96 research outputs found

    INTRUSION OF RECENT AIR IN POLAR STRATOSPHERE DURING SUMMER 2009 REVEALED BY BALLOON-BORNE IN SITU CO MEASUREMENTS

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    International audienceThe SPIRALE (Spectroscopie Infa-Rouge par Absorption de Lasers Embarqués) balloon-borne instrument has been launched twice within 17 days in the polar region (Kiruna, Sweden, 67.9°N-21.1°E) during summer, at the beginning and at the end of August 2009. In situ measurements of several trace gases have been performed including CO and O 3 between 10 and 34 km height, with very high vertical resolution (~5 m). The both flight results are compared and the CO stratospheric profile of the first flight presents specific structures associated with mid-latitude intrusion in the lowest stratospheric levels. Their interpretation is made with the help of results from several modeling tools (MIMOSA and FLEXTRA) and available satellite data (IASI). We also used the O 3 profile correlated with CO to calculate the proportion of recent air in the polar stratosphere. The results indicate the impact of East Asia urban pollution on the chemistry of polar stratosphere in summer

    Validation and data characteristics of methane and nitrous oxide profiles observed by MIPAS and processed with Version 4.61 algorithm

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    The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-borne, aircraft, satellite and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign or ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH4 and N2O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61, full resolution MIPAS data covering the period 9 July 2002 to 26 March 2004) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. In the middle stratosphere, no significant bias is observed between MIPAS and correlative measurements, and MIPAS is providing a very consistent and global picture of the distribution of CH4 and N2O in this region. In average, the MIPAS CH4 values show a small positive bias in the lower stratosphere of about 5%. A similar situation is observed for N2O with a positive bias of 4%. In the lower stratosphere/upper troposphere (UT/LS) the individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH4 and N2O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH4 and N2O profiles are behaving as expected from the internal error estimation of IPF v4.61 and the estimated errors of the correlative measurements

    Validation of MIPAS HNO3 operational data

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    Nitric acid (HNO3) is one of the key products that are operationally retrieved by the European Space Agency (ESA) from the emission spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT. The product version 4.61/4.62 for the observation period between July 2002 and March 2004 is validated by comparisons with a number of independent observations from ground-based stations, aircraft/balloon campaigns, and satellites. Individual HNO3 profiles of the ESA MIPAS level-2 product show good agreement with those of MIPAS-B and MIPAS-STR (the balloon and aircraft version of MIPAS, respectively), and the balloon-borne infrared spectrometers MkIV and SPIRALE, mostly matching the reference data within the combined instrument error bars. In most cases differences between the correlative measurement pairs are less than 1 ppbv (5-10%) throughout the entire altitude range up to about 38 km (similar to 6 hPa), and below 0.5 ppbv (15-20% or more) above 30 km (similar to 17 hPa). However, differences up to 4 ppbv compared to MkIV have been found at high latitudes in December 2002 in the presence of polar stratospheric clouds. The degree of consistency is further largely affected by the temporal and spatial coincidence, and differences of 2 ppbv may be observed between 22 and 26 km (similar to 50 and 30 hPa) at high latitudes near the vortex boundary, due to large horizontal inhomogeneity of HNO3. Similar features are also observed in the mean differences of the MIPAS ESA HNO3 VMRs with respect to the ground-based FTIR measurements at five stations, aircraft-based SAFIRE-A and ASUR, and the balloon campaign IBEX. The mean relative differences between the MIPAS and FTIR HNO3 partial columns are within +/- 2%, comparable to the MIPAS systematic error of similar to 2%. For the vertical profiles, the biases between the MIPAS and FTIR data are generally below 10% in the altitudes of 10 to 30 km. The MIPAS and SAFIRE HNO3 data generally match within their total error bars for the mid and high latitude flights, despite the larger atmospheric inhomogeneities that characterize the measurement scenario at higher latitudes. The MIPAS and ASUR comparison reveals generally good agreements better than 10-13% at 20-34 km. The MIPAS and IBEX measurements agree reasonably well (mean relative differences within +/- 15%) between 17 and 32 km. Statistical comparisons of the MIPAS profiles correlated with those of Odin/SMR, ILAS-II, and ACE-FTS generally show good consistency. The mean differences averaged over individual latitude bands or all bands are within the combined instrument errors, and generally within 1, 0.5, and 0.3 ppbv between 10 and 40 km (similar to 260 and 4.5 hPa) for Odin/SMR, ILAS-II, and ACE-FTS, respectively. The standard deviations of the differences are between 1 to 2 ppbv. The standard deviations for the satellite comparisons and for almost all other comparisons are generally larger than the estimated measurement uncertainty. This is associated with the temporal and spatial coincidence error and the horizontal smoothing error which are not taken into account in our error budget. Both errors become large when the spatial variability of the target molecule is high.Peer reviewe

