The Sub‐Millimetre Radiometer (SMR) aboard the Odin satellite has been measuring vertical profiles of atmospheric trace gases since August 2001. We present the inversion methodology developed for CO ...measurements and the first retrieval results. CO can be retrieved from a single scan measurement throughout the middle atmosphere, with a typical resolution of ∼3 km and a relative error of ∼10% to ∼25%. Retrieval results are evaluated through comparison with data from the Whole Atmosphere Community Climate Model (WACCM) and observations of the Improved Stratospheric and Mesospheric Sounder (ISAMS) on board the Upper Atmospheric Research Satellite (UARS). Considering the large natural variability of CO, the SMR retrievals give good confirmation of the WACCM results, with an overall agreement within a factor of 2. ISAMS abundances are higher than SMR mixing ratios by a factor of 5–10 above 0.5 hPa from ∼80°S to ∼50°N.
The mechanisms of transport on annual, semi-annual and quasi-biennial time scales in the equatorial (10° S–10° N) stratosphere are investigated using the nitrous oxide (N2O) measurements of the ...space-borne ODIN Sub-Millimetre Radiometer from November 2001 to June 2005, and the simulations of the three-dimensional chemical transport models MOCAGE and SLIMCAT. Both models are forced with analyses from the European Centre for Medium-range Weather Forecast, but the vertical transport is derived either from the forcing analyses by solving the continuity equation (MOCAGE), or from diabatic heating rates using a radiation scheme (SLIMCAT). The N2O variations in the mid-to-upper stratosphere at levels above 32 hPa are generally well captured by the models though significant differences appear with the observations as well as between the models, attributed to the difficulty of capturing correctly the slow upwelling associated with the Brewer-Dobson circulation. However, in the lower stratosphere, below 32 hPa, the observed variations are shown to be mainly seasonal with peak amplitude at 400–450 K (~17.5–19 km), totally missed by the models. The minimum N2O in June, out of phase by two months with the known minimum seasonal upwelling associated with the Brewer-Dobson circulation and moreover amplified over the Western Pacific compared to Africa is incompatible with the seasonal change of upwelling evoked to explain the O3 annual cycle in the same altitude range (Randel et al., 2007). Unless the 1.5 ppbv amplitude of N2O annual cycle in the upper troposphere is totally wrong, the explanation of the observed N2O annual cycle of 15 ppbv in the lower stratosphere requires another mechanism. A possible candidate for that might be the existence of a downward time-averaged mass flux above specific regions, as shown by Sherwood (2000) over Indonesia, required for compensating the energy sink resulting from the deep overshooting of cold and heavy air at high altitude over intense convective areas. But, since global models do currently not capture this subsidence, it must be recognised that a full explanation of the observations cannot be provided for the moment. However, the coincidence of the peak contrast between the Western Pacific and Africa with the maximum overshooting volume in May reported by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar, suggests a strong influence of deep convection on the chemical composition of the tropical lower stratosphere up to 500 K (21 km).
We present profile measurements of key constituents relevant to stratospheric chemistry and dynamics such as ozone (O3), nitrous oxide (N2O), and chlorine monoxide (ClO) taken during the 2002–03 ...northern hemisphere winter by the Odin Sub‐Millimetre Radiometer (SMR), a limb‐sounding satellite sensor launched in February 2001. The observations of the chemically passive tracer N2O show a subsidence of lower stratospheric air masses inside the Arctic vortex in the range of 3–5 km, or 60–100 K in terms of potential temperature, for the period November 2002 to March 2003. Activated chlorine in the form of ClO was observed inside the vortex from the beginning of December until mid‐February. The accumulated chemical ozone loss over this period, derived from the correlation of ozone with N2O, is estimated to be 28 ± 9% on the 50 ppbv level of N2O, i.e., for lower stratospheric air masses subsiding from ∼23 down to 19 km, the lower limit of the Odin/SMR ozone measurement in the 501.8 GHz band.
A method for assimilating observations of long‐lived species such as ozone (O3) and nitrous oxide (N2O) in a three‐dimensional chemistry transport model (3D‐CTM) is described. The model is forced by ...the temperature and wind analyses from the European Centre for Medium‐Range Weather Forecasts (ECMWF). The O3 and N2O fields used in this study are obtained from the Sub‐Millimeter Radiometer (SMR) aboard the Odin satellite. The assimilation technique used is the sequential statistical interpolation approach. The parametrization of the error covariance matrix of the model forecast field is described. A sensitivity study of the system parameters is done in terms of the OMF (observation minus forecast) vector also called “innovation” vector and in terms of the χ2 (chi‐square) test. The effect of the correlation distances is critical for the assimilated field. The RMS (root mean square) of the OMF for the correlation distances is minimal for values of 1500 km in the meridional direction and 500 km in the zonal direction for both O3 and N2O. The treatment of the meridional distance as a function of latitude does not reveal an important improvement. The χ2 diagnostic shows that the asymptotic value of the model error (the model error of saturation) is optimal for the value of 12.5% for O3 and 18% for N2O. We demonstrate the applicability of the developed assimilation method for the Odin/SMR data. We also present first results of the assimilation of Odin/SMR ozone and nitrous oxide for the period from 22 December 2001 to 17 January 2002.
