[Show abstract][Hide abstract] ABSTRACT: The Odin satellite carries two instruments capable of determining stratospheric ozone profiles by limb sounding: the Sub-Millimetre Radiometer (SMR) and the UV-visible spectrograph of the OSIRIS (Optical Spectrograph and InfraRed Imager System) instrument. A large number of ozone profiles measurements were performed during six years from November 2001 to present. This ozone dataset is here used to make quantitative comparisons with satellite measurements in order to assess the quality of the Odin/SMR ozone measurements. In a first step, we compare Swedish SMR retrievals version 2.1, French SMR ozone retrievals version 222 (both from the 501.8 GHz band), and the OSIRIS retrievals version 3.0, with the operational version 4.0 ozone product from POAM III (Polar Ozone Atmospheric Measurement). In a second step, we refine the Odin/SMR validation by comparisons with ground-based instruments and balloon-borne observations. We use observations carried out within the framework of the Network for Detection of Atmospheric Composition Change (NDACC) and balloon flight missions conducted by the Canadian Space Agency (CSA), the Laboratoire de Physique et de Chimie de l'Environnement (LPCE, Orléans, France), and the Service d'Aéronomie (SA, Paris, France). Coincidence criteria were 5° in latitude x in 10° longitude, and 5 h in time in Odin/POAM III comparisons, 12 h in Odin/NDACC comparisons, and 72 h in Odin/balloons comparisons. An agreement is found with the POAM III experiment (10–60 km) within −0.3±0.2 ppmv (bias±standard deviation) for SMR (v222, v2.1) and within −0.5±0.2 ppmv for OSIRIS (v3.0). Odin ozone mixing ratio products are systematically slightly lower than the POAM III data and show an ozone maximum lower by 1–5 km in altitude. The comparisons with the NDACC data (10–34 km for ozonesonde, 10–50 km for lidar, 10–60 for microwave instruments) yield a good agreement within −0.15±0.3 ppmv for the SMR data and −0.3±0.3 ppmv for the OSIRIS data. Finally the comparisons with instruments on large balloons (10–31 km) show a good agreement, within −0.7±1 ppmv.
[Show abstract][Hide abstract] ABSTRACT: Water vapour plays an important role for the chemistry and dynamics of the atmosphere. It is a strong greenhouse gas in the troposphere and contributes to cooling in the stratosphere. As the main source of chemically active HOx radicals, it is linked to many photo-chemical cycles controlling the composition of the middle atmosphere.In order to improve our knowledge of the amount and variability of water in the middle atmosphere, the Sub-Millimetre Radiometer (SMR) on board the Odin satellite, launched in February 2001, observes several thermal emission lines of water vapour in the 486–581 GHz spectral range from the Earth's limb. Bands centred at 488.9 and 490.4 GHz are used to study water vapour and its isotopes, on the basis of four observation days per month. Vertical profiles of , , and HDO are retrieved between roughly 20 and 70 km in the stratosphere and mesosphere. A strong water vapour line at 556.9 GHz is simultaneously measured in a second band, providing information in the mesosphere and lower thermosphere between about 40 and 100 km. Measurements of at 552.0 GHz in monthly intervals complete the picture of middle atmospheric water vapour provided by Odin/SMR.The measurements of the isotope HDO in the 20–70 km altitude range allow to study the isotopic ratio of deuterium in stratospheric water vapour (D/H), potentially supplying information on the origin of stratospheric water vapour: transport of tropospheric air through the tropical tropopause layer (TTL) versus in situ chemical production such as from methane oxidation. The unique measurements of the molecules and containing heavy isotopes of oxygen may provide a crucial test for our understanding of the complex chemical reaction mechanisms controlling the exchange of oxygen between water vapour and ozone.
