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ABSTRACT: This work introduces an index to identify deep stratospheric intrusions (SI) from measurement data alone, without requiring
additional model-based information. This stratospheric intrusion index (SI2) provides a qualitative description of SI event behaviour by summarizing the information from different tracer variations.
Moreover, being independent from any model constraint, the SI2 can also represent a valid tool to help in evaluating the capacity of chemistry-transport and chemistry-climate models in
simulating deep stratosphere to troposphere transport. The in situ variations of ozone, beryllium-7 and relative humidity
were used to calculate the index. The SI2 was applied on 8-year data recorded at the regional GAW station of Mt. Cimone (2165m asl; 44.10N, 10.70E: Italy). The comparison
of the SI2 behaviour with a pre-existing database obtained by also using model products, permitted us to tune a SI2-threshold value capable of identifying SI events efficiently. In good agreement with previous climatological studies across
Europe, at Mt. Cimone, the averaged monthly SI frequency obtained by the SI2 analysis showed a clear seasonal cycle with a winter maximum and a spring-summer minimum. These results suggest that the
presented methodology is efficient for both identifying SI events and evaluating their annual frequency at the considered
baseline measurement site.
Theoretical and Applied Climatology 04/2012; 97(3):317-325. · 1.94 Impact Factor
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ABSTRACT: The work focuses on the analysis of CO2 and O3 surface variations observed during five summer experimental campaigns carried out at the ‘Icaro Camp’ clean air facility (74.7°S, 164.1°E, 41 m a.s.l.) of the ‘Mario Zucchelli’ Italian coastal research station. This experimental activity allowed the definition of summer average background O3 values that ranged from 18.3 ± 4.7 ppbv (summer 2005–2006) to 21.3 ± 4.0 ppbv (summer 2003–2004). Background CO2 concentrations showed an average growth rate of 2.10 ppmv yr–1, with the highest CO2 increase between the summer campaigns 2002–2003 and 2001–2002 (+2.85 ppmv yr–1), probably reflecting the influence of the 2002/2003 ENSO event. A comparison with other Antarctic coastal sites suggested that the summer background CO2 and O3 at MZS-IC are well representative of the average conditions of the Ross Sea coastal regions. As shown by the analysis of local wind direction and by 3-D back-trajectory calculations, the highest CO2 and O3 values were recorded in correspondence to air masses flowing from the interior of the Antarctic continent. These results suggest that air mass transport from the interior of the continent exerts an important influence on air mass composition in Antarctic coastal areas.
Tellus B 09/2011; 63(5):831 - 842. · 4.38 Impact Factor
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S. Decesari,
M. C. Facchini,
C. Carbone,
L. Giulianelli,
M. Rinaldi,
E. Finessi,
S. Fuzzi,
A. Marinoni, P. Cristofanelli,
R. Duchi,
P. Bonasoni,
E. Vuillermoz,
J. Cozic,
J. L. Jaffrezo,
P. Laj
[show abstract]
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ABSTRACT: We report chemical composition data for PM10 and
PM1 from the Nepal Climate Observatory-Pyramid (NCO-P), the
world's highest aerosol observatory, located at 5079 m a.s.l. at the
foothills of Mt. Everest. Despite its high altitude, the average
PM10 mass apportioned by the chemical analyses is of the
order of 6 μg m-3 (i.e., 10 μg/scm), with almost
a half of this mass accounted for by organic matter, elemental carbon
(EC) and inorganic ions, the rest being mineral dust. Organic matter, in
particular, accounted for by 2.0 μg m-3 (i.e., 3.6
μg/scm) on a yearly basis, and it is by far the major PM10
component beside mineral oxides. Non-negligible concentrations of EC
were also observed (0.36 μg/scm), confirming that optically-active
aerosol produced from combustion sources can be efficiently transported
up the altitudes of Himalayan glaciers. The concentrations of
carbonaceous and ionic aerosols follow a common time trend with a
maximum in the premonsoon season, a minimum during the monsoon and a
slow "ramp-up" period in the postmonsoon and dry seasons, which is the
same phenomenology observed for other Nepalese Himalayan sites in
previous studies. Such seasonal cycle can be explained by the seasonal
variations of dry and moist convection and of wet scavenging processes
characterizing the climate of north Indian subcontinent. We document the
effect of orographic transport of carbonaceous and sulphate particles
upslope the Himalayas, showing that the valley breeze circulation, which
is almost permanently active during the out-of-monsoon season, greatly
impacts the chemical composition of PM10 and PM1
in the high Himalayas and provides an efficient mechanism for bringing
anthropogenic optically-active aerosols into the Asian upper troposphere
(>5000 m a.s.l.). The concentrations of mineral dust are impacted to
a smaller extent by valley breezes and follow a unique seasonal cycle
which suggest multiple source areas in central and south-west Asia. Our
findings, based on two years of observations of the aerosol chemical
composition, provide clear evidence that the southern side of the high
Himalayas are impacted by transport of anthropogenic aerosols which
constitute the Asian brown cloud.
