53 research outputs found
2018 Bird Strike Committee USA Meeting
Offshore Aviation in Brazil Since1980
Air passenger and cargo transport to offshore platforms began in the 1980s. The largest customer in Brazil is PETROBRAS, which ranked fifth in 2011 among the largest publicly traded oil companies in the world. Air passenger and Cargo Transport Medical Evacuation Helicopter Maintenance Helicopter Transport of External Cargo
Polariton bandstructure of disordered metallic photonic crystal slabs
We analyze the influence of disorder on the polaritonic bandstructure of metallic photonic crystal slabs. Different disorder types with varying next-neighbor correlations and disorder amounts are implemented. Angle-resolved transmission measurements allow to determine the relation of bandstructure and disorder. It is found that uncorrelated disorder retains the bandstructure and only reduces the splitting between the gaps. Correlated disorder, however, leads to the complete destruction of the bandstructure for moderate disorder amounts due to the excitation of different modes. We present a model that shows a good agreement with the measurements
Modeling the Sources and Chemistry of Polar Tropospheric Halogens (Cl, Br, and I) Using the CAM-Chem Global Chemistry-Climate Model
31 pags., 12 figs., 6 tabs. -- Open Access funded by Creative Commons Atribution Licence 4.0. -- jame20925-sup-0001_Supporting_Information.pdfCurrent chemistry climate models do not include polar emissions and chemistry of halogens. This work presents the first implementation of an interactive polar module into the very short-lived (VSL) halogen version of the Community Atmosphere Model with Chemistry (CAM-Chem) model. The polar module includes photochemical release of molecular bromine, chlorine, and interhalogens from the sea-ice surface, and brine diffusion of iodine biologically produced underneath and within porous sea-ice. It also includes heterogeneous recycling of inorganic halogen reservoirs deposited over fresh sea-ice surfaces and snow-covered regions. The polar emission of chlorine, bromine, and iodine reach approximately 32, 250, and 39 Gg/year for Antarctica and 33, 271, and 4 Gg/year for the Arctic, respectively, with a marked seasonal cycle mainly driven by sunlight and sea-ice coverage. Model results are validated against polar boundary layer measurements of ClO, BrO, and IO, and satellite BrO and IO columns. This validation includes satellite observations of IO over inner Antarctica for which an iodine “leapfrog” mechanism is proposed to transport active iodine from coastal source regions to the interior of the continent. The modeled chlorine and bromine polar sources represent up to 45% and 80% of the global biogenic VSL and VSL emissions, respectively, while the Antarctic sea-ice iodine flux is ~10 times larger than that from the Southern Ocean. We present the first estimate of the contribution of polar halogen emissions to the global tropospheric halogen budget. CAM-Chem includes now a complete representation of halogen sources and chemistry from pole-to-pole and from the Earth's surface up to the stratopause.This study has been funded by the European Research Council Executive Agency under the European Union′s Horizon 2020 Research and Innovation
program (Project “ERC‐2016‐COG 726349 CLIMAHAL”) and supported by the Consejo Superior de Investigaciones Científicas (CSIC) of Spain. Computing
resources, support, and data storage are provided and maintained by the Computational and Information System Laboratory from the National
Center of Atmospheric Research (CISL,2017). R. P. F. would like to thank CONICET, ANPCyT (PICT 2015‐0714), UNCuyo (SeCTyP M032/3853), and
UTN (PID 4920‐194/2018) for the financial support. Partial funding for this work was provided by the Korea Polar Research Institute (KOPRI) project (PE18200). The contributions of the University of Bremen have been supported by the State of Bremen, the German Research Foundation (DFG),
the German Aerospace (DLR), and the European Space Agency (ESA). We gratefully acknowledge the funding by the Deutsche Forschungsgemeinschaft
(DFG, German Research Foundation) —Projektnummer 268020496—TRR 172, within the Transregional Collaborative Research Center “ArctiC
Amplification: Climate Relevant Atmospheric and SurfaCe Processes,and Feedback Mechanisms (AC)3 ” in subproject C03 as well as the support by
the University of Bremen Institutional Strategy Measure M8 in the framework of the DFG Excellence Initiative
Seasonality of halogen deposition in polar snow and ice
