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PNO y /NO y gas over SA. The ratios are plotted for temperatures and partial pressures within the 25 and 75 percentiles around the respective median values of 226.8 K and 1.37 * 10 À8 hPa, respectively. The 1-s data of the ratio are given along with means and standard deviations. The 1-s values have been averaged over SA intervals of 50 mm 2 /cm 3 .
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The uptake of reactive nitrogen species on ice crystals in cirrus clouds was investigated by simultaneous aircraft-based measurements of gas- and condensed-phase NOy, ice particle size distribution and total aerosol surface area. The measurements were performed in 2000 during the INCA campaign at northern and southern midlatitudes at local autumn....
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A parametric study of the instantaneous
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High resolution mid-infrared limb emission spectra observed by the spaceborne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) showing evidence of cloud interference are analyzed. Using the new line-by-line multiple scattering [Approximate] Spherical Atmospheric Radiative Transfer code (SARTre), a sensitivity study with respect to...
The physical and optical properties of persistent contrails were studied
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Citations
... The above studies focused on trace gases linked to air quality and provided relatively sparse information on GHGs. Long-lived greenhouse gases such as CH 4 and CO 2 emitted from individual European urban areas have been investigated in airborne and ground-based studies, e.g. for London (O'Shea et al., 2014;Helfter et al., 2016;Pitt et al., 2019), Paris (Bréon et al., 2015;Lian et al., 2019), Cracow (Kuc et al., 2003;Zimnoch et al., 2019), Berlin , and Rome (Gioli et al., 2014). Collectively, they report on inconsistencies between the current emission inventories and measurements. ...
Megacities and other major population centres (MPCs) worldwide are
major sources of air pollution, both locally as well as downwind. The
overall assessment and prediction of the impact of MPC pollution on
tropospheric chemistry are challenging. The present work provides an
overview of the highlights of a major new contribution to the understanding
of this issue based on the data and analysis of the EMeRGe (Effect of Megacities on the transport and transformation of
pollutants on the Regional to Global scales) international project. EMeRGe focuses on atmospheric
chemistry, dynamics, and transport of local and regional pollution
originating in MPCs. Airborne measurements, taking advantage of the long
range capabilities of the High Altitude and LOng Range Research Aircraft
(HALO, https://www.halo-spp.de, last access: 22 March 2022), are a central part of the project. The synergistic
use and consistent interpretation of observational data sets of different
spatial and temporal resolution (e.g. from ground-based networks, airborne
campaigns, and satellite measurements) supported by modelling within EMeRGe
provide unique insight to test the current understanding of MPC pollution outflows.
In order to obtain an adequate set of measurements at different spatial
scales, two field experiments were positioned in time and space to contrast
situations when the photochemical transformation of plumes emerging from
MPCs is large. These experiments were conducted in summer 2017 over Europe
and in the inter-monsoon period over Asia in spring 2018. The intensive
observational periods (IOPs) involved HALO airborne measurements of ozone and
its precursors, volatile organic compounds, aerosol particles, and related
species as well as coordinated ground-based ancillary observations at
different sites. Perfluorocarbon (PFC) tracer releases and model forecasts
supported the flight planning, the identification of pollution plumes, and
the analysis of chemical transformations during transport.
This paper describes the experimental deployment and scientific questions of
the IOP in Europe. The MPC targets – London (United Kingdom; UK), the Benelux/Ruhr area
(Belgium, the Netherlands, Luxembourg and Germany), Paris (France), Rome and the
Po Valley (Italy), and Madrid and Barcelona (Spain) – were investigated during seven
HALO research flights with an aircraft base in Germany for a total of 53 flight
hours. An in-flight comparison of HALO with the collaborating UK-airborne
platform Facility for Airborne Atmospheric Measurements (FAAM) took place to assure accuracy and comparability of the
instrumentation on board.
Overall, EMeRGe unites measurements of near- and far-field emissions and
hence deals with complex air masses of local and distant sources. Regional
transport of several European MPC outflows was successfully identified and
measured. Chemical processing of the MPC emissions was inferred from
airborne observations of primary and secondary pollutants and the ratios
between species having different chemical lifetimes. Photochemical
processing of aerosol and secondary formation or organic acids was evident
during the transport of MPC plumes. Urban plumes mix efficiently with natural
sources as mineral dust and with biomass burning emissions from vegetation
and forest fires. This confirms the importance of wildland fire emissions in
Europe and indicates an important but discontinuous contribution to the
European emission budget that might be of relevance in the design of
efficient mitigation strategies.