    Validation of HNO3, ClONO2, and N2O5 from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)

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    The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO3, ClONO2, and N2O5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N2O5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO3, ClONO2, and N2O5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO3 and ClONO2 were also compared with measurements by ground-based Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv ±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within±10% between 10 and 36 km. ACE-FTS HNO3 partial columns (~15–30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8° S–76.5° N. Good agreement between ACE-FTS ClONO2 and MIPAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N2O5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N2O5 maximum (around 30 km). Mean absolute differences at lower altitudes (16–27 km) are typically −0.05 ppbv for MIPAS nighttime and ±0.02 ppbv for MIPAS daytime measurements

    Assessment for Decision-Makers Scientiic Assessment of Ozone Depletion: 2014 World Meteorological Organization United Nations Environment Programme National Oceanic and Atmospheric Administration National Aeronautics and Space Administration European Commission

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    Actions taken under the Montreal Protocol have led to decreases in the atmospheric abundance of controlledozone-depleting substances (ODSs), and are enabling the return of the ozone layer toward 1980 levels.• The sum of the measured tropospheric abundances of substances controlled under the MontrealProtocol continues to decrease. Most of the major controlled ODSs are decreasing largely as projected, andhydrochlorofluorocarbons (HCFCs) and halon-1301 are still increasing. Unknown or unreported sources of carbontetrachloride are needed to explain its abundance.• Measured stratospheric abundances of chlorine- and bromine-containing substances originating from thedegradation of ODSs are decreasing. By 2012, combined chlorine and bromine levels (as estimated by EquivalentEffective Stratospheric Chlorine, EESC) had declined by about 10–15% from the peak values of ten to fifteen years ago.Decreases in atmospheric abundances of methyl chloroform (CH3CCl3), methyl bromide (CH3Br), and chlorofluorocarbons(CFCs) contributed approximately equally to these reductions.• Total column ozone declined over most of the globe during the 1980s and early 1990s (by about 2.5% averagedover 60°S to 60°N). It has remained relatively unchanged since 2000, with indications of a small increase in totalcolumn ozone in recent years, as expected. In the upper stratosphere there is a clear recent ozone increase, whichclimate models suggest can be explained by comparable contributions from declining ODS abundances and upperstratospheric cooling caused by carbon dioxide increases.• The Antarctic ozone hole continues to occur each spring, as expected for the current ODS abundances. The Arcticstratosphere in winter/spring 2011 was particularly cold, which led to large ozone depletion as expected under theseconditions.• Total column ozone will recover toward the 1980 benchmark levels over most of the globe under full compliancewith the Montreal Protocol. This recovery is expected to occur before midcentury in midlatitudes and the Arctic, andsomewhat later for the Antarctic ozone hole.The Antarctic ozone hole has caused significant changes in Southern Hemispheresurface climate in the summer.• Antarctic lower stratospheric cooling due to ozone depletion is very likely the dominant cause of observedchanges in Southern Hemisphere tropospheric summertime circulation over recent decades, with associatedimpacts on surface temperature, precipitation, and the oceans. In the Northern Hemisphere, no robust link has beenfound between stratospheric ozone depletion and tropospheric climate.Changes in CO2 , N2O, and CH4 will have an increasing influence on the ozone layer as ODSs decline.• As controlled ozone-depleting substances decline, the evolution of the ozone layer in the second half of the21st century will largely depend on the atmospheric abundances of CO2, N2O, and CH4. Overall, increasing carbondioxide (CO2 ) and methane (CH4 ) elevate global ozone, while increasing nitrous oxide (N2O) further depletes globalozone. The Antarctic ozone hole is less sensitive to CO2, N2O, and CH4 abundances.