-
F. Freutel,
J. Schneider,
F. Drewnick,
S.-L. von der Weiden-Reinmüller,
M. Crippa,
A. S. H. Prévôt,
U. Baltensperger,
L. Poulain,
A. Wiedensohler,
J. Sciare, [......], A. Stohl,
V. Gros,
A. Colomb,
V. Michoud,
J. F. Doussin,
A. Borbon,
M. Haeffelin,
Y. Morille,
M. Beekmann,
S. Borrmann
[show abstract]
[hide abstract]
ABSTRACT: During July 2009, a one-month measurement campaign was performed in the megacity of Paris. Amongst other measurement platforms, three stationary sites distributed over an area of 40 km in diameter in the greater Paris region enabled a detailed characterization of the aerosol particle and gas phase. Simulation results from the FLEXPART dispersion model were used to distinguish between different types of air masses sampled. It was found that the origin of air masses had a large influence on measured mass concentrations of the secondary species particulate sulphate, nitrate, ammonium, and oxygenated organic aerosol measured with the Aerodyne aerosol mass spectrometer in the submicron particle size range: particularly high concentrations of these species (about 4 μg m−3, 2 μg m−3, 2 μg m−3, and 7 μg m−3, respectively) were measured when aged material was advected from continental Europe, while for air masses originating from the Atlantic, much lower mass concentrations of these species were observed (about 1 μg m−3, 0.2 μg m−3, 0.4 μg m−3, and 1–3 μg m−3, respectively). For the primary emission tracers hydrocarbon-like organic aerosol, black carbon, and NOx it was found that apart from diurnal source strength variations and proximity to emission sources, local meteorology had the largest influence on measured concentrations, with higher wind speeds leading to larger dilution and therefore smaller measured concentrations. Also the shape of particle size distributions was affected by wind speed and air mass origin. Quasi-Lagrangian measurements performed under connected flow conditions between the three stationary sites were used to estimate the influence of the Paris emission plume onto its surroundings, which was found to be rather small. Rough estimates for the impact of the Paris emission plume on the suburban areas can be inferred from these measurements: Volume mixing ratios of 1–14 ppb of NOx, and upper limits for mass concentrations of about 1.5 μg m−3 of black carbon and of about 3 μg m−3 of hydrocarbon-like organic aerosol can be deduced which originate from both, local emissions and the overall Paris emission plume. The secondary aerosol particle phase species were found to be not significantly influenced by the Paris megacity, indicating their regional origin. The submicron aerosol mass concentrations of particulate sulphate, nitrate, and ammonium measured during time periods when air masses were advected from eastern central Europe were found to be similar to what has been found from other measurement campaigns in Paris and south-central France for this type of air mass origin, indicating that the results presented here are also more generally valid.
Atmospheric Chemistry and Physics 01/2013; 13:933-959.
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M Hervo,
B Quennehen,
N I Kristiansen,
J Boulon, A Stohl,
P Fréville,
J -M Pichon,
D Picard,
P Labazuy,
M Gouhier,
J -C Roger,
A Colomb,
A Schwarzenboeck,
K Sellegri
[show abstract]
[hide abstract]
ABSTRACT: During the Eyjafjallajökull eruption (14 April to 24 May 2010), the volcanic aerosol cloud was observed across Europe by several airborne in situ and ground-based remote-sensing instruments. On 18 and 19 May, layers of depolarizing particles (i.e. non-spherical particles) were de-tected in the free troposphere above the Puy de Dôme sta-tion, (PdD, France) with a Rayleigh-Mie LIDAR emitting at a wavelength of 355 nm, with parallel and crossed polar-ization channels. These layers in the free troposphere (FT) were also well captured by simulations with the Lagrangian particle dispersion model FLEXPART, which furthermore showed that the ash was eventually entrained into the plan-etary boundary layer (PBL). Indeed, the ash cloud was then detected and characterized with a comprehensive set of in situ instruments at the Puy de Dôme station (PdD). In agree-ment with the FLEXPART simulation, up to 65 µg m −3 of particle mass and 2.2 ppb of SO 2 were measured at PdD, cor-responding to concentrations higher than the 95 percentile of 2 yr of measurements at PdD. Moreover, the number con-centration of particles increased to 24 000 cm −3 , mainly in the submicronic mode, but