Atmospheric Chemistry and Physics 10/2009; 9:25487-25522. · 4.88 Impact Factor
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ABSTRACT: Ozone concentration measurements were made during December from 2001–2005 to quantify the contributions of different processes to near-surface ozone concentrations (O3) in Terra Nova Bay, Antarctica. The average O3 concentration was 20.3 ppbv. On days characterized by high solar radiation fluxes (HSR), significantly higher concentrations of O3 (21.3 ppbv) were recorded compared to days with low solar radiation fluxes (LSR days, 16.8 ppbv). High O3 concentrations could be related to strong winds from SW–NW. Three-dimensional back-trajectories show that air from the interior of the continent could affect O3 at Terra Nova Bay. Moreover, during HSR days, high O3 concentrations were also recorded in connection with weak circulation, suggesting that emissions from the Italian base (located 2 km north) could also represent a significant source of O3. To clarify the role of local pollution in Terra Nova Bay, O3 values were also calculated using the photochemical steady state (PSS) approximation under clear sky and cloudy conditions.
Antarctic Science 07/2008; 20(04):415 - 421. · 1.56 Impact Factor
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P Bonasoni,
P Laj,
F Angelini,
J Arduini,
U Bonafè,
F Calzolari, P Cristofanelli,
S Decesari,
M C Facchini,
S Fuzzi, [......],
A Marinoni,
A Petzold,
F Roccato,
J C Roger,
K Sellegri,
M Sprenger,
H Venzac,
G P Verza,
P Villani,
E Vuillermoz
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ABSTRACT: In this work we present the new ABC-Pyramid Atmospheric Research Observatory (Nepal, 27.95 N, 86.82 E) located in the Himalayas, specifically in the Khumbu valley at 5079 m a.s.l. This measurement station has been set-up with the aim of investigating natural and human-induced environmental changes at different scales (local, regional and global). After an accurate instrumental set-up at ISAC-CNR in Bologna (Italy) in autumn 2005, the ABC-Pyramid Observatory for aerosol (physical, chemical and optical properties) and trace gas measurements (ozone and climate altering halocarbons) was installed in the high Khumbu valley in February 2006. Since March 2006, continuous measurements of aerosol particles (optical and physical properties), ozone (O3) and meteorological parameters as well as weekly samplings of particulate matter (for chemical analyses) and grab air samples for the determination of 27 halocarbons, have been carried out. These measurements provide data on the typical atmospheric composition of the Himalayan area between India and China and make investigations of the principal differences and similarities between the monsoon and pre-monsoon seasons possible. The study is carried out within the framework of the Ev-K2-CNR "SHARE-Asia" (Stations at High Altitude for Research on the Environment in Asia) and UNEP-"ABC" (Atmospheric Brown Clouds) projects. With the name of "Nepal Climate Observatory-Pyramid" the station is now part of the Observatory program of the ABC project.