• In the tropics, significant decreases in column ozone are projected during the 21st century. Tropical ozone levelsare only weakly affected by ODS decline; they are sensitive to circulation changes driven by CO2 , N2O, and CH4 increases.The climate benefits of the Montreal Protocol could be significantly offset by projectedemissions of HFCs used to replace ODSs.The Montreal Protocol and its Amendments and adjustments have made large contributions toward reducing global greenhouse gasemissions. In 2010, the decrease of annual ODS emissions under the Montreal Protocol is estimated to be about 10 gigatonnes of avoidedCO2-equivalent emissions per year, which is about five times larger than the annual emissions reduction target for the first commitmentperiod (2008–2012) of the Kyoto Protocol (from the Executive Summary of the Scientific Assessment of Ozone Depletion: 2010).11 GWP-weighted emissions, also known as CO2-equivalent emissions, are defined as the amount of gas emitted multiplied by its 100-year Global WarmingPotential (GWP). Part of the effect of ODSs as greenhouse gases is offset by the cooling due to changes in ozone.Executive SummaryES-2• The sum of the hydrofluorocarbons (HFCs) currently used as ODS replacements makes a small contribution of about 0.5gigatonnes CO2-equivalent emissions per year. These emissions are currently growing at a rate of about 7% per year andare projected to continue to grow.• If the current mix of these substances is unchanged, increasing demand could result in HFC emissions of up to 8.8gigatonnes CO2-equivalent per year by 2050, nearly as high as the peak emission of CFCs of about 9.5 gigatonnes CO2-equivalent per year in the late 1980s.2• Replacements of the current mix of high-Global Warming Potential (GWP) HFCs with low-GWP compounds or not-inkindtechnologies would essentially avoid these CO2-equivalent emissions.• Some of these candidate low-GWP compounds are hydrofluoro-olefins (HFOs), one of which (HFO-1234yf) yields thepersistent degradation product trifluoroacetic acid (TFA) upon atmospheric oxidation. While the environmental effectsof TFA are considered to be negligible over the next few decades, potential longer-term impacts could require futureevaluations due to the environmental persistence of TFA and uncertainty in future uses of HFOs.• By 2050, HFC banks are estimated to grow to as much as 65 gigatonnes CO2-equivalent. The climate change impact ofthe HFC banks could be reduced by limiting future use of high-GWP HFCs to avoid the accumulation of the bank, or bydestruction of the banks.Additional important issues relevant to the Parties to the Montreal Protocol and otherdecision-makers have been assessed.• Derived emissions of carbon tetrachloride (CCl4), based on its estimated lifetime and its accurately measured atmosphericabundances, have become much larger than those from reported production and usage over the last decade.• As of 2009, the controlled consumption of methyl bromide declined below the reported consumption for quarantineand pre-shipment (QPS) uses, which are not controlled by the Montreal Protocol.• Increased anthropogenic emissions of very short-lived substances (VSLS) containing chlorine and bromine, particularlyfrom tropical sources, are an emerging issue for stratospheric ozone. The relative contribution of these emissions couldbecome important as levels of ODSs controlled under the Montreal Protocol decline.• As the atmospheric abundances of ODSs continue to decrease over the coming decades, N2O, as the primary source ofnitrogen oxides in the stratosphere, will become more important in future ozone depletion.• Emissions of HFC-23, a by-product of HCFC-22 production, have continued despite mitigation efforts.• While ODS levels remain high, a large stratospheric sulfuric aerosol enhancement due to a major volcanic eruption orgeoengineering activities would result in a substantial chemical depletion of ozone over much of the globe.While past actions taken under the Montreal Protocol have substantially reduced ODS production andconsumption, additional, but limited, options are available to reduce future ozone depletion.Emissions from the current banks are projected to contribute more to future ozone depletion than those caused by future ODS production,assuming compliance with the Protocol.• Possible options to advance the return of the ozone layerto the 1980 level (analyses based on midlatitude EESC) areshown graphically. The cumulative effect of eliminationof emissions from all banks and production advances thisreturn by 11 years.Scientific Steering Committee : Ayité-Lô Nohende AjavonDavid J. KarolyMalcolm K. KoPaul A. NewmanJohn A. PyleA.R. RavishankaraTheodore G. ShepherdSusan SolomonCoordinating EditorChristine A. Enni