We present an Observing System Simulation Experiment (OSSE) dedicated to the evaluation of the added value of the Sentinel-4 and Sentinel-5P missions for tropospheric nitrogen dioxide (NO2). ...Sentinel-4 is a geostationary (GEO) mission covering the European continent, providing observations with high temporal resolution (hourly). Sentinel-5P is a low Earth orbit (LEO) mission providing daily observations with a global coverage. The OSSE experiment has been carefully designed, with separate models for the simulation of observations and for the assimilation experiments and with conservative estimates of the total observation uncertainties. In the experiment we simulate Sentinel-4 and Sentinel-5P tropospheric NO2 columns and surface ozone concentrations at 7 by 7 km resolution over Europe for two 3-month summer and winter periods. The synthetic observations are based on a nature run (NR) from a chemistry transport model (MOCAGE) and error estimates using instrument characteristics. We assimilate the simulated observations into a chemistry transport model (LOTOS-EUROS) independent of the NR to evaluate their impact on modelled NO2 tropospheric columns and surface concentrations. The results are compared to an operational system where only ground-based ozone observations are ingested. Both instruments have an added value to analysed NO2 columns and surface values, reflected in decreased biases and improved correlations. The Sentinel-4 NO2 observations with hourly temporal resolution benefit modelled NO2 analyses throughout the entire day where the daily Sentinel-5P NO2 observations have a slightly lower impact that lasts up to 3–6 h after overpass. The evaluated benefits may be even higher in reality as the applied error estimates were shown to be higher than actual errors in the now operational Sentinel-5P NO2 products. We show that an accurate representation of the NO2 profile is crucial for the benefit of the column observations on surface values. The results support the need for having a combination of GEO and LEO missions for NO2 analyses in view of the complementary benefits of hourly temporal resolution (GEO, Sentinel-4) and global coverage (LEO, Sentinel-5P).
Actuellement, les organismes marins constituent une source très importante de nouvelles molécules dans la pharmacologie et ainsi dans le développement de nouveaux produits bioactifs. Des extraits ...organiques et aqueux de deux éponges marines
Cinachyrella tarentine récoltée pendant deux saisons différentes (hiver et été) et
Cliona viridis récoltée dans deux endroits différents sur le littoral d’El Jadida (Maroc) ont été testés pour leur activité antifongique sur des levures de référence impliquées en pathologie humaine, en utilisant la méthode de diffusion en milieu solide. L’éponge
C. tarentine récoltée en hiver présente une activité très importante par rapport à celle récoltée en été. Alors que l’éponge
C. viridis récoltée au large d’El Jadida (zone profonde et non polluée) présente une activité fongique faible par rapport à celle récoltée dans le port de Jorf Lasfar (zone moins profonde et polluée).
Currently, marine organisms have a very important source of new molecules in pharmacology and thus in the development of new bioactive products. The organic and aqueous extracts of two marine sponges,
Cinachyrella tarentine collected during two different seasons, winter and summer, and
Cliona viridis collected in two different zones on the coast of El Jadida (Morocco) were tested for their antifungal activity using the diffusion method. The
C. tarentine sponge collected in January (winter) has a very important activity compared to that collected in August (summer). While the sponge
C. viridis collected from Jorf Lasfar port (shallower and polluted area) has a very important activity compared to that collected from the coast of El Jadida (depth and unpolluted area).
In the framework of the
Chemistry-Aerosol Mediterranean Experiment (ChArMEx;
http://charmex.lsce.ipsl.fr, last access: 22 June 2018) project, we study the evolution of surface ozone over the ...Mediterranean Basin
(MB) with a focus on summertime over the time period 2000–2100, using the
Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)
outputs from 13 models. We consider three different periods (2000, 2030 and
2100) and the four Representative Concentration Pathways (RCP2.6, RCP4.5,
RCP6.0 and RCP8.5) to study the changes in the future ozone and its budget.