a supermicronic mode was also detected with a modal diameter of 2 µm. The resulting op-tical properties of the ash aerosol were characterized by a low scatterin Angström exponent (0.98), showing the pres-ence of supermicronic particles. For the first time to our knowledge, the combination of in situ optical and physi-cal characterization of the volcanic ash allowed the calcu-lation of the mass-to-extinction ratio (η) with no assump-tions on the aerosol density. The mass-to-extinction ra-tio was found to be significantly different from the back-ground boundary layer aerosol (max: 1.57 g m −2 as opposed to 0.33 ± 0.03 g m −2). Using this ratio, ash mass concen-tration in the volcanic plume derived from LIDAR measure-ments was found to be 655 ± 23 µg m −3 when the plume was located in the FT (3000 m above the sea level – a.s.l.). This ratio could also be used to retrieve an aerosol mass concentration of 579 ± 60 µg m −3 on 19 April, when LIDAR observations detected the ash cloud at 3000 m a.s.l. in cor-respondence with model simulations (FLEXPART). On 22 April, another ash plume entered the BL, and although it was more diluted than during the May episode, the French re-search aircraft ATR42 that passed over Clermont-Ferrand in the PBL confirmed the presence of particles with a supermi-cronic mode, again with a modal diameter at 2 µm. This data set combining airborne, ground-based and re-mote sensing observations with dispersion model simulations shows an overall very good coherence during the volcanic eruption period, which allows a good confidence in the char-acteristics of the ash particles that can be derived from this unique data set.
Atmospheric Chemistry and Physics 01/2012; 12(4):1721-1736. · 4.88 Impact Factor
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V Amiridis,
C Zerefos,
S Kazadzis,
E Gerasopoulos,
K Eleftheratos,
M Vrekoussis, A Stohl,
R E Mamouri,
P Kokkalis,
A Papayannis, [......],
C Kontoes,
V Kotroni,
K Lagouvardos,
E Marinou,
E Giannakaki,
E Kostopoulou,
C Giannakopoulos,
A Richter,
J P Burrows,
N Mihalopoulos
[show abstract]
[hide abstract]
ABSTRACT: At the end of August 2009, wild fires ravaged the north-eastern fringes of Athens destroying invaluable forest wealth of the Greek capital. In this work, the impact of these fires on the air quality of Athens and surface radiation levels is examined. Satellite imagery, smoke dispersion modeling and meteorological data confirm the advection of smoke under cloud-free conditions over the city of Athens. Lidar measurements showed that the smoke plume dispersed in the free troposphere and lofted over the city reaching heights between 2 and 4 km. Ground-based sunphotometric measurements showed extreme aerosol optical depth, reaching nearly 6 in the UV wavelength range, accompanied by a reduction up to 70% of solar irradiance at ground. The intensive aerosol optical properties, namely the ångström exponent, the lidar ratio, and the single scattering albedo, showed typical values for highly absorbing fresh smoke particles. In-situ air quality measurements revealed the impact of the smoke plume down to the surface with a slight delay on both the particulate and gaseous phase. Surface aerosols increase was encountered mainly in the fine mode with prominent elevation of OC and EC levels. Photochemical processes, studied via NO x titration of O 3, were also shown to be different compared to typical urban photochemistry. © 2011 Elsevier Ltd.
Atmospheric Environment. 01/2012; 46:536-544.
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A. Merlaud,
M. van Roozendael,
N. Theys,
C. Fayt,
C. Hermans,
B. Quennehen,
A. Schwarzenboeck,
G. Ancellet,
M. Pommier,
J. Pelon,
J. Burkhart, A. Stohl,
M. de Mazière
[show abstract]
[hide abstract]
ABSTRACT: We report airborne differential optical absorption spectroscopy (DOAS)
measurements of aerosol extinction and NO2 tropospheric
profiles performed off the North coast of Norway in April 2008. The DOAS
instrument was installed on the Safire ATR-42 aircraft during the
POLARCAT-France spring campaign and recorded scattered light spectra in
near-limb geometry using a scanning telescope. We use O4
slant column measurements to derive the aerosol extinction at 360 nm.
Regularization is based on the maximum a posteriori solution, for which
we compare a linear and a logarithmic approach. The latter inherently
constrains the solution to positive values and yields aerosol extinction
profiles more consistent with independently measured size distributions.