    Comparisons between high altitude ( 25 km-40 km) wind measurements deduced from balloon borne flights obtained the last twenty years and ERA-Interim Re-analysis : Preliminary results

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    International audienceThis study consists to retrieve wind data from trajectories of balloon flights, which can be considered as perfect tracers at high levels ( above 25 km), to provide an assessment of meteorological wind data coming from Era-interim Re-analysis and forecastsfrom ECMWF. We first present our database including 327 balloon flights from 1989 to 2011 and validate the methodology to deduce zonal and meridional winds. Balloon flights were operated by the CNES (French Spatial Agency). The large stratospheric balloons can reach ceilings in the range 25-40 km and the flight durations are from few hours to several days. The collected database covers various seasons and different locations: Polar region (Kiruna (North of Sweeden)), Mid-latitudes (Gap and Aire-sur-Adour (France)) and Tropics (Hawaii, Teresina and Bauru (Brazil), Niamey (Niger)). Geophysical conditions we analyze are: polar vortex, spring and summer turn around in polar region, mid-latitude circulation in spring and autumn, and in the tropic East and West phase of the Quasi Biennale Oscillation.The first goal of this study is evaluate the vertical variability of the wind (intensity and direction) at high altitude in order to improve Balloon trajectory forecasts during measurement campaign to help for the flight decision and drive the balloon during the flight, which is a major goal for the safety related for future balloon campaign. The second goal is to evaluate the ability of ECMWF model to represent and predict winds and the circulation in the mid-stratosphere. The method used to compare ECMWF results and wind measurement is presented including methodology for interpolating ECMWF results on our data grid. Whatever the region /season considered, preliminary results obtained highlight bias between Era-interim Re-analysis and our wind data. In the future we plan to extend our study to operational wind data from ECMWF

    Impact of Streamer Associated with Blue Jets on Stratospheric Ozone: a Model Study

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    International audienceIn the framework of the preparation of TARANIS space mission dedicated to the study of transient luminous events (TLEs), a detailed ion-neutral chemistry model has been developed to simulate the impact of blue jet streamers on stratospheric chemistry. It is based on the MIPLASMO model (Microphysical and Photochemical Lagrangian Model of Ozone) widely used over the last 20 years to interpret balloon and satellite measurements associated with stratospheric ozone. It considers the time evolution of 118 species including neutral and ions species, through a set of 1760 reactions. In addition, the neutral chemistry associated with ozone takes classical nitrogen, chlorine and bromine species into account. After model validation, we focus on the streamer representation in the model. We consider two streamer parametrizations, (i) an electric field pulse with constant value as a function of time during the event, (ii) a time-varying realistic electric field, which is the result of an electrodynamic streamer model. Simulations are performed from 20 km to 50 km altitude. Results obtained are analyzed in two different ways: (i) during the first 100 s to identify the major fast mechanism associated with excited species, (ii) during 2 days to evaluate the impact on neutral chemistry (ozone and NOx species). The modelling results indicate that the time evolution of both excited and neutral species volume mixing ratio are very sensitive to the considered streamer parametrization (pulse or realistic streamer) and the differences for two-day simulations are significant. We particularly focus on ozone loss in the mid-, high-stratosphere and ozone production in the low stratosphere as a function of altitude. We find that the impact of streamer parametrization on ozone depends on the altitude

    On the Accuracy of Stratospheric Meteorological Reanalyses Using Wind Measurements at High Altitude in the Stratosphere