Planetary and Space Science 06/2007; 55(9-55):1093-1102. DOI:10.1016/j.pss.2006.11.021 · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The airborne submillimeter radiometer (ASUR) was deployed onboard the Falcon research aircraft during the scanning imaging absorption spectrometer for atmospheric cartography (SCIAMACHY) validation and utilization experiment (SCIAVALUE) and the European polar stratospheric cloud and lee wave experiment (EuPLEx) campaigns. A large number of ozone profile measurements were performed over a latitude band spanning from 5°S to 80°N in September 2002 and February/March 2003 during the SCIAVALUE and around the northern polar latitudes in January/February 2003 during the EuPLEx. Both missions amassed an ample microwave ozone profile data set that is used to make quantitative comparisons with satellite measurements in order to assess the quality of the satellite retrievals. In this paper, the ASUR ozone profile measurements are compared with measurements from SCIAMACHY and Michelson interferometer for passive atmospheric sounding (MIPAS) on Environmental Satellite and optical spectrograph and infrared imager system (OSIRIS) and submillimeter radiometer (SMR) on the Odin satellite. The cross comparisons with the criterion that the ASUR measurements are performed within ±1000 km and ±6 hrs of the satellite observations show a good agreement with all the four satellite sensors. The differences in data values are the following: −4 to +8% for ASUR-SCIAMACHY (operational product, v2.1), within ±15% for ASUR-SCIAMACHY (scientific product, v1.62), up to +6% for ASUR-MIPAS (operational product v4.61) and ASUR-MIPAS (scientific product v1-O3-1), up to 17% for ASUR-OSIRIS (v012), and −6 to 17% for ASUR-SMR (v222) between the 20- and 40-km altitude range depending on latitude. Thus, the intercomparisons provide important quantitative information about the quality of the satellite ozone profiles, which has to be considered when using the data for scientific analyses.
Journal of Geophysical Research Atmospheres 05/2007; 112(D9). DOI:10.1029/2006JD007830 · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The long-term evolution of upper stratospheric ozone has been recorded by lidars and microwave radiometers within the ground-based Network for the Detection of Stratospheric Change (NDSC), and by the space-borne Solar Backscatter Ultra-Violet instruments (SBUV), Stratospheric Aerosol and Gas Experiment (SAGE), and Halogen Occultation Experiment (HALOE). Climatological mean differences between these instruments are typically smaller than 5% between 25 and 50 km. Ozone anomaly time series from all instruments, averaged from 35 to 45 km altitude, track each other very well and typically agree within 3 to 5%. SBUV seems to have a slight positive drift against the other instruments. The corresponding 1979 to 1999 period from a transient simulation by the fully coupled MAECHAM4-CHEM chemistry climate model reproduces many features of the observed anomalies. However, in the upper stratosphere the model shows too low ozone values and too negative ozone trends, probably due to an underestimation of methane and a consequent overestimation of ClO. The combination of all observational data sets provides a very consistent picture, with a long-term stability of 2% or better. Upper stratospheric ozone shows three main features: (1) a decline by 10 to 15% since 1980, due to chemical destruction by chlorine; (2) two to three year fluctuations by 5 to 10%, due to the Quasi-Biennial Oscillation (QBO); (3) an 11-year oscillation by about 5%, due to the 11-year solar cycle. The 1979 to 1997 ozone trends are larger at the southern mid-latitude station Lauder (45°S), reaching −8%/decade, compared to only about −6%/decade at Table Mountain (35°N), Haute Provence/Bordeaux (≈45°N), and Hohenpeissenberg/Bern(≈47°N). At Lauder, Hawaii (20°N), Table Mountain, and Haute Provence, ozone residuals after subtraction of QBO- and solar cycle effects have levelled off in recent years, or are even increasing. Assuming a turning point in January 1997, the change of trend is largest at southern mid-latitude Lauder, +11%/decade, compared to +7%/decade at northern mid-latitudes. This points to a beginning recovery of upper stratospheric ozone. However, chlorine levels are still very high and ozone will remain vulnerable. At this point the most northerly mid-latitude station, Hohenpeissenberg/Bern differs from the other stations, and shows much less clear evidence for a beginning recovery, with a change of trend in 1997 by only +3%/decade. In fact, record low upper stratospheric ozone values were observed at Hohenpeissenberg/Bern, and to a lesser degree at Table Mountain and Haute Provence, in the winters 2003/2004 and 2004/2005.