Abstract. The atmospheric chemistry of iodine and bromine in Polar regions is of interest due to the key role of halogens in many atmospheric processes, particularly tropospheric ozone destruction. Bromine is emitted from the open ocean but is enriched above first-year sea ice during springtime bromine explosion events, whereas iodine emission is attributed to biological communities in the open ocean and hosted by sea ice. It has been previously demonstrated that bromine and iodine are present in Antarctic ice over glacial–interglacial cycles. Here we investigate seasonal variability of bromine and iodine in polar snow and ice, to evaluate their emission, transport and deposition in Antarctica and the Arctic and better understand potential links to sea ice. We find that bromine and iodine concentrations and Br enrichment (relative to sea salt content) in polar ice do vary seasonally in Arctic snow and Antarctic ice. Although seasonal variability in halogen emission sources is recorded by satellite-based observations of tropospheric halogen concentrations, seasonal patterns observed in snowpack are likely also influenced by photolysis-driven processes. Peaks of bromine concentration and Br enrichment in Arctic snow and Antarctic ice occur in spring and summer, when sunlight is present. A secondary bromine peak, observed at the end of summer, is attributed to bromine deposition at the end of the polar day. Iodine concentrations are largest in winter Antarctic ice strata, contrary to contemporary observations of summer maxima in iodine emissions. These findings support previous observations of iodine peaks in winter snow strata attributed to the absence of sunlight-driven photolytic re-mobilisation of iodine from surface snow. Further investigation is required to confirm these proposed mechanisms explaining observations of halogens in polar snow and ice, and to evaluate the extent to which halogens may be applied as sea ice proxies
Canadian Arctic sea ice reconstructed from bromine in the Greenland NEEM ice core
Reconstructing the past variability of Arctic sea ice provides an essential context for recent multi-year sea ice decline, although few quantitative reconstructions cover the Holocene period prior to the earliest historical records 1,200 years ago. Photochemical recycling of bromine is observed over first-year, or seasonal, sea ice in so-called "bromine explosions" and we employ a 1-D chemistry transport model to quantify processes of bromine enrichment over first-year sea ice and depositional transport over multi-year sea ice and land ice. We report bromine enrichment in the Northwest Greenland Eemian NEEM ice core since the end of the Eemian interglacial 120,000 years ago, finding the maximum extension of first-year sea ice occurred approximately 9,000 years ago during the Holocene climate optimum, when Greenland temperatures were 2 to 3 degrees C above present values. First-year sea ice extent was lowest during the glacial stadials suggesting complete coverage of the Arctic Ocean by multi-year sea ice. These findings demonstrate a clear relationship between temperature and first-year sea ice extent in the Arctic and suggest multi-year sea ice will continue to decline as polar amplification drives Arctic temperatures beyond the 2 degrees C global average warming target of the recent COP21 Paris climate agreement
Intercomparison of NO2, O4, O3 and HCHO slant column measurements by MAX-DOAS and zenith-sky UV¿visible spectrometers during CINDI-2
40 pags., 22 figs., 13 tabs.In September 2016, 36 spectrometers from 24 institutes measured a number of key atmospheric pollutants for a period of 17¿d during the Second Cabauw Intercomparison campaign for Nitrogen Dioxide measuring Instruments (CINDI-2) that took place at Cabauw, the Netherlands (51.97¿¿N, 4.93¿¿E). We report on the outcome of the formal semi-blind intercomparison exercise, which was held under the umbrella of the Network for the Detection of Atmospheric Composition Change (NDACC) and the European Space Agency (ESA). The three major goals of CINDI-2 were (1) to characterise and better understand the differences between a large number of multi-axis differential optical absorption spectroscopy (MAX-DOAS) and zenith-sky DOAS instruments and analysis methods, (2) to define a robust methodology for performance assessment of all participating instruments, and (3) to contribute to a harmonisation of the measurement settings and retrieval methods. This, in turn, creates the capability to produce consistent high-quality ground-based data sets, which are an essential requirement to generate reliable long-term measurement time series suitable for trend analysis and satellite data validation.
The data products investigated during the semi-blind intercomparison are slant columns of nitrogen dioxide (NO2), the oxygen collision complex (O4) and ozone (O3) measured in the UV and visible wavelength region, formaldehyde (HCHO) in the UV spectral region, and NO2 in an additional (smaller) wavelength range in the visible region. The campaign design and implementation processes are discussed in detail including the measurement protocol, calibration procedures and slant column retrieval settings. Strong emphasis was put on the careful alignment and synchronisation of the measurement systems, resulting in a unique set of measurements made under highly comparable air mass conditions.