Science of The Total Environment 04/2008; 391(2-3):252-61. · 3.29 Impact Factor
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ABSTRACT: Particle size distribution in the range 0.3<D(p)<or=20 microm, has been analysed from August 2002 to July 2006 at the GAW Station of Mt. Cimone (44.10 N, 10.42 E; 2165 m asl) in the northern Italian Apennines. The seasonal aerosol number size distribution, characterized by a bimodal shape, showed a behaviour typical for background conditions, characterized by highest values in summer and lowest in winter. The seasonal and diurnal variations of the larger accumulation mode (0.3<D(p)<or=1 microm average values: 26.15 cm(-3)) and the coarse mode (1<Dp<or=20 microm, average value: 0.17 cm(-3)) particle number concentrations (N 0.3-1 and N 1-20, respectively) exhibited a seasonal cycle with the highest values in spring-summer and the lowest value in autumn-winter. Except in winter, N 0.3-1 showed a clear diurnal variation with high values during day-time. N 1-20 showed a less marked diurnal variation (but with higher variability), suggesting the influence of non-continuous sources of coarse particle (i.e. Saharan dust events). Since July 2005, continuous measurement of black carbon (BC) concentrations was also available at the measurement site. On average low BC concentrations were recorded (average value: 0.28 microg m(-3)) even if a few events of high concentrations were recorded both in warm and cold season. Apart from wet scavenging processes which strongly affected aerosol concentrations, combined analysis of N 0.3-1, BC, meteorological parameters and air mass back-trajectories, suggests that the transport of polluted air masses from the lower troposphere (by local, regional or long-range transport) represents an important mechanism favouring N 0.3-1 and BC increases at Mt. Cimone. In particular, a trajectory statistical analysis for the period July 2005-July 2006 allowed the identification of the main source regions of BC and N 0.3-1 for Mt. Cimone: north Italy, west Europe and east Europe.
Science of The Total Environment 03/2008; 391(2-3):241-51. · 3.29 Impact Factor
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ABSTRACT: Its location in the Mediterranean region and its physical characteristics render Mt. Cimone (44 • 11 N, 10 • 42 E), the highest peak of the Italian northern Apennines (2165 m asl), particularly suitable to study the transport of air masses from the north African desert area to Europe. During these northward transports 12 dust events were registered in measurements of the aerosol concentration at the station dur-ing the period June–December 2000, allowing the study of the impact of mineral dust transports on free tropospheric ozone concentrations, which were also measured at Mt. Ci-mone. Three-dimensional backward trajectories were used to determine the air mass origin, while TOMS Aerosol In-dex data for the Mt. Cimone area were used to confirm the presence of absorbing aerosol over the measurement site. A trajectory statistical analysis allowed identifying the main source areas of ozone and aerosols. The analysis of these back trajectories showed that central Europe and north and central Italy are the major pollution source areas for ozone and fine aerosol, whereas the north African desert re-gions were the most important source areas for coarse aerosol and low ozone concentrations. During dust events, the Mt. Cimone mean volume concentration for coarse particles was 6.18 µm 3 /cm 3 compared to 0.63 µm 3 /cm 3 in dust-free con-ditions, while the ozone concentrations were 4% to 21% lower than the monthly mean background values. Our obser-vations show that surface ozone concentrations were lower than the background values in air masses coming from north Africa, and when these air masses were also rich in coarse particles, the lowest ozone values were registered. More-over, preliminary results on the possible impact of the dust events on PM 10 and ozone values measured in Italian urban Correspondence to: P. Bonasoni (p.bonasoni@isac.cnr.it) and rural areas showed that during the greater number of the considered dust events, significant PM 10 increases and ozone decreases have occurred in the Po valley.
Atmospheric Chemistry and Physics 01/2004; 4:1201-1215.
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ABSTRACT: Its location in the Mediterranean region and its physical characteristics render Mt. Cimone (44 • 11 N, 10 • 42 E), the highest peak of the Italian northern Apennines (2165 m asl), particularly suitable to study the transport of air masses from the north African desert area to Europe. During these northward transports 12 dust events were registered in measurements of the aerosol concentration at the station dur-ing the period June–December 2000, allowing the study of the impact of mineral dust transports on free tropospheric ozone concentrations, which were also measured at Mt. Ci-mone. Three-dimensional backward trajectories were used to determine the air mass origin, while TOMS Aerosol In-dex data for the Mt. Cimone area were used to confirm the presence of absorbing aerosol over the measurement site. A trajectory statistical analysis allowed identifying the main source areas of ozone and aerosols. The analysis of these back trajectories showed that central Europe and north and central Italy are the major pollution source areas for ozone and fine aerosol, whereas the north African desert re-gions were the most important source areas for coarse aerosol and low ozone concentrations. During dust events, the Mt. Cimone mean volume concentration for coarse particles was 6.18 µm 3 /cm 3 compared to 0.63 µm 3 /cm 3 in dust-free con-ditions, while the ozone concentrations were 4% to 21% lower than the monthly mean background values. Our obser-vations show that surface ozone concentrations were lower than the background values in air masses coming from north Africa, and when these air masses were also rich in coarse particles, the lowest ozone values were registered. More-over, preliminary results on the possible impact of the dust events on PM 10 and ozone values measured in Italian urban Correspondence to: P. Bonasoni (p.bonasoni@isac.cnr.it) and rural areas showed that during the greater number of the considered dust events, significant PM 10 increases and ozone decreases have occurred in the Po valley.
ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2004; 4:1201-1215. · 5.52 Impact Factor
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A. Stohl,
P. Bonasoni, P. Cristofanelli,
W. Collins,
J. Feichter,
A. Frank,
C. Forster,
E. Gerasopoulos,
H. Gäggeler,
P. James, [......],
G. J. Roelofs,
E. Scheel,
C. Schnabel,
P. Siegmund,
L. Tobler,
T. Trickl,
H. Wernli,
V. Wirth,
P. Zanis,
C. Zerefos
[show abstract]
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ABSTRACT: This paper provides a review of stratosphere-troposphere exchange (STE), with a focus on processes in the extratropics. It also addresses the relevance of STE for tropospheric chemistry, particularly its influence on the oxidative capacity of the troposphere. After summarizing the current state of knowledge, the objectives of the project Influence of Stratosphere-Troposphere Exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity ( STACCATO), recently funded by the European Union, are outlined. Several papers in this Journal of Geophysical Research Atmospheres special section present the results of this project, of which this paper gives an overview. STACCATO developed a new concept of STE in the extratropics, explored the capacities of different types of methods and models to diagnose STE, and identified their various strengths and shortcomings. Extensive measurements were made in central Europe, including the first monitoring over an extended period of time of beryllium-10 ( 10 Be), to provide a suitable database for case studies of stratospheric intrusions and for model validation. Photochemical models were used to examine the impact of STE on tropospheric ozone and the oxidizing capacity of the troposphere. Studies of the present interannual variability of STE and projections into the future were made using reanalysis data and climate models.
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P. Cristofanelli,
P. Bonasoni,
W. Collins,
J. Feichter,
C. Forster,
A. Kentarchos,
P.W. Kubik,
P. James,
C. Land,
J. Meloen,
G. J. Roelofs,
P. Siegmund,
M. Sprenger,
A. Stohl,
H. Wernli,
C. Schnabel,
L. Tobler,
L. Tositti,
T. Trickl,
P. Zanis
[show abstract]
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ABSTRACT: [1] During the EU-project Influence of Stratosphere-Troposphere exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity (STACCATO), a combined approach of a measurement network and numerical simulations was used to estimate the strength and frequency of stratosphere-to-troposphere transport (STT) events and their influence on tropospheric chemistry. Measurements of surface ozone, beryllium-7, and beryllium-10 concentrations and meteorological parameters at four European high mountain stations, as well as atmospheric profiles obtained by ozone soundings and a high-resolution lidar, were carried out. In order to simulate STT events, seven different models have been applied by the STACCATO partners. These are two trajectory models (LAGRANTO and FLEXTRA), a Lagrangian transport model (FLEXPART), a Lagrangian chemistry-transport model (STOCHEM), a Eulerian transport model (TM3), and two general circulation models (ECHAM4 and MA-ECHAM4). In order to investigate the strengths and weaknesses of each of these models and to identify the reasons for their discrepancies, a detailed comparison with measured data is presented in this paper. These models provided fluxes and concentrations of a stratospheric tracer, as well as the vertical profiles of ozone and radionuclides for a stratospheric intrusion case study that occurred over Europe in the year 1996. The comparison of the model results with the measurement data and the satellite observations revealed that all the models captured the general behavior of the event. However, great differences were found in the intensity and spatial development of the simulated intrusion event.
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ABSTRACT: In order to evaluate the background ozone concentration at Mt. Cimone (2165 m a.s.l.), the contribution of air masses characterised by different provenances is analysed in this paper. The analysis method is based on identification of background air masses which travelled above the 780 hPa pressure level for at least 48 h before arriving at Mt. Cimone. Not being recently mixed with boundary layer air, these air masses are characterised by a chemical age greater than 2 days. This analysis has shown that under background conditions the yearly principal maximum of ozone is recorded in spring and a secondary maximum is recorded in summer. In contrast, if we consider non-background conditions, the principal maximum is found in late summer and a secondary one in spring. In addition, the analysis indicates the presence of a smooth latitudinal gradient of background ozone concentrations in air masses arriving at Mt. Cimone, with higher concentrations coming from the north and lower ones from the south.
