L. Saavedra de Miguel

Publications (11)22.08 Total impact

• Source

  Available from: Alain Hauchecorne

  Article: Response of tropical stratospheric O$_3$, NO$_2$ and NO$_3$ to the equatorial Quasi-Biennial Oscillation and to temperature as seen from GOMOS/ENVISAT

  A Hauchecorne, J ~L Bertaux, F Dalaudier, P Keckhut, P Lemennais, S Bekki, M Marchand, J ~C Lebrun, E Kyrölä, J Tamminen, V Sofieva, D Fussen, F Vanhellemont, O Fanton D'Andon, G Barrot, L Blanot, T Fehr, L Saavedra de Miguel
  ATMOSPHERIC CHEMISTRY AND PHYSICS 09/2010; 10:8873-8879. · 5.52 Impact Factor
• Article: GOMOS O$_3$, NO$_2$, and NO$_3$ observations in 2002-2008

  E Kyrölä, J Tamminen, V Sofieva, J ~L Bertaux, A Hauchecorne, F Dalaudier, D Fussen, F Vanhellemont, O Fanton D'Andon, G Barrot, M Guirlet, T Fehr, L Saavedra de Miguel
  Atmospheric Chemistry & Physics. 08/2010; 10:7723-7738.
• Source

  Available from: Filip Vanhellemont

  Article: GOMOS data characterisation and error estimation

  Tamminen J, Kyrölä E, V. F. Sofieva, Laine M, Bertaux J.-L, Hauchecorne A, Dalaudier F, Fussen D, Vanhellemont F, Fanton-d&apos, Andon O, Barrot G, Mangin A, Guirlet M, Blanot L, Fehr T, L. Saavedra de Miguel, Fraisse R
  [show abstract] [hide abstract]
  ABSTRACT: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument uses stellar occultation technique for monitoring ozone, other trace gases and aerosols in the stratosphere and mesosphere. The self-calibrating measurement principle of GOMOS together with a relatively simple data retrieval where only minimal use of a priori data is required provides excellent possibilities for long-term monitoring of atmospheric composition. GOMOS uses about 180 of the brightest stars as its light source. Depending on the individual spectral characteristics of the stars, the signal-to-noise ratio of GOMOS varies from star to star, resulting also in varying accuracy of retrieved profiles. We present here an overview of the GOMOS data characterisation and error estimation, including modeling errors, for O3, NO2, NO3, and aerosol profiles. The retrieval error (precision) of night-time measurements in the stratosphere is typically 0.5–4% for ozone, about 10–20% for NO2, 20–40% for NO3 and 2–50% for aerosols. Mesospheric O3, up to 100 km, can be measured with 2–10% precision. The main sources of the modeling error are incompletely corrected scintillation, inaccurate aerosol modeling, uncertainties in cross sections of trace gases and in atmospheric temperature. The sampling resolution of GOMOS varies depending on the measurement geometry. In the data inversion a Tikhonov-type regularization with pre-defined target resolution requirement is applied leading to 2–3 km vertical resolution for ozone and 4 km resolution for other trace gases and aerosols.
  ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2010; · 5.52 Impact Factor
• Source

  Available from: Filip Vanhellemont

  Article: Retrieval of atmospheric parameters from GOMOS data

  Kyrölä E, Tamminen J, Sofieva V, J. L. Bertaux, Hauchecorne A, Dalaudier F, Fussen D, Vanhellemont F, O. Fanton d'Andon, Barrot G, Guirlet M, Mangin A, Blanot L, Fehr T, L. Saavedra de Miguel, Fraisse R
  [show abstract] [hide abstract]
  ABSTRACT: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on board the European Space Agency's ENVISAT satellite measures attenuation of stellar light in occultation geometry. Daytime measurements also record scattered solar light from the atmosphere. The wavelength regions are the ultraviolet-visible band 248–690 nm and two infrared bands at 755–774 nm and at 926–954 nm. From UV-Visible and IR spectra the vertical profiles of O3, NO2, NO3, H2O, O2 and aerosols can be retrieved. In addition there are two 1 kHz photometers at blue 473–527 nm and red 646–698 nm. Photometer data are used to correct spectrometer measurements for scintillations and to retrieve high resolution temperature profiles as well as gravity wave and turbulence parameters. Measurements cover altitude region 5–150 km. Atmospherically valid data are obtained in 15–100 km. In this paper we present an overview of the GOMOS retrieval algorithms for stellar occultation measurements. The low signal-to-noise ratio and the refractive effects due to the point source nature of stars have been important drivers in the development of GOMOS retrieval algorithms. We present first the Level 1b algorithms that are used to correct instrument related disturbances in the spectrometer and photometer measurements The Level 2 algorithms deal with the retrieval of vertical profiles of atmospheric gaseous constituents, aerosols and high resolution temperature. We divide the presentation into correction for refractive effects, high resolution temperature retrieval and spectral/vertical inversion. The paper also includes discussion about the GOMOS algorithm development, expected improvements, access to GOMOS data and alternative retrieval approaches.
  Atmospheric Chemistry and Physics Discussions. 01/2010;
• Source