The present work provides an overview of the most salient results in the
European context, with these being addressed in more detail within additional
dedicated EMeRGe studies. The deployment and results obtained in Asia will
be the subject of separate publications.
... Due to the high ratio between true air speed of the aircraft and the flow velocity inside the inlet line particles are sampled with enhanced efficiency relative to the gas phase. This approach has been already used during earlier observations, e.g. from NASA ER-2 (Fahey et al., 2001;Northway et al., 2002), NASA DC-8 (Weinheimer et al., 1998), or the DLR Falcon (Feigl et al., 1999;Ziereis et al., 2004). It was used to investigate the nitrate content of PSC particles as well as that of cirrus ice particles. ...
During winter 2015/2016, the Arctic stratosphere was characterized
by extraordinarily low temperatures in connection with a very strong polar
vortex and with the occurrence of extensive polar stratospheric clouds. From
mid-December 2015 until mid-March 2016, the German research aircraft
HALO (High Altitude and Long-Range Research Aircraft) was deployed to probe
the lowermost stratosphere in the Arctic region within the POLSTRACC (Polar
Stratosphere in a Changing Climate) mission. More than 20 flights have
been conducted out of Kiruna, Sweden, and Oberpfaffenhofen, Germany, covering
the whole winter period. Besides total reactive nitrogen (NOy),
observations of nitrous oxide, nitric acid, ozone, and water were used for
this study. Total reactive nitrogen and its partitioning between the gas and
particle phases are key parameters for understanding processes controlling
the ozone budget in the polar winter stratosphere. The vertical
redistribution of total reactive nitrogen was evaluated by using
tracer–tracer correlations (NOy–N2O and NOy–O3). The
trace gases are well correlated as long as the NOy distribution is
controlled by its gas-phase production from N2O. Deviations of the
observed NOy from this correlation indicate the influence of
heterogeneous processes. In early winter no such deviations have been
observed. In January, however, air masses with extensive nitrification were
encountered at altitudes between 12 and 15 km. The excess NOy amounted
to about 6 ppb. During several flights, along with gas-phase
nitrification, indications for extensive occurrence of nitric acid
containing particles at flight altitude were found. These observations
support the assumption of sedimentation and subsequent evaporation of nitric acid-containing particles, leading to redistribution of total reactive
nitrogen at lower altitudes. Remnants of nitrified air masses have been
observed until mid-March. Between the end of February and mid-March,
denitrified air masses have also been observed in connection with high
potential temperatures. This indicates the downward transport of air masses
that have been denitrified during the earlier winter phase. Using
tracer–tracer correlations, missing total reactive nitrogen was estimated
to amount to 6 ppb. Further, indications of transport and mixing of these
processed air masses outside the vortex have been found, contributing to the
chemical budget of the winter lowermost stratosphere. Observations within
POLSTRACC, at the bottom of the vortex, reflect heterogeneous processes from
the overlying Arctic winter stratosphere. The comparison of the observations
with CLaMS model simulations confirm and complete the picture arising from
the present measurements. The simulations confirm that the ensemble of all
observations is representative of the vortex-wide vertical
NOy redistribution.
... The above studies focused on trace gases linked to air quality and provided relatively sparse information on GHGs. Long-lived greenhouse gases such as CH 4 and CO 2 emitted from individual European urban areas have been investigated in airborne and ground-based studies, e.g. for London (O'Shea et al., 2014;Helfter et al., 2016;Pitt et al., 2019), Paris (Bréon et al., 2015;Lian et al., 2019), Cracow (Kuc et al., 2003;Zimnoch et al., 2019), Berlin , and Rome (Gioli et al., 2014). Collectively, they report on inconsistencies between the current emission inventories and measurements. ...
EMeRGe provides a unique set of in situ and remote sensing airborne measurements of trace gases and aerosol particles along selected flight routes in the lower troposphere over Europe. The interpretation uses also complementary collocated ground-based and satellite measurements. The collected data help to improve the current understanding of the complex spatial distribution of trace gases and aerosol particles resulting from mixing, transport, and transformation of pollution plumes over Europe.
... Oxides Measuring System (AENEAS; Ziereis et al., 2004) was also on board and provided NO y and NO data products. In ...