Atmospheric Environment.
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ABSTRACT: In order to evaluate the possible effects of heatwave phenomena on background O3 concentrations, the average summer O3 concentrations at the high mountain station of Mt. Cimone (MTC—2165 m a.s.l.) have been analyzed. In particular, at this baseline station unusually high O3 concentrations were recorded during August 2003, when an intense heatwave (the “August heatwave”) affected Europe. During this heatwave, the highest O3 concentrations were recorded at MTC in connection with air masses coming from continental Europe and the Po basin boundary layer as shown by three-dimensional air mass back-trajectory and mixing height analyzes. However, high O3 concentrations were also recorded in air masses coming from the middle troposphere (above 3000 m a.s.l.), thus suggesting the presence of O3-rich atmospheric layers over Europe. This could be due to the large extension of the mixing layer which favoured the transport of high concentrations of O3 and its precursors to altitudes that would usually be in the free troposphere. Other than from traffic and industrial activities, a contribution to the high O3 concentrations recorded at MTC during the August heatwave could derive from fires in the North of Italy, as suggested by a well-documented episode and supported by in situ CO2 measurements used as non-conventional tracer for fire emissions.
Atmospheric Environment.
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J. Meloen,
P. Siegmund,
P. van Velthoven,
H. Kelder,
M. Sprenger,
H. Wernli,
A. Kentarchos,
G.J.H. Roelofs,
J. Feichter,
C. Land,
C. Forster,
P. James,
A. Stohl,
W. Collins, P. Cristofanelli
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P. Cristofanelli,
P. Bonasoni,
W. Collins,
J. Feichter,
C. Forster,
P. James,
A. Kentarchos,
P.W. Kubik,
C. Land,
J. Meloen,
G.J.H. Roelofs,
P. Siegmund,
M. Sprenger,
C. Schnabel,
A. Stohl,
L. Tobler,
L. Tositti,
T. Trickl,
P. Zanis
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A. Marinoni, P. Cristofanelli,
P. Laj,
R. Duchi,
F. Calzolari,
S. Decesari,
K. Sellegri,
E. Vuillermoz,
G. P. Verza,
P. Villani,
P. Bonasoni
[show abstract]
[hide abstract]
ABSTRACT: Aerosol mass and the absorbing fraction are important variables, needed to constrain the role of atmospheric particles in the Earth radiation budget, both directly and indirectly through CCN activation. In particular, their monitoring in remote areas and mountain sites is essential for determining source regions, elucidating the mechanisms of long range transport of anthropogenic pollutants, and validating regional and global models. Since March 2006, aerosol mass and black carbon concentration have been monitored at the Nepal Climate Observatory-Pyramid, a permanent high-altitude research station located in the Khumbu valley at 5079 m a.s.l. below Mt. Everest. The first two-year averages of PM1 and PM1‑10 mass were 1.94 μg m‑3 and 1.88 μg m‑3, with standard deviations of 3.90 μg m‑3 and 4.45 μg m‑3, respectively, while the black carbon concentration average is 160.5 ng m‑3, with a standard deviation of 296.1 ng m‑3. Both aerosol mass and black carbon show well defined annual cycles, with a maximum during the pre-monsoon season and a minimum during the monsoon. They also display a typical diurnal cycle during all the seasons, with the lowest particle concentration recorded during the night, and a considerable increase during the afternoon, revealing the major role played by thermal winds in influencing the behaviour of atmospheric compounds over the high Himalayas. The aerosol concentration is subject to high variability: in fact, as well as frequent "background conditions" (55% of the time) when BC concentrations are mainly below 100 ng m‑3, concentrations up to 5 μg m‑3 are reached during some episodes (a few days every year) in the pre-monsoon seasons. The variability of PM and BC is the result of both short-term changes due to thermal wind development in the valley, and long-range transport/synoptic circulation. At NCO-P, higher concentrations of PM1 and BC are mostly associated with regional circulation and westerly air masses from the Middle East, while the strongest contributions of mineral dust arrive from the Middle East and regional circulation, with a special contribution from North Africa and South-West Arabian Peninsula in post-monsoon and winter season.
Atmospheric Chemistry and Physics.