Two soundings are presented, performed on 8 April 2008 above 71° N,
22° E and on 9 April 2008 above 70° N, 17.8° E. The first
profile shows aerosol extinction and NO2 in the marine
boundary layer with respective values of 0.04±0.005
km-1 and 1.9±0.3 × 109 molec
cm-3. A second extinction layer of 0.01±0.003
km-1 is found at 4 km altitude. During the second sounding,
clouds prevented us to retrieve profile parts under 3 km altitude but a
layer with enhanced extinction (0.025±0.005 km-1) and
NO2 (1.95±0.2 × 109 molec
cm-3) is clearly detected at 4 km altitude. From
CO and ozone in-situ measurements complemented by back-trajectories, we
interpret the measurements in the free troposphere as, for the first
sounding, a mix between stratospheric and polluted air from Northern
Europe and for the second sounding, polluted air from Central Europe
containing NO2. Considering the boundary layer measurements
of the first flight, modeled source regions indicate closer sources,
especially the Kola Peninsula smelters, which can explain the
NO2 enhancement not correlated with a CO increase at the same
altitude.
Atmospheric Chemistry and Physics 04/2011; 11:13525-13574. · 4.88 Impact Factor
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R. Weigel,
S. Borrmann,
J. Kazil,
A. Minikin, A. Stohl,
J. C. Wilson,
J. M. Reeves,
D. Kunkel,
M. de Reus,
W. Frey,
E. R. Lovejoy,
C. M. Volk,
S. Viciani,
F. D'Amato,
F. Cairo,
H. Schlager,
K. S. Law,
G. N. Shur,
G. V. Belyaev,
J. Curtius
[show abstract]
[hide abstract]
ABSTRACT: New particle formation which generates ultrafine aerosol was observed in
the continental tropical Upper Troposphere (UT) and Tropical Tropopause
Layer (TTL), particularly at the bottom of the TTL, by in situ airborne
measurements over South America (January-March, 2005) and West Africa
(August, 2006). Measurements with a set of condensation particle
counters with different dp50 (50% detection efficiency
cut-off particle diameter) were conducted in the altitude range of
12.0-20.5 km on board the high altitude research aircraft M-55
"Geophysica" and at up to 11.5 km altitude on board the research
aircraft DLR Falcon-20. Concentrations of ultrafine particles in the
size range of 6 to 15 nm were derived from these measurements and
several events of new particle formation (NPF) were identified. For two
flight segments (24 February 2005 and 7 August 2006, at 12.5 km
altitude) when recent lifting had influenced the probed air mass, the
concentration of ultrafine particles reached up to 16 000 particles
cm-3 (ambient concentration). A sensitivity study by using an
aerosol model which includes neutral and ion induced nucleation
processes revealed predicted concentrations of ultrafine particles in
reasonable agreement with the in situ observations. NPF over South
America was observed in cloud free air, above thin cirrus, while over
West Africa, in the outflow of a Mesoscale Convective System (MCS),
newly formed particles in the range of several hundred per
cm3 were found to coexist with ice cloud particles as long as
the concentration of cloud particles (dp>2 μm) remained
below 2 cm-3. The occurrence of NPF within the upper
troposphere and the TTL was generally confined within an altitude band
extending from 340 K to 380 K potential temperature, of particular
strength between 350 K and 370 K. By means of a heated aerosol inlet
line (at 250 °C) measurements of particle volatility were performed
which show that within the TTL over South America and West Africa, on
average 10-25% of the particles contained non-volatile cores. In
background UT/TTL conditions the fractions of non-volatile particles
typically ranged up to 50%. Our measurements provide further evidence
for the hypothesis that the tropical UT and the TTL are aerosol source
regions supplying freshly nucleated particles which, if lifted, may
contribute to maintain the stratospheric background aerosol. These
particles can become important for cloud formation in the tropical upper
troposphere, if they further grow such that they can act as cloud
condensation nuclei.
Atmospheric Chemistry and Physics 02/2011; 11:9249-9312. · 4.88 Impact Factor
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A Merlaud,
M Van Roozendael,
N Theys,
C Fayt,
C Hermans,
B Quennehen,
A Schwarzenboeck,
G Ancellet,
M Pommier,
J Pelon,
J Burkhart, A Stohl,
M De Mazière
Atmospheric Chemistry and Physics. 01/2011; 11(17):9219-9236.