We use a statistical approach to compare and discuss the results of the
models. We discuss the behavior of the models that simulate the surface ozone
over the MB. The shape of the annual cycle of surface ozone simulated by
ACCMIP models is similar to the annual cycle of the ozone observations, but
the model values are biased high. For the summer, we found that most of the
models overestimate surface ozone compared to observations over the most
recent period (1990–2010). Compared to the reference period (2000), we found
a net decrease in the ensemble mean surface ozone over the MB in 2030 (2100)
for three RCPs: −14 % (−38 %) for RCP2.6, −9 % (−24 %) for RCP4.5
and −10 % (−29 %) for RCP6.0. The surface ozone decrease over the MB
for these scenarios is much more pronounced than the relative changes of the
global tropospheric ozone burden. This is mainly due to the reduction in
ozone precursors and to the nitrogen oxide (NOx = NO +
NO2)-limited regime over the MB. For RCP8.5, the ensemble mean
surface ozone is almost constant over the MB from 2000 to 2100. We show how
the future climate change and in particular the increase in methane
concentrations can offset the benefits from the reduction in emissions of
ozone precursors over the MB.
The Gradient in Longitude of Atmospheric constituents above the Mediterranean
basin (GLAM) campaign was set up in August 2014, as part of the
Chemistry and Aerosol Mediterranean Experiment (ChArMEx) ...project. This campaign
aimed to study the chemical variability of gaseous pollutants and aerosols
in the troposphere along a west–east transect above the Mediterranean Basin
(MB). In the present work, we focus on two biomass burning events detected at
5.4 and 9.7 km altitude above sea level (a.s.l.) over Sardinia (from
39∘12′ N–9∘15′ E to
35∘35′ N–12∘35′ E and at
39∘30′ N–8∘25′ E, respectively). Concentration
variations in trace gas carbon monoxide (CO), ozone (O3) and aerosols
were measured thanks to the standard instruments on board the Falcon 20
aircraft operated by the Service des Avions Français Instrumentés
pour la Recherche en Environnement (SAFIRE) and the Spectromètre
InfraRouge In situ Toute Altitude (SPIRIT) developed by LPC2E. Twenty-day
backward trajectories with Lagrangian particle dispersion model FLEXPART
(FLEXible PARTicle) help to understand the transport processes and the origin
of the emissions that contributed to this pollution detected above
Sardinia. Biomass burning emissions came (i) on 10 August from the North
American continent with air masses transported during 5 days before arriving
over the MB, and (ii) on 6 August from Siberia, with air masses travelling
during 12 days and enriched in fire emission products above Canada 5 days
before arriving over the MB. In combination with the Global Fire Assimilation
System (GFAS) inventory and the Moderate Resolution Imaging Spectroradiometer
(MODIS) satellite fire locations, FLEXPART reproduces well the contribution
of those fires to CO and aerosols enhancements under adjustments of the
injection height to 10 km in both cases and application of an amplification
factor of 2 on CO GFAS emissions for the 10 August event. The chemistry
transport model (CTM) MOCAGE is used as a complementary tool for the case of
6 August to confirm the origin of the emissions by tracing the CO global
atmospheric composition reaching the MB. For this event, both models agree on
the origin of air masses with CO concentrations simulated with MOCAGE lower
than the observed ones, likely caused by the coarse model horizontal
resolution that yields the dilution of the emissions and diffusion during
transport. In combination with wind fields, the analysis of the transport of
the air mass documented on 6 August suggests the subsidence of CO pollution
from Siberia towards North America and then a transport to the MB via fast
jet winds located at around 5.5 km in altitude. Finally, using the ratio
ΔO3 ∕ ΔCO, the plume age can be estimated and the
production of O3 during the transport of the air mass is studied using
the MOCAGE model.
Numerical dispersion models are used operationally worldwide to mitigate the effect of volcanic ash on aviation. In order to improve the representation of the horizontal dispersion of ash plumes and ...of the 3D concentration of ash, a study was conducted using the MOCAGE model during the European Natural Airborne Disaster Information and Coordination System for Aviation (EUNADICS-AV) project. Source term modelling and assimilation of different data were investigated. A sensitivity study of source term formulation showed that a resolved source term, using the FPLUME plume rise model in MOCAGE, instead of a parameterised source term, induces a more realistic representation of the horizontal dispersion of the ash plume. The FPLUME simulation provides more concentrated and focused ash concentrations in the horizontal and the vertical dimensions than the other source term. The assimilation of Moderate Resolution Imaging Spectroradiometer (MODIS) aerosol optical depth has an impact on the horizontal dispersion of the plume, but this effect is rather low and local compared to source term improvement. More promising results are obtained with the continuous assimilation of ground-based lidar profiles, which improves the vertical distribution of ash and helps in reaching realistic values of ash concentrations. Using this configuration, the effect of assimilation may last for several hours and it may propagate several hundred kilometres downstream of the lidar profiles.
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