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    International audienceThis study is motivated by the improvement of the knowledge of stratospheric dynamics and the evaluation of the ability of models to represent wind variability in the stratosphere. We deduce from the Zero Pressure Balloons trajectories, operated by CNES during the last decade, zonal and meridional wind to provide a unique database in the altitude range [25-40] km. The collected data are associated with ZBP flights launch during winter and summer in polar region above the Esrange (Sweden) launch base and in equatorial region above the Teresina (Brazil) during easterly and westerly Quasibiennal Oscillation phase. We performed systematic comparisons between wind measurements and ERA—interim reanalysis from ECMWF (European Centre for Medium-Range Weather Forecasts) and present the vertical profile of biases for both wind component in winter at high latitude. The biases and the standard deviation obtained increase with altitude

    On the dynamical evolution of the polar stratosphere after the vortex breakdown

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    International audienceThe polar stratosphere remains largely unexplored in the summertime compared to polar winter ozone depletion issues. Several significant gaps remain regarding the knowledge of the dynamical state and of the chemical composition characterizing the polar summer stratosphere and the ability of models to simulate properly the involved mechanisms. During spring after the vortex breakdown large scale transport seems to be responsible of mixing of poor ozone polar air masses and rich ozone air masses from lower latitudes. In addition previous studies based on satellite measurements revealed residual polar vortex air to be located in the arctic stratosphere until at least mid-July. It has been identified also structure named the"frozen-in" anticyclones (FrIAC's) in polar region coming from the tropics as well. However at the moment models are not able to reproduce until July such structures observed. In the frame of the International Polar Year the STRAPOLETE protect has started on January 2009 to study the Arctic stratosphere in the summertime. In this context we study in detail past year 2005 from March (when the vortex breakdown) to July in order to evaluate the ability of dynamical model to represent large scale transport and mixing processes occurring during springtime. We present a detailed study based on a contour advection model. Using potential vorticity (PV) we performed several tests to evaluate qualitatively its ability to represent such dynamical structures (vortex remnants, FrIAC's) until July. Then by a coupling with N2O measurements from MLS (Microwave limb sounder on AURA satellite) instrument we evaluate quantitatively the ability of the model to represent mixing processes. Several sensitivity tests will be presented on the grid resolution and on the diffusion coefficient used. In addition, we performed climatology from year 2002 to 2009 based on PV and MLS measurements on the dynamical evolution of the stratosphere after the vortex breakdown. This climatology will be used to investigate the link between the dynamical structures observed occurrence and the atmospheric waves

    Impact of Streamer Associated with Blue Jets on Stratospheric Ozone: a Model Study

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    International audienceIn the framework of the preparation of TARANIS space mission dedicated to the study of transient luminous events (TLEs), a detailed ion-neutral chemistry model has been developed to simulate the impact of blue jet streamers on stratospheric chemistry. It is based on the MIPLASMO model (Microphysical and Photochemical Lagrangian Model of Ozone) widely used over the last 20 years to interpret balloon and satellite measurements associated with stratospheric ozone. It considers the time evolution of 118 species including neutral and ions species, through a set of 1760 reactions. In addition, the neutral chemistry associated with ozone takes classical nitrogen, chlorine and bromine species into account. After model validation, we focus on the streamer representation in the model. We consider two streamer parametrizations, (i) an electric field pulse with constant value as a function of time during the event, (ii) a time-varying realistic electric field, which is the result of an electrodynamic streamer model. Simulations are performed from 20 km to 50 km altitude. Results obtained are analyzed in two different ways: (i) during the first 100 s to identify the major fast mechanism associated with excited species, (ii) during 2 days to evaluate the impact on neutral chemistry (ozone and NOx species). The modelling results indicate that the time evolution of both excited and neutral species volume mixing ratio are very sensitive to the considered streamer parametrization (pulse or realistic streamer) and the differences for two-day simulations are significant. We particularly focus on ozone loss in the mid-, high-stratosphere and ozone production in the low stratosphere as a function of altitude. We find that the impact of streamer parametrization on ozone depends on the altitude
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