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C A Brock,
J Cozic,
R Bahreini,
K D Froyd,
A M Middlebrook,
A McComiskey,
J Brioude,
O R Cooper, A Stohl,
K C Aikin, [......],
J P Schwarz,
H Sodemann,
J R Spackman,
H Stark,
D S Thomson,
T Thornberry,
P Veres,
L A Watts,
C Warneke,
A G Wollny
Atmospheric Chemistry and Physics. 01/2011; 11(6):2423-2453.
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A. Stohl,
A. J. Prata,
S. Eckhardt,
L. Clarisse,
A. Durant,
S. Henne,
N.I. Kristiansen,
Andreas Minikin,
U. Schumann,
P. Seibert,
K. Stebel,
H.E. Thomas,
T. Thorsteinsson,
K. Tørseth,
Bernadett Weinzierl
[show abstract]
[hide abstract]
ABSTRACT: The April–May, 2010 volcanic eruptions of Eyjafjallaj
¨okull, Iceland caused significant economic and social
disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions
of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude
and time. From the inversion, we obtain a total fine
ash emission of the eruption of 8.3±4.2 Tg for particles in the size range of 2.8–28 μm diameter. We evaluate the results of our model results with a posteriori ash emissions using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the “Normal” flying zone in up to 14% (6–16 %), 2% (1–3 %) and 7% (4–11 %), respectively, of the European area. For a limit of 2 mgm−3 only two episodes with fractions of 1.5% (0.2–2.8%) and 0.9% (0.1–1.6%) occurred, while the current “No-Fly” zone criterion of 4 mgm−3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations.
Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.
Atmospheric Chemistry and Physics. 01/2011; 11(2011):4333-4351.
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C. A. Brock,
J. Cozic,
R. Bahreini,
K. D. Froyd,
A. M. Middlebrook,
A. McComiskey,
J. Brioude,
O. R. Cooper, A. Stohl,
K. C. Aikin, [......],
J. P. Schwarz,
H. Sodemann,
J. R. Spackman,
H. Stark,
D. S. Thomson,
T. Thornberry,
P. Veres,
L. A. Watts,
C. Warneke,
A. G. Wollny
[show abstract]
[hide abstract]
ABSTRACT: We present an overview of the background, scientific goals, and
execution of the Aerosol, Radiation, and Cloud Processes affecting
Arctic Climate (ARCPAC) project of April 2008. We then summarize
airborne measurements, made in the troposphere of the Alaskan Arctic, of
aerosol particle size distributions, composition, and optical properties
and discuss the sources and transport of the aerosols. The aerosol data
were grouped into four categories based on gas-phase composition. First,
the background troposphere contained a relatively diffuse, sulfate-rich
aerosol extending from the top of the sea-ice inversion layer to 7.4 km
altitude. Second, a region of depleted (relative to the background)
aerosol was present within the surface inversion layer over sea-ice.
Third, layers of dense, organic-rich smoke from open biomass fires in
Southern Russia and Southeastern Siberia were frequently encountered at
all altitudes from the top of the inversion layer to 7.1 km. Finally,
some aerosol layers were dominated by components originating from fossil
fuel combustion. Of these four categories measured during ARCPAC,
the diffuse background aerosol was most similar to the average
springtime aerosol properties observed at a long-term monitoring site at
Barrow, Alaska. The biomass burning (BB) and fossil fuel layers were
present above the sea-ice inversion layer and did not reach the sea-ice
surface during the course of the ARCPAC measurements. The BB aerosol
layers were highly scattering and were moderately hygroscopic. On
average, the layers produced a noontime net heating of ~0.1 K
day-1 between 2 and 7 km and a~slight cooling at the
surface. The ratios of particle mass to carbon monoxide (CO) in the BB
plumes, which had been transported over distances >5000 km, were
comparable to the high end of literature values derived from previous
measurements in fresh wildfire smoke. These ratios suggest minimal
precipitation scavenging and removal of the BB particles between the
time they were emitted and the time they were observed in dense layers
above the sea-ice inversion layer.