This paper presents measurements of ozone, water vapour and nitric acid in the upper troposphere/lower stratosphere (UTLS) over North Atlantic and Europe. The measurements were acquired with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the Wave Driven Isentropic Exchange (WISE) campaign in October 2017. GLORIA is an airborne limb imager capable of acquiring both 2-D data sets (curtains along the flight path) and, when the carrier aircraft is flying around the observed air mass, spatially highly resolved 3-D tomographic data. Here we present a case study of a Rossby wave (RW) breaking event observed during two subsequent flights two days apart. RW breaking is known to steepen tracer gradients and facilitate stratosphere-troposphere exchange (STE). Our measurements reveal complex spatial structures in stratospheric tracers (ozone and nitric acid) with multiple vertically stacked filaments. Backward trajectory analysis is used to demonstrate that these features are related to several previous Rossby wave breaking events and that the small-scale structure of the UTLS in the Rossby wave breaking region, which is otherwise very hard to observe, can be understood as stirring and mixing of air masses of tropospheric and stratospheric origin. It is also shown that a strong nitric acid enhancement observed just above the tropopause is likely a result of NOx production by lightning activity. The measurements showed signatures of enhanced mixing between stratospheric and tropospheric air near the polar jet with some transport of water vapour into the stratosphere. Some of the air masses seen in 3-D data were encountered again two days later, stretched to very thin filament (horizontal thickness down to 30 km at some altitudes) rich in stratospheric tracers. This repeated measurement allowed us to directly observe and analyse the progress of mixing processes in a thin filament over two days. Our results provide direct insight into small-scale dynamics of the UTLS in the Rossby wave breaking region, witch is of great importance to understanding STE and poleward transport in the UTLS.
... The measurements shown in Fig. 2c are based on the subisokinetic sampling of particles with a forward-looking inlet (e.g. Fahey et al., 1989;Ziereis et al., 2004). Particles larger than a few tenths of a micrometre are sampled with enhanced efficiency and are detected as gas-phase equivalent NO * y . ...
The Arctic winter 2015–2016 was characterized by exceptionally low stratospheric temperatures, favouring the formation of polar stratospheric clouds (PSCs) from mid-December until the end of February down to low stratospheric altitudes. Observations by GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) on HALO (High Altitude and LOng range research aircraft) during the PGS (POLSTRACC–GW-LCYCLE II–SALSA) campaign from December 2015 to March 2016 allow the investigation of the influence of denitrification on the lowermost stratosphere (LMS) with a high spatial resolution.
Two-dimensional vertical cross sections of nitric acid (HNO3) along the flight track and tracer–tracer correlations derived from the GLORIA observations document detailed pictures of wide-spread nitrification of the Arctic LMS during the course of an entire winter. GLORIA observations show large-scale structures and local fine structures with enhanced absolute HNO3 volume mixing ratios reaching up to 11 ppbv at altitudes of 13 km in January and nitrified filaments persisting until the middle of March. Narrow coherent structures tilted with altitude of enhanced HNO3, observed in mid-January, are interpreted as regions recently nitrified by sublimating HNO3-containing particles.
Overall, extensive nitrification of the LMS between 5.0 and 7.0 ppbv at potential temperature levels between 350 and 380 K is estimated.
The GLORIA observations are compared with CLaMS (Chemical Lagrangian Model of the Stratosphere) simulations. The fundamental structures observed by GLORIA are well reproduced, but differences in the fine structures are diagnosed. Further, CLaMS predominantly underestimates the spatial extent of HNO3 maxima derived from the GLORIA observations as well as the overall nitrification of the LMS. Sensitivity simulations with CLaMS including (i) enhanced sedimentation rates in case of ice supersaturation (to resemble ice nucleation on nitric acid trihydrate (NAT)), (ii) a global temperature offset, (iii) modified growth rates (to resemble aspherical particles with larger surfaces) and (iv) temperature fluctuations (to resemble the impact of small-scale mountain waves) slightly improved the agreement with the GLORIA observations of individual flights. However, no parameter could be isolated which resulted in a general improvement for all flights. Still, the sensitivity simulations suggest that details of particle microphysics play a significant role for simulated LMS nitrification in January, while air subsidence, transport and mixing become increasingly important for the simulated HNO3 distributions towards the end of the winter.