The CINDI-2 data sets were investigated using a regression analysis of the slant columns measured by each instrument and for each of the target data products. The slope and intercept of the regression analysis respectively quantify the mean systematic bias and offset of the individual data sets against the selected reference (which is obtained from the median of either all data sets or a subset), and the rms error provides an estimate of the measurement noise or dispersion. These three criteria are examined and for each of the parameters and each of the data products, performance thresholds are set and applied to all the measurements. The approach presented here has been developed based on heritage from previous intercomparison exercises. It introduces a quantitative assessment of the consistency between all the participating instruments for the MAX-DOAS and zenith-sky DOAS techniques.CINDI-2 received funding from the Netherlands Space Office (NSO). Funding for this study was provided
by ESA through the CINDI-2 (ESA contract no. 4000118533/16/ISbo) and FRM4DOAS (ESA contract no. 4000118181/16/I-EF)
projects and partly within the EU 7th Framework Programme
QA4ECV project (grant agreement no. 607405). The BOKU
MAX-DOAS instrument was funded and the participation of Stefan F. Schreier was supported by the Austrian Science Fund
(FWF): I 2296-N29. The participation of the University of Toronto
team was supported by the Canadian Space Agency (through
the AVATARS project) and the Natural Sciences and Engineering Research Council (through the PAHA project). The instrument was primarily funded by the Canada Foundation for Innovation and is usually operated at the Polar Environment Atmospheric Research Laboratory (PEARL) by the Canadian Network
for the Detection of Atmospheric Change (CANDAC). Funding for
CISC was provided by the UVAS (“Ultraviolet and Visible Atmospheric Sounder”) projects SEOSAT/INGENIO, ESP2015-71299-
R, MINECO-FEDER and UE. The activities of the IUP-Heidelberg
were supported by the DFG project RAPSODI (grant no. PL
193/17-1). SAOZ and Mini-SAOZ instruments are supported by the
Centre National de la Recherche Scientifique (CNRS) and the Centre National d’Etudes Spatiales (CNES). INTA recognises support
from the National funding projects HELADO (CTM2013-41311-P) and AVATAR (CGL2014-55230-R). AMOIAP recognises support from the Russian Science Foundation (grant no. 16-17-10275) and the Russian Foundation for Basic Research (grant nos. 16-05-
01062 and 18-35-00682). Ka L. Chan received transnational access funding from ACTRIS-2 (H2020 grant agreement no. 654109).
Rainer Volkamer recognises funding from NASA’s Atmospheric Composition Program (NASA-16-NUP2016-0001) and the US National Science Foundation (award AGS-1620530). Henning Finkenzeller is the recipient of a NASA graduate fellowship. Mihalis Vrekoussis recognises support from the University of Bremen and the DFG Research Center/Cluster of Excellence “The Ocean in the
Earth System-MARUM”. Financial support through the University of Bremen Institutional Strategy in the framework of the
DFG Excellence Initiative is gratefully appreciated for Anja Schönhardt. Pandora instrument deployment was supported by Luftblick
through the ESA Pandonia Project and NASA Pandora Project at the Goddard Space Flight Center under NASA Headquarters’ Tropospheric Composition Program. The article processing charges for
this open-access publication were covered by BK Scientific
Short-Lived Trace Gases in the Surface Ocean and the Atmosphere
The two-way exchange of trace gases between the ocean and the atmosphere is important for both the chemistry and physics of the atmosphere and the biogeochemistry of the oceans, including the global cycling of elements. Here we review these exchanges and their importance for a range of gases whose lifetimes are generally short compared to the main greenhouse gases and which are, in most cases, more reactive than them. Gases considered include sulphur and related compounds, organohalogens, non-methane hydrocarbons, ozone, ammonia and related compounds, hydrogen and carbon monoxide. Finally, we stress the interactivity of the system, the importance of process understanding for modeling, the need for more extensive field measurements and their better seasonal coverage, the importance of inter-calibration exercises and finally the need to show the importance of air-sea exchanges for global cycling and how the field fits into the broader context of Earth System Science
Observations of iodine monoxide (IO) columns from satellite