Journal of Geophysical Research Atmospheres 05/2006; 111(D10). DOI:10.1029/2005JD006454 · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Water vapour, a strong greenhouse gas, plays an important role for the
dynamics of the middle atmosphere. As a reservoir of HO_x, it is
also linked to many chemical processes like the natural destruction of
ozone. In order to improve our knowledge of the amount and
variability of water in the middle atmosphere, the Sub-Millimetre
Radiometer (SMR) on board the Odin satellite, launched in February
2001, observes several thermal emission lines of water vapour in the
485-580 GHz spectral range from the Earth's limb. A band around 489 GHz
is used to study water vapour and its isotopes, on the basis of 4
observation days per month. Vertical profiles of H2O-16, H2O-18, and
HDO are retrieved between roughly 20 and 70 km in the stratosphere and
mesosphere. A strong water vapour line at 557 GHz is simultaneously
measured in a second band, providing information in the mesosphere
and lower thermosphere between about 40 and 100 km. Measurements of
H2O-17 at 551 GHz in monthly intervals complete the picture of
middle atmospheric water vapour provided by Odin. The unique and
original measurements of the isotopes HDO, H2O-18, and H2O-17 in the
20-70 km altitude range allow to study the isotopic depletion /
enrichment of water, potentially supplying information on the origin
of stratospheric water vapour: transport of tropospheric air through
the tropical tropopause layer (TTL) vs in-situ chemical production by
methane oxidation. Besides a presentation of the Odin data on middle
atmospheric water vapour, an evaluation by comparison with measurements
from other satellite sensors such as AURA/MLS is anticipated. Odin is a
Swedish-led satellite project funded jointly by Sweden (SNSB),
Canada (CSA), Finland (TEKES) and France (CNES).
[Show abstract][Hide abstract] ABSTRACT: Profile measurements of key constituents relevant to polar
stratospheric chemistry and dynamics such as ozone (O3), nitrous
oxide (N2O), chlorine monoxide (ClO), and nitric acid (HNO3), taken
at high latitudes of the winter hemispheres by the Odin Sub- Millimetre
Radiometer (SMR), are presented. The Odin/SMR instrument, launched in
February 2001, employs 4 tunable single-sideband Schottky-diode
heterodyne receivers in the 485-580 GHz spectral range and a 1
m telescope for passive observations of thermal emissions
originating from the Earth's limb. Spectra are recorded using two
high resolution auto-correlator spectrometers. Atmospheric
measurements are performed in a time sharing mode with astronomical
observations. Profile information is retrieved from the spectral
measurements of a limb scan by inverting the radiative transfer equation
for a non-scattering atmosphere. The characteristics of the recently
reprocessed Odin/SMR stratospheric mode level-2 data (version 2.0) are
discussed. Scientific results are presented focusing on measurements
taken in the polar winter stratosphere of both hemispheres
during the period 2001-2005. The Odin/SMR measurements of nitrous
oxide, chlorine monoxide, nitric acid, and ozone allow to study the
chemical and dynamical evolution of the Arctic and Antarctic vortices by
providing information on chlorine activation, denitrification,
subsidence of vortex air, and on ozone loss.
[Show abstract][Hide abstract] ABSTRACT: The NDACC Newsletter brings recent scientific results that stem from observations made in the Network for the Detection of Atmospheric Composition Change. It also gives information about recent and upcoming meetings, relevant projects, as well as station highlights. The Network changed name to the Network for the Detection of Atmospheric Composition Change in November 2005.
[Show abstract][Hide abstract] ABSTRACT: Remote sensing based on quantitative spectroscopy is a powerful tool for precise measurements of atmospheric trace species concentrations. through the use of characteristic spectral signatures of the different molecular species and their associated vibration-rotation and electronic bands in the microwave, infrared, and UV-visible domains. A reliable retrieval of the concentration profiles requires a good characterisation of measurement and spectral fitting errors. This includes an accurate knowledge of spectroscopic parameters of all transition lines or absorption cross sections of interest since uncertainties lead to systematic retrieval errors.
