOC with temperature controlled the rate of Ox production; the net influence of peroxy nitrates increased net Ox production per molecule of emitted VOC oxidised. The rate of increase in ozone mixing ratios with temperature from our box model simulations was about half the rate of increase in ozone with temperature observed over central Europe or simulated by a regional chemistry transport model. Modifying the box model set-up to approximate stagnant meteorological conditions increased the rate of increase of ozone with temperature as the accumulation of oxidants enhanced ozone production through the increased production of peroxy radicals from the secondary degradation of emitted VOCs. The box model simulations approximating stagnant conditions and the maximal ozone production chemical regime reproduced the 2 ppbv increase in ozone per degree Celsius from the observational and regional model data over central Europe. The simulated ozone–temperature relationship was more sensitive to mixing than the choice of chemical mechanism. Our analysis suggests that reductions in NOx emissions would be required to offset the additional ozone production due to an increase in temperature in the future.

89. Seasonal Variation of the Percentage Butterfat Content of Milk. An Examination of the Results of Certain Individual Cow Tests

1935 ◽  
Vol 6 (1) ◽  
pp. 1-5 ◽  
Author(s):  
C. D. Oxley
Keyword(s):  
Seasonal Variation ◽  
Standard Deviation ◽  
Seasonal Variability ◽  
Milk Samples ◽  
Sources Of Error ◽  
The Mean ◽  
Morning Milk

Figures showing the means and the standard deviation of butterfat percentage of milk samples, at the afternoon and morning milkings res-pectively, during the four quarters of the year are presented.The probable sources of error due to the nature of the sample are discussed and the seasonal variability of mean and of standard deviation is considered.The likelihood of the mean of afternoon or of morning milk failing to reach certain specified minima during the respective seasons is calculated.

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