... The measurements shown in Fig. 2c are based on the subisokinetic sampling of particles with a forward-looking inlet (e.g. Fahey et al., 1989;Ziereis et al., 2004). Particles larger than a few tenths of a micrometre are sampled with enhanced efficiency and are detected as gas-phase equivalent NO * y . ...
Observation of nitrification of the lowermost stratosphere during the cold Arctic winter 2015 using the Research aircaraft HALO.
... Since the early 1990s chemiluminescence detectors have been used for observations in the free troposphere and lower stratosphere (e.g. Huntrieser et al., 2002;Schlager et al., 1997;Ziereis et al., 2004). ...
Nitrogen oxide (NO and NOy) measurements were performed onboard an in-service aircraft within the framework of CARIBIC (Civil Aircraft for the Regular Investigation of the atmosphere Based on an Instrument Container). A total of 330 flights were completed from May 2005 through April 2013 between Frankfurt/Germany and destination airports in Canada, the USA, Brazil, Venezuela, Chile, Argentina, Colombia, South Africa, China, South Korea, Japan, India, Thailand, and the Philippines. Different regions show differing NO and NOy mixing ratios. In the mid-latitudes, observed NOy and NO generally shows clear seasonal cycles in the upper troposphere with a maximum in summer and a minimum in winter. Mean NOy mixing ratios vary between 1.36 nmol/mol in summer and 0.27 nmol/mol in winter. Mean NO mixing ratios range between 0.05 nmol/mol and 0.22 nmol/mol. Regions south of 40 °N show no consistent seasonal dependence. Based on CO observations, low, median and high CO air masses were defined. According to this classification, more data was obtained in high CO air masses in the regions south of 40 °N compared to the midlatitudes. This indicates that boundary layer emissions are more important in these regions. In general, NOy mixing ratios are highest when measured in high CO air masses. This dataset is one of the most comprehensive NO and NOy dataset available today for the upper troposphere and is therefore highly suitable for the validation of atmosphere-chemistry-models.
... Both HO 2 NO 2 (Ulrich et al., 2012) and HNO 3 ( Bartels-Rausch et al., 2002;Hudson et al., 2002;Ullerstam et al., 2005) have been shown in laboratory experiments to adsorb to ice surfaces. This conclusion is supported by field observations which have confirmed uptake of both HNO 3 and HO 2 NO 2 to snow surfaces Slusher et al., 2002), and of HNO 3 to cirrus clouds (Weinheimer et al., 1998;Popp et al., 2004;Ziereis et al., 2004). In general, therefore, in snow covered areas, or indeed regions of the atmosphere with lofted snow/ice, such as cirrus clouds or blowing/precipitating snow, physical adsorption of HNO 3 and HO 2 NO 2 from the air to the snow/ice is likely to occur. ...
Observations of peroxynitric acid (HO2NO2) and nitric acid (HNO3) were made during a 4 month period of Antarctic winter darkness at the coastal Antarctic research station, Halley. Mixing ratios of HNO3 ranged from instrumental detection limits to ~8 parts per trillion by volume (pptv), and of HO2NO2 from detection limits to ~5 pptv; the average ratio of HNO3 : HO2NO2 was 2.0(± 0.6) : 1, with HNO3 always present at greater mixing ratios than HO2NO2 during the winter darkness. An extremely strong association existed for the entire measurement period between mixing ratios of the respective trace gases and temperature: for HO2NO2, R2 = 0.72, and for HNO3, R2 = 0.70. We focus on three cases with considerable variation in temperature, where wind speeds were low and constant, such that, with the lack of photochemistry, changes in mixing ratio were likely to be driven by physical mechanisms alone. We derived enthalpies of adsorption (ΔHads) for these three cases. The average ΔHads for HNO3 was −42 ± 2 kJ mol−1 and for HO2NO2 was −56 ± 1 kJ mol−1; these values are extremely close to those derived in laboratory studies. This exercise demonstrates (i) that adsorption to/desorption from the snow pack should be taken into account when addressing budgets of boundary layer HO2NO2 and HNO3 at any snow-covered site, and (ii) that Antarctic winter can be used as a natural "laboratory in the field" for testing data on physical exchange mechanisms.