[Show abstract][Hide abstract] ABSTRACT: This paper presents a comparison of co-located and near simultaneous CO measurements from January to May, 2004 and from the Arctic to southern polar regions using the ACE-FTS, in solar occultation mode, and the Odin/SMR, which measures atmospheric emission. We find that there is excellent agreement between the two instruments at the locations investigated over 4 orders of magnitude from the lower stratosphere to the lower thermosphere. There is also good agreement with the CMAM model simulation from 20 km to 90 km in sub-tropical and tropical latitudes but poorer agreement in the upper stratosphere and lower mesosphere in winter polar regions. For the Arctic in March 2004 this can be attributed, at least partly, to the unique dynamical processes in the stratosphere in the winter of 2003-2004. Clearly CO measurements from these instruments will provide a useful tool for testing model transport from the troposphere to the thermosphere.
Geophysical Research Letters 01/2005; 321(15). DOI:10.1029/2005GL022433 · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We use measurements of chlorine monoxide (ClO) by the SMR instrument onboard the Odin satellite to study the nighttime thermal equilibrium between ClO and its dimer Cl2O2. Observations performed in the polar vortex during the 2002–2003 Arctic winter showed enhanced amounts of nighttime ClO over a wide range of stratospheric temperatures (185 < T < 225 K). Odin/SMR measurements are here compared to three-dimensional model calculations using various published estimations of the Keq equilibrium constant between ClO and Cl2O2. Our results show that the value of Keq currently recommended by JPL (Sander et al., 2003) leads to a large underestimation of the observed nighttime ClO amounts, and that a realistic estimation of Keq must lie between the values determined by Cox and Hayman (1988) and Von Hobe et al. (2005).
Geophysical Research Letters 01/2005; 32(11). DOI:10.1029/2005GL022649 · 4.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In September 2002 the Antarctic polar vortex split in two under the influence of a sudden warming. During this event, the Odin satellite was able to measure both ozone (O3) and chlorine monoxide (ClO), a key constituent responsible for the so-called ``ozone hole'', together with nitrous oxide (N2O), a dynamical tracer, and nitric acid (HNO3) and nitrogen dioxide (NO2), tracers of denitrification. The submillimeter radiometer (SMR) microwave instrument and the Optical Spectrograph and Infrared Imager System (OSIRIS) UV-visible light spectrometer (VIS) and IR instrument on board Odin have sounded the polar vortex during three different periods: before (19-20 September), during (24-25 September), and after (1-2 and 4-5 October) the vortex split. Odin observations coupled with the Reactive Processes Ruling the Ozone Budget in the Stratosphere (REPROBUS) chemical transport model at and above 500 K isentropic surfaces (heights above 18 km) reveal that on 19-20 September the Antarctic vortex was dynamically stable and chemically nominal: denitrified, with a nearly complete chlorine activation, and a 70% O3 loss at 500 K. On 25-26 September the unusual morphology of the vortex is monitored by the N2O observations. The measured ClO decay is consistent with other observations performed in 2002 and in the past. The vortex split episode is followed by a nearly complete deactivation of the ClO radicals on 1-2 October, leading to the end of the chemical O3 loss, while HNO3 and NO2 fields start increasing. This acceleration of the chlorine deactivation results from the warming of the Antarctic vortex in 2002, putting an early end to the polar stratospheric cloud season. The model simulation suggests that the vortex elongation toward regions of strong solar irradiance also favored the rapid reformation of ClONO2. The observed dynamical and chemical evolution of the 2002 polar vortex is qualitatively well reproduced by REPROBUS. Quantitative differences are mainly attributable to the too weak amounts of HNO3 in the model, which do not produce enough NO2 in presence of sunlight to deactivate chlorine as fast as observed by Odin.
Journal of Geophysical Research Atmospheres 01/2005; DOI:10.1029/2004JD005018 · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ozone volume mixing ratio (VMR) profiles are measured by the Michelson Interferometer for passive atmospheric sounding (MIPAS) on ENVISAT. The data sets produced by the science data processor at Institut für Meteorologie und Klimaforschung (IMK), Germany are compared with those obtained by halogen occultation experiment (HALOE) on UARS and by sub-millimetre radiometer (SMR) on ODIN. For the stratospheric measurements taken during September/October 2002, the three instruments show reasonable agreement, with global mean differences within 0.1–0.3 ppmv. The typical zonal mean differences are of 0.4 ppmv for HALOE and 0.6 ppmv for SMR (4–6%) in the ozone VMR peak region at 25–30 km near the equator, though larger differences of 0.8–1 ppmv (8–10%) are also observed in a small latitude–altitude region in the tropic. A positive bias of about 0.2–0.4 ppmv in the MIPAS data in the 35–40 km region has also been found. Further studies are under way to explain these differences.