International audienceIodine species in the troposphere are linked to ozone depletion and new particle formation. In this study, a full year of iodine monoxide (IO) columns retrieved from measurements of the SCIAMACHY satellite instrument is presented, alongside a discussion of their uncertainties and the detection limit. The largest amounts of IO are found near springtime Antarctica, where ground-based measurements have positively detected iodine compounds before. A seasonal variation of iodine monoxide in Antarctica is revealed with high values in springtime, slightly less IO in the summer period and again larger amounts in autumn. In winter, no elevated IO levels are found in the areas accessible to satellite measurements. This seasonal cycle is in good agreement with recent ground-based measurements in Antarctica. In the Arctic region, no elevated IO levels were found in the whole time period analysed, arguing for different conditions existing in the two Polar Regions. To investigate possible release mechanisms such as inorganic release or biogenic precursors, comparisons of IO results with tropospheric BrO maps, measurements of chlorophyll concentration, and ice coverage are discussed. Some parallels and interesting differences between IO and BrO temporal and spatial distributions are pointed out. Although no full interpretation can be given at this point, the large spatial coverage of satellite measurements and the availability of a long-term dataset give some new indications and understandings of the abundances and distributions of iodine compounds in the troposphere
Space-based observation of volcanic iodine monoxide
Volcanic eruptions inject substantial amounts of halogens into the
atmosphere. Chlorine and bromine oxides have frequently been observed in
volcanic plumes from different instrumental platforms such as from ground, aircraft
and satellites. The present study is the first observational
evidence that iodine oxides are also emitted into the atmosphere during
volcanic eruptions. Large column amounts of iodine monoxide, IO, are observed
in satellite measurements following the major eruption of the Kasatochi
volcano, Alaska, in 2008. The IO signal is detected in measurements made both
by SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY) on
ENVISAT (Environmental Satellite) and GOME-2
(Global Ozone Monitoring Experiment-2) on MetOp-A (Meteorological Operational Satellite A).
Following the eruption on
7 August 2008, strongly elevated levels of IO slant columns of more than
4 × 1013 molec cm−2 are retrieved along the volcanic plume
trajectories for several days. The retrieved IO columns from the different
instruments are consistent, and the spatial distribution of the IO plume is
similar to that of bromine monoxide, BrO. Details in the spatial
distribution, however, differ between IO, BrO and sulfur dioxide,
SO2. The column amounts of IO are approximately 1 order of
magnitude smaller than those of BrO. Using the GOME-2A observations, the
total mass of IO in the volcanic plume injected into the atmosphere from the
eruption of Kasatochi on 7 August 2008, is determined to be on the order of
10 Mg
A wide field-of-view imaging DOAS instrument for two-dimensional trace gas mapping from aircraft
The Airborne imaging differential optical absorption
spectroscopy (DOAS) instrument for Measurements of
Atmospheric Pollution (AirMAP) has been developed for the
purpose of trace gas measurements and pollution mapping.
The instrument has been characterized and successfully operated
from aircraft. Nitrogen dioxide (NO2) columns were
retrieved from the AirMAP observations. A major benefit of
the push-broom imaging instrument is the spatially continuous,
gap-free measurement sequence independent of flight
altitude, a valuable characteristic for mapping purposes. This
is made possible by the use of a charge coupled device (CCD)
frame-transfer detector. A broad field of view across track
of around 48� is achieved with wide-angle entrance optics.
This leads to a swath width of about the same size as the
flight altitude. The use of fibre coupled light intake optics
with sorted light fibres allows flexible instrument positioning
within the aircraft and retains the very good imaging capabilities.
The measurements yield ground spatial resolutions
below 100m depending on flight altitude. The number of
viewing directions is chosen from a maximum of 35 individual
viewing directions (lines of sight, LOS) represented
by 35 individual fibres. The selection is adapted to each situation
by averaging according to signal-to-noise or spatial
resolution requirements. Observations at 30m spatial resolution
are obtained when flying at 1000m altitude and making
use of all 35 viewing directions. This makes the instrument
a suitable tool for mapping trace gas point sources and
small-scale variability. The position and aircraft attitude are
taken into account for accurate spatial mapping using the
Attitude and Heading Reference System of the aircraft. A
first demonstration mission using AirMAP was undertaken
in June 2011. AirMAP was operated on the AWI Polar-5
aircraft in the framework of the AIRMETH-2011 campaign.
During a flight above a medium-sized coal-fired power plant
in north-west Germany, AirMAP clearly detected the emission
plume downwind from the exhaust stack, with NO2 vertical
columns around 2�1016 molecules c
- …