Atmospheric Chemistry and Physics 10/2010; 10:27361-27434. · 4.88 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In order to enhance the process understanding of atmospheric energy
transport into the European Arctic, the magnitude and variability of the
moisture transport from individual cyclones entering the European Arctic
were studied. We applied a moisture source tracking algorithm embedded
in the limited-area numerical weather prediction model (NWP) Climate
High-Resolution Model (CHRM) to trace the evaporation sources and
transport of water vapour from different latitude bands of the North
Atlantic Ocean. Septermber 2002 and December 2006 were chosen as initial
analysis periods, since a particularly large number of cyclones
(including former hurricanes) traveled within the North Atlantic storm
track during these months. The main findings are that moisture from more
southerly source regions is transported at higher altitudes. Stronger
storms draw moisture from a larger area (further south), and the ensuing
precipitation will hence on average originate from further south as
well. Most long-range transport of moisture occurs in the cold frontal
bands. Most moisture that is semi-permanently transferred to north of
60°N in the Atlantic storm track originates from directly south of
that latitude, implying on average short atmospheric moisture lifetimes,
and hence a fast energy turnover.
08/2010; -1:382.
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O R Cooper,
D D Parrish, A Stohl,
M Trainer,
P Nédélec,
V Thouret,
J P Cammas,
S J Oltmans,
B J Johnson,
D Tarasick,
T Leblanc,
I S McDermid,
D Jaffe,
R Gao,
J Stith,
T Ryerson,
K Aikin,
T Campos,
A Weinheimer,
M A Avery
[show abstract]
[hide abstract]
ABSTRACT: In the lowermost layer of the atmosphere-the troposphere-ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases. High concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity. Moreover, tropospheric ozone itself acts as an effective greenhouse gas. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors resulting in widespread increases in ozone concentrations since the late 1800s. At present, east Asia has the fastest-growing ozone precursor emissions. Much of the springtime east Asian pollution is exported eastwards towards western North America. Despite evidence that the exported Asian pollution produces ozone, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995-2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes, with western North America being particularly sensitive to rising Asian emissions. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA's compliance with its ozone air quality standard.
Nature 01/2010; 463(7279):344-8. · 36.28 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We present a new approach for calculating the fraction of very‐short lived substances (VSLS) emitted at the surface (and their degradation products) that reach the stratosphere (β) using the FLEXPART Lagrangian model. The values of β play a key role in determining the efficiency of these compounds for depleting stratospheric ozone, and are used to estimate ozone depletion potentials (ODPs) of several short‐lived compounds. Calculated β and ODPs of VSLSs show large regional and seasonal variability owing to the importance of convective transport. For instance, β and ODPs associated with emissions from the Indian subcontinent is an order of magnitude larger than that from Europe, mid‐latitude North America, or East Asia. The seasonal cycle of β is mainly driven by transport efficiency from the boundary layer into the tropical stratosphere; β has a minimum in winter and a maximum in summer.
Geophysical Research Letters 01/2010; · 3.79 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: 1] The eruption of Kasatochi volcano on 7–8 August 2008 injected material into the troposphere and lower stratosphere of the northern midlatitudes during a period of low stratospheric aerosol background concentrations. Aerosols from the volcanic plume were detected with a lidar in Halifax, Nova Scotia (44.64°N, 63.59°W) 1 week after the eruption and for the next 4 months thereafter. The volcanic origin of the plume is established using the FLEXPART Lagrangian particle transport model for both the stratosphere and troposphere. The stratospheric plume descended 47.1 ± 2.8 m/d on average as it dispersed, corresponding to a cooling rate of 0.60 ± 0.07 K/d. The descent rate was the same for the tropopause (within statistical uncertainties). The top of the plume remained steady at about 18 km altitude and was likely sustained by vertical eddy diffusion from large‐scale horizontal mixing. The lower boundary of the plume descended with the tropopause. The integrated aerosol backscatter between 15 and 19 km altitude was relatively constant at about 8 × 10 −5 sr −1 for 532 nm wavelength. Observations and modeling of Kasatochi aerosols in the middle and lower troposphere indicate a possible ground impact. The volcanic contribution to surface PM 2.5 did not exceed 5 mg/m 3 at the measurement site.