  Available from: E. Kyrölä

  Article: Response of tropical stratospheric O₃, NO₂ and NO₃ to the equatorial Quasi-Biennial Oscillation and to temperature as seen from GOMOS/ENVISAT

  Hauchecorne A, J. L. Bertaux, Dalaudier F, Keckhut P, Lemennais P, Bekki S, Marchand M, J. C. Lebrun, Kyrölä E, Tamminen J, Sofieva V, Fussen D, Vanhellemont F, O. Fanton d&apos, Andon, Barrot G, Blanot L, Fehr T, L. Saavedra de Miguel
  [show abstract] [hide abstract]
  ABSTRACT: The stellar occultation spectrometer GOMOS (Global Ozone Monitoring by Occultation of Stars) on ESA's Envisat satellite measures vertical profiles O3, NO2 and NO3 with a high long-term stability due to the self-calibrating nature of the technique. More than 6 years of GOMOS data from August 2002 to end 2008 have been analysed to study the inter-annual variation of O3, NO2 and NO3 in the tropics. It is shown that the QBO of the equatorial wind induces variations in the local concentration larger than 10% for O3 and larger than 25% for NO2. Quasi-Biennial Oscillation signals can be found in the evolution of the three constituents up to at least 40 km. We found that NO3 is positively correlated with temperature up to 45 km in the region where it is in chemical equilibrium with O3. Our results confirm the existence of a transition from a dynamical control of O3 below 28 km with O3 correlated with temperature and a chemical/temperature control between 28 and 38 km with O3 anti-correlated with NO2 and temperature. Above 38 km and up to 50 km a different regime is found with O3 and NO2 correlated with each other and anti-correlated with temperature. For the NO2/temperature anti-correlation in the upper stratosphere, our proposed explanation is the modulation of the N2O ascent by the QBO up to 45 km. The oxidation of N2O is the main source of NOy in this altitude region. An enhancement of the ascending motion will cool adiabatically the atmosphere and will increase the amount of N2O concentration available for NOy formation.
  Atmospheric Chemistry and Physics. 01/2010;
• Source

  Available from: Alain Hauchecorne

  Article: Response of tropical stratospheric O₃, NO₂ and NO₃ to the equatorial Quasi-Biennial Oscillation and to temperature as seen from GOMOS/ENVISAT