... Both HO 2 NO 2 (Ulrich et al., 2012) and HNO 3 (Bartels-Rausch et al., 2002;Hudson 20 et al., 2002;Ullerstam et al., 2005) have been shown in laboratory experiments to adsorb to ice surfaces. This conclusion is supported by field observations which have confirmed uptake of both HNO 3 and HO 2 NO 2 to snow surfaces Slusher et al., 2002), and of HNO 3 to cirrus clouds (Weinheimer et al., 1998;Popp et al., 2004; Ziereis et al., 2004). In general, therefore, in snow covered areas, or indeed regions of the atmosphere with lofted snow/ice, such as cirrus clouds or blowing/precipitating snow, physical adsorption of HNO 3 and HO 2 NO 2 from the air to the snow/ice is likely to occur. ...
Observations of peroxynitric acid (HO2NO2) and nitric acid (HNO3) were made during a 4 month period of Antarctic winter darkness at the coastal Antarctic research station, Halley. Mixing ratios of HNO3 ranged from instrumental detection limits to ∼8 parts per trillion by volume (pptv), and of HO2NO2 from detection limits to ∼5 pptv; the average ratio of HNO3 : HO2NO2 was 2.0(± 0.6):1, with HNO3 always present at greater mixing ratios than HO2NO2 during the winter darkness. An extremely strong association existed for the entire measurement period between mixing ratios of the respective trace gases and temperature: for HO2NO2, R² = 0.72, and for HNO3, R² = 0.70. We focus on three cases with considerable variation in temperature, where wind speeds were low and constant, such that, with the lack of photochemistry, changes in mixing ratio were likely to be driven by adsorption/desorption mechanisms alone. We derived enthalpies of adsorption (ΔHads) for these three cases. The average ΔHads for HNO3 was −42 ± 7 kJ mol⁻¹ and for HO2NO2 was −56 ± 3 kJ mol⁻¹; these values are extremely close to laboratory-derived values. This exercise demonstrates (i) that adsorption to/desorption from the snow pack should be taken into account when addressing budgets of boundary layer HO2NO2 and HNO3 at any snow-covered site, and (ii) that Antarctic winter can be used as a~natural "laboratory in the field" for testing data on physical exchange mechanisms.
... A phosphorous coated pen-ray lamp (Jelight Corp.) located in the centre of the reaction vessel photolyzes acetone efficiently at wavelengths around 285 nm, but does not significantly photolyze NO 2 and PAN (Warneck and Zerbach, 1992; Flocke et al., 2005b). The PCS was characterized in detail with the help of our NO/NO 2 /NO y measurement system described elsewhere (Ziereis et al., 2004 ) and has a NO to PAN conversion efficiency of 92 ± 5% with the remainder mainly in the form of NO 2 . These results are comparable with similar PAN sources described in the literature (Volz-Thomas et al., 2002; Flocke et al., 2005b). ...
... The PCS was characterized in detail with the help of our NO/NO 2 /NO y measurement system described elsewhere ( Ziereis et al., 2004) and has a NO to PAN conversion efficiency of 92 ± 5% with the remainder mainly in the form of NO 2. These results are comparable with similar PAN sources described in the literature ( Volz-Thomas et al., 2002;Flocke et al., 2005b). ...
An airborne chemical ionization ion trap mass spectrometer instrument (CI-ITMS) has been developed for tropospheric and stratospheric fast in-situ measurements of PAN (peroxyacetyl nitrate) and PPN (peroxypropionyl nitrate). The first scientific deployment of the FASTPEX instrument (FASTPEX = Fast Measurement of Peroxyacyl nitrates) took place in the Arctic during 18 missions aboard the DLR research aircraft Falcon, within the framework of the POLARCAT-GRACE campaign in the summer of 2008. The FASTPEX instrument is described and characteristic properties of the employed ion trap mass spectrometer are discussed. Atmospheric data obtained at altitudes of up to ~12 km are presented, from the boundary layer to the lowermost stratosphere. Data were sampled with a time resolution of 2 s and a 2σ detection limit of 25 pmol mol−1. An isotopically labelled standard was used for a permanent online calibration. For this reason the accuracy of the PAN measurements is better than ±10% for mixing ratios greater than 200 pmol mol−1. PAN mixing ratios in the summer Arctic troposphere were in the order of a few hundred pmol mol−1 and generally correlated well with CO. In the Arctic boundary layer and lowermost stratosphere smaller PAN mixing ratios were observed due to a combination of missing local sources of PAN precursor gases and efficient removal processes (thermolysis/photolysis). PPN, the second most abundant PAN homologue, was measured simultanously. Observed PPN/PAN ratios range between ~0.03 and 0.3