J. Geophys. Res. 01/2010; 115.
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C. Warneke,
K. D. Froyd,
J. Brioude,
R. Bahreini,
C. A. Brock,
J. Cozic,
J.A. de Gouw,
D. W. Fahey,
R. Ferrare,
J. S. Holloway,
A. M. Middlebrook,
L. Miller,
S. Montzka,
J.P. Schwarz,
H. Sodemann,
J.R. Spackman, A Stohl
[show abstract]
[hide abstract]
ABSTRACT: During the ARCPAC (Aerosol, Radiation, and Cloud Processes affecting Arctic Climate) airborne field experiment in April 2008 in northern Alaska, about 50 plumes were encountered with the NOAA WP-3 aircraft between the surface and 6.5 km. Onboard measurements and the transport model FLEXPART showed that most of the plumes were emitted by forest fires in southern Siberia-Lake Baikal area and by agricultural burning in Kazakhstan-southern Russia. Unexpectedly, these biomass burning plumes were the dominant aerosol and gas-phase features encountered in this area during April. The influence on the plumes from sources other than burning was small. The chemical characteristics of plumes from the two source regions were different, with higher enhancements relative to CO for most gas and aerosol species from the agricultural fires. In 2008, the fire season started earlier than usual in Siberia, which may have resulted in unusually efficient transport of biomass burning emissions into the Arctic.
Geophysical Research Letters 11/2009; 37:L01801. · 3.79 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: On many days in polar springtime, a nearly complete removal of ozone
from the polar boundary layer can be observed in widespread parts of
Arctic and Antarctic. Responsible for these so called Ozone Depletion
Events (ODEs) is the catalytic destruction of ozone by halogens. These
can be released from sea salt to the gas phase by heterogeneous
reactions on newly formed sea ice, snow or aerosols. Here, bromine has
been identified as the key halogen in the destruction cycle. It reacts
together with ozone to bromine oxide (BrO), which strengthens the
bromine release and ozone destruction by autocatalytic processes. BrO
can be detected In-Situ or by absorption spectroscopy from the ground or
from satellites and also has a large impact on the deposition of gaseous
mercury in the sensitive polar ecosystem. The exact mechanism, which
leads to an initial bromine release and the influence of transport and
chemical processes on BrO is still not clearly understood. In this
study, BrO measurements of the satellite instrument GOME-2 together with
model calculations of the dispersion model FLEXPART and the chemistry
model MECCA are used to interpret selected BrO events, which could be
observed over many days and large areas to get new information about
source regions of BrO and the influence of transport and chemistry on
the evolution of these events.
03/2009; 11:8754.
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[show abstract]
[hide abstract]
ABSTRACT: 1] The atmospheric observatory at the Norwegian Research Station Troll in Queen Maud Land, Antarctica, holds, since February 2007, the first all-year Antarctic atmospheric aerosol particle number size distribution measurements. These are colocated with measurements of the aerosol absorption and spectral scattering coefficients. In June 2007, this instrument set observed an aerosol whose properties were indicative of a biomass burning aerosol. These properties included two log-normal size distribution modes with median particle diameters of 0.105 mm and 0.36 mm, sharply falling off to smaller and larger sizes, and peaks in scattering and absorption coefficient. With backward plume calculations of the Lagrangian transport model FLEXPART and the MODIS fire activity product, a source-receptor relationship was established between biomass burning events in Central Brazil and the aerosol seen at Troll. This is the first direct evidence that the Antarctic continent is susceptible to emissions from as far north as Southern tropical latitudes.
Geophys. Res. Lett. 01/2009; 36.
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Journal of Geophysical Research 01/2009; 114(D00F07):doi:10.1029/2008JD011604. · 3.02 Impact Factor
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P. S. Monks,
C. Granier,
S. Fuzzi, A. Stohl,
M. L. Williams,
H. Akimoto,
M. Amman,
A. Baklanov,
U. Baltensperger,
I. Bey, [......],
K. Sellegri,
R. Steinbrecher,
D. Simpson,
ten Brink H,
J. Theloke,
van der Werf G.R,
R. Vautard,
V. Vestreng,
Ch. Vlachokostas,
von Glasow R
[show abstract]
[hide abstract]
ABSTRACT: Air quality transcends all scales with in the atmosphere from the local to the global with handovers and feedbacks at each scale interaction. Air quality has manifold effects on health, ecosystems, heritage and climate. In this review the state of scientific understanding in relation to global and regional air quality is outlined. The review discusses air quality, in terms of emissions, processing and transport of trace gases and aerosols. New insights into the characterization of both natural and anthropogenic emissions are reviewed looking at both natural (e.g. dust and lightning) as well as plant emissions. Trends in anthropogenic emissions both by region and globally are discussed as well as biomass burning emissions. In terms of chemical processing the major air quality elements of ozone, non-methane hydrocarbons, nitrogen oxides and aerosols are covered. A number of topics are presented as a way of integrating the process view into the atmospheric context; these include the atmospheric oxidation efficiency, halogen and HOx chemistry, night time chemistry, tropical chemistry, heat waves, megacities, biomass burning and the regional hot spot of the Mediterranean. New findings with respect to the transport of pollutants across the scales are discussed, in particular the move to quantify the impact of long-range transport on regional air quality. Gaps and research questions that remain intractable are identified. The review concludes with a focus of research and policy questions for the coming decade. In particular, the policy challenges for concerted air quality and climate change policy (co-benefit) are discussed.
doi:10.1016/j.atmosenv.2009.08.021.