Advances in Space Research 01/2005; DOI:10.1016/j.asr.2005.03.015 · 1.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Sub-Millimetre Radiometer (SMR) on board the Odin satellite, launched on 20 February 2001, observes key species with respect to stratospheric chemistry and dynamics such as O3, ClO, N2O, and HNO3 using two bands centered at 501.8 and 544.6 GHz. We present the adopted methodology for level 2 processing and the achieved in-orbit measurement capabilities of the SMR radiometer for these species in terms of altitude range, altitude resolution, and measurement precision. The characteristics of the relevant level 2 data versions, namely version 1.2 of the operational processor as well as versions 222 and 223 of the reference code, are discussed and differences are evaluated. An analysis of systematic retrieval errors, resulting from spectroscopic and instrumental uncertainties, is also presented.
Journal of Geophysical Research Atmospheres 01/2005; 110. DOI:10.1029/2004JD005741 · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The Sub-Millimetre Radiometer (Odin/SMR) on board the Odin satellite, launched on 20 February 2001, performs regular measurements of the global distribution of stratospheric nitrous oxide (N2O) using spectral observations of the J = 20 -> 19 rotational transition centered at 502.296 GHz. We present a quality assessment for the retrieved N2O profiles (level 2 product) by comparison with independent balloonborne and aircraftborne validation measurements as well as by cross-comparing with preliminary results from other satellite instruments. An agreement with the airborne validation experiments within 28 ppbv in terms of the root mean square (RMS) deviation is found for all SMR data versions (v222, v223, and v1.2) under investigation. More precisely, the agreement is within 19 ppbv for N2O volume mixing ratios (VMR) lower than 200 ppbv and within 10% for mixing ratios larger than 150 ppbv. Given the uncertainties due to atmospheric variability inherent to such comparisons, these values should be interpreted as upper limits for the systematic error of the Odin/SMR N2O measurements. Odin/SMR N2O mixing ratios are systematically slightly higher than nonvalidated data obtained from the Improved Limb Atmospheric Spectrometer-II (ILAS-II) on board the Advanced Earth Observing Satellite-II (ADEOS-II). Root mean square deviations are generally within 23 ppbv (or 20% for VMR-N2O > 100 ppbv) for versions 222 and 223. The comparison with data obtained from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on the Envisat satellite yields a good agreement within 9-17 ppbv (or 10% for VMR-N2O > 100 ppbv) for the same data versions. Odin/SMR version 1.2 data show somewhat larger RMS deviations and a higher positive bias.
Journal of Geophysical Research Atmospheres 01/2005; 110. DOI:10.1029/2004JD005394 · 3.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ozone mixing ratios observed by the Bordeaux microwave radiometer between 1995 and 2002 in an altitude range 25–75 km show diurnal variations in the mesosphere and seasonal variations in terms of annual and semi-annual oscillations (SAO) in the stratosphere and in the mesosphere. The observations with 10–15 km altitude resolution are presented and compared to photochemical and transport model results.Diurnal ozone variations are analyzed by averaging the years 1995–1997 for four representative months and six altitude levels. The photochemical models show a good agreement with the observations for altitudes higher than 50 km. Seasonal ozone variations mainly appear as an annual cycle in the middle and upper stratosphere and a semi-annual cycle in the mesosphere with amplitude and phase depending on altitude. Higher resolution (2 km) HALOE (halogen occultation experiment) ozone observations show a phase reversal of the SAO between 44 and 64 km. In HALOE data, a tendancy for an opposite water vapour cycle can be identified in the altitude range 40–60 km.Generally, the relative variations at all altitudes are well explained by the transport model (up to 54 km) and the photochemical models. Only a newly developed photochemical model (1-D) with improved time-dependent treatment of water vapour profiles and solar flux manages to reproduce fairly well the absolute values.