Atmospheric Environment 01/2009; 43(43):5268-5350. · 3.46 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Volcanic ash is a known hazard to aviation. Currently there are several satellite-based measurements that can detect volcanic substances, notably ash and SO<sub>2</sub> gas, and these have been used in an ad hoc way to provide information to Volcanic Ash Advisory Centres (VAACs) and then to aviation to assist averting danger. While these data have been extremely useful, they lack quantitative value and all the data (except for the recent CALIPSO lidar measurements) lack height information- thought to be critical for aviation. A new project initiated by the European Space Agency (ESA) has been established to support aviation by supplying quantitative and timely satellite-based products and to fill the gaps in knowledge regarding the avoidance of hazardous volcanic clouds. The aims and implementation of the project -¿Support to Aviation for Volcanic Ash Avoidance (SAVAA)¿are described here. The main outcomes of the 3 year project will be the completion of a demonstration system-VAS<sup>3</sup> that will be able to ingest satellite data and meteorological wind fields, compute the injection height profile of volcanic emissions to produce a range of analysis fields (products) that can be swiftly provided to support aviation avoid hazardous volcanic clouds.
Use of Remote Sensing Techniques for Monitoring Volcanoes and Seismogenic Areas, 2008. USEReST 2008. Second Workshop on; 12/2008
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ABSTRACT: Arctic air pollution has received renewed interest recently because of
its contribution to climate change in the Arctic. Nevertheless, its
sources are still not known with sufficient accuracy. Most of our
understanding of Arctic air pollution sources is based on model
simulations, analysis of air pollution episodes or, at best, statistical
analysis of air mass back-trajectories. Here, we present a new approach,
namely combining the output of a Lagrangian particle dispersion model,
FLEXPART, with measurement data from Arctic air pollution monitoring
sites (Alert, Barrow, Summit, Zeppelin). This approach is similar to
existing statistical methods for analyzing back-trajectories in
conjunction with air pollution monitoring data. However, it has the
advantage that the underlying model calculations also take into account
turbulence and convection in the atmosphere, which are ignored by
ordinary trajectory calculations. FLEXPART is run 20 days backward in
time from each of the stations and every three hours, for several years.
With every calculation, a so-called potential emission sensitivity
(PES) field is obtained, which identifies where the measured air mass
has come into contact with the Earth's surface. It quantitatively
measures the sensitivity of the signal obtained at the station, to
emissions occurring at or near the surface. By combining these PES
fields with measured concentrations of several trace species e.g.,
carbon monoxide, sulphate, black carbon, and ozone. By performing a
statistical analysis, we identify where the measured species most likely
originate. Statistical analyses are performed both for average
concentrations as well as the 10th and 90th percentiles of the measured
frequency distribution. We implement a bootstrap resampling procedure to
verify the statistical significance of the patterns observed in our
retrieved PES maps. Some of our findings are: carbon monoxide and
sulphate measured at Zeppelin originate from the Eurasian continent
throughout the year. The statistical analysis even identifies specific
source areas such as Norilsk/Murmansk/Moscow or the Black Sea region as
well as from East Asia. For black carbon measured at Barrow, we also
identify the Eurasian continent as the major source region during
winter. However, during summer the highest black carbon concentrations
arrive from Alaska and are presumably caused by boreal forest fires
there. For ozone measured at Zeppelin, we find that titration by NO
emissions causes the lowest ozone concentration in winter to arrive from
Europe, whereas in summer photochemical ozone formation and transport
from Europe causes the highest ozone concentrations. In spring (and
partly in summer), air with the lowest ozone concentrations arrive from
within the Arctic, likely indicating the importance of ozone depletion
events.
AGU Fall Meeting Abstracts. 11/2008; -1:01.