[Show abstract][Hide abstract] ABSTRACT: Odin is a Swedish-led satellite project funded jointly by Sweden, Canada, Finland and France. The SubMillimeter Radiometer (SMR) onboard the Odin satellite, launched in February 2001, employs 4 tunable single-sideband Schottky-diode heterodyne receivers in the ˜485-580GHz spectral range. In aeronomy mode, various target bands are dedicated to observations of trace constituents relevant to stratospheric/mesospheric chemistry and dynamics such as O\3, ClO, N\2O, HNO\3, H\2O, CO, NO, as well as isotopes of H\2O and O\3. The global distribution of water vapor isotopes and its seasonal variation were obtained for the first time by Odin/SMR measurements. The delta D of water vapor in the stratosphere agrees with the past measurements and a model. It increases with altitude from the TTL to the top of stratospehre. The methane contribution to the increase of delta D is discussed ans the delta D at the overhead of the TTL was estimated.
[Show abstract][Hide abstract] ABSTRACT: A ground-based microwave radiometer dedicated to chlorine monoxide (ClO) measurements around 278GHz has been in operation from December 1993-June 1996 at the Plateau de Bure, France (45° N, 5.9° E, 2500m altitude). It belongs to the international Network for the Detection of Stratospheric Change. A detailed study of both measurements and retrieval schemes has been undertaken. Although dedicated to the measurements of ClO, simultaneous profiles of O<sub>3</sub>, ClO and NO<sub>2</sub>, together with information about the instrumental baseline, have been retrieved using the optimal estimation method. The vertical profiles have been compared with other ground-based microwave data, satellite-borne data and model results. Data quality shows: 1) the weak sensitivity of the instrument that obliges to make time averages over several hours; 2) the site location where measurements of good opacities are possible for only a few days per year; 3) the baseline undulation affecting all the spectra, an issue common to all the microwave instruments; 4) the slow drift of some components affecting frequencies by 3-4MHz within a couple of months. Nevertheless, when temporally averaging data over a few days, ClO temporal variations (diurnal and over several weeks in winter 1995) from 35-50km are consistent with model results and satellite data, particularly at the peak altitude around 40km, although temporal coincidences are infrequent in winter 1995. In addition to ClO, it is possible to obtain O<sub>3</sub> information from 30-60km whilst the instrument is not optimized at all for this molecule. Retrievals of O<sub>3</sub> are reasonable when compared with model and another ground-based data set, although the lowermost layers are affected by the contamination of baseline remnants. Monthly-averaged diurnal variations of NO<sub>2</sub> are detected at 40km and appear in agreement with photochemical model results and satellite zonally-averaged data, although the amplitude is weaker than the other data sets. This NO<sub>2</sub> result highlights the great potential of the retrieval scheme used.
[Show abstract][Hide abstract] ABSTRACT: The optical spectrograph and infrared imager system (OSIRIS) on board the Odin spacecraft is designed to retrieve altitude profiles of terrestrial atmospheric minor species by observing limb-radiance profiles. The grating optical spectrograph (OS) obtains spectra of scattered sunlight over the range 280-800 nm with a spectral resolution of approximately 1 nm. The Odin spacecraft performs a repetitive vertical limb scan to sweep the OS 1 km vertical field of view over selected altitude ranges from approximately 10 to 100 km. The terrestrial absorption features that are superimposed on the scattered solar spectrum are monitored to derive the minor species altitude profiles. The spectrograph also detects the airglow, which can be used to study the mesosphere and lower thermosphere. The other part of OSIRIS is a three-channel infrared imager (IRI) that uses linear array detectors to image the vertical limb radiance over an altitude range of approximately 100 km. The IRI observes both scattered sunlight and the airglow emissions from the oxygen infrared atmospheric band at 1.27 mum and the OH (3-1) Meinel band at 1.53 mum. A tomographic inversion technique is used with a series of these vertical images to derive the two-dimensional distribution of the emissions within the orbit plane.
Canadian Journal of Physics 06/2004; 82(6-6):411-422. DOI:10.1139/P04-005 · 0.96 Impact Factor