  Hauchecorne A, J. L. Bertaux, Dalaudier F, Keckhut P, Lemennais P, Bekki S, Marchand M, J. C. Lebrun, Kyrölä E, Tamminen J, Sofieva V, Fussen D, Vanhellemont F, O. Fanton d'Andon, Barrot G, Blanot L, Fehr T, L. Saavedra de Miguel
  [show abstract] [hide abstract]
  ABSTRACT: The stellar occultation spectrometer GOMOS (Global Ozone Monitoring by Occultation of Stars) on ESA's Envisat satellite measures vertical profiles O₃, NO₂ and NO₃ with a high long-term stability due to the self-calibrating nature of the technique. More than 6 years of GOMOS data from August 2002 to end 2008 have been analysed to study the inter-annual variation of O₃, NO₂ and NO₃ in the tropics. It is shown that the QBO of the equatorial wind induces variations in the local concentration larger than 10% for O₃ and larger than 25% for NO₂. Quasi-Biennial Oscillation signals can be found in the evolution of the three constituents up to at least 45 km. We found that NO₃ is positively correlated with temperature up to 40 km in the region where it is in chemical equilibrium with O₃. Above 40 km, NO₃ is no more in equilibrium during night and its concentration is correlated with both O₃ and NO₂. For O₃ and NO₂, our results confirm the existence of a transition from a dynamical control of O₃ below 28 km with O₃ correlated with NO₂ and temperature and a chemical/temperature control between 28 and 38 km with O₃ anti-correlated with NO₂ and temperature. Above 38 km and up to 50 km a regime never described before is found with both O₃ and NO₂ anti-correlated with temperature. For the NO₂/temperature anti-correlation, our proposed explanation is the modulation of the N₂O ascent in the upper stratosphere by the QBO and the modulation of the Brewer-Dobson circulation. The oxidation of N₂O is the main source of NO_y in this altitude region. An enhancement of the ascending motion will cool adiabatically the atmosphere and will increase the amount of N₂O concentration available for NO_y formation.
  Atmospheric Chemistry and Physics Discussions. 01/2010;
• Source

  Available from: Alain Hauchecorne

  Article: Retrieval of atmospheric parameters from GOMOS data

  Kyrölä E, Tamminen J, Sofieva V, J. L. Bertaux, Hauchecorne A, Dalaudier F, Fussen D, Vanhellemont F, O. Fanton d&apos, Andon, Barrot G, Guirlet M, Mangin A, Blanot L, Fehr T, L. Saavedra de Miguel, Fraisse R
  [show abstract] [hide abstract]
  ABSTRACT: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on board the European Space Agency's ENVISAT satellite measures attenuation of stellar light in occultation geometry. Daytime measurements also record scattered solar light from the atmosphere. The wavelength regions are the ultraviolet-visible band 248–690 nm and two infrared bands at 755–774 nm and at 926–954 nm. From UV-Visible and IR spectra the vertical profiles of O3, NO2, NO3, H2O, O2 and aerosols can be retrieved. In addition there are two 1 kHz photometers at blue 473–527 nm and red 646–698 nm. Photometer data are used to correct spectrometer measurements for scintillations and to retrieve high resolution temperature profiles as well as gravity wave and turbulence parameters. Measurements cover altitude region 5–150 km. Atmospherically valid data are obtained in 15–100 km. In this paper we present an overview of the GOMOS retrieval algorithms for stellar occultation measurements. The low signal-to-noise ratio and the refractive effects due to the point source nature of stars have been important drivers in the development of GOMOS retrieval algorithms. We present first the Level 1b algorithms that are used to correct instrument related disturbances in the spectrometer and photometer measurements The Level 2 algorithms deal with the retrieval of vertical profiles of atmospheric gaseous constituents, aerosols and high resolution temperature. We divide the presentation into correction for refractive effects, high resolution temperature retrieval and spectral/vertical inversion. The paper also includes discussion about the GOMOS algorithm development, expected improvements, access to GOMOS data and alternative retrieval approaches.
  ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2010; · 5.52 Impact Factor
• Source

  Available from: E. Kyrölä

  Article: GOMOS O₃, NO₂, and NO₃ observations in 2002–2008

  Kyrölä E, Tamminen J, Sofieva V, J. L. Bertaux, Hauchecorne A, Dalaudier F, Fussen D, Vanhellemont F, O. Fanton d'Andon, Barrot G, Guirlet M, Fehr T, L. Saavedra de Miguel
  [show abstract] [hide abstract]
  ABSTRACT: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument onboard the European Space Agency's ENVISAT satellite measures ozone, NO₂, NO₃, H₂O, O₂, and aerosols using the stellar occultation method. Global coverage, good vertical resolution and the self-calibrating measurement method make GOMOS observations a promising data set for building various climatologies and time series. In this paper we present GOMOS nighttime measurements of ozone, NO₂, and NO₃ during six years 2002–2008. Using zonal averages we show the time evolution of the vertical profiles as a function of latitude. In order to get continuous coverage in time we restrict the latitudinal region to 50° S–50° N. Time development is analysed by fitting constant, annual and semi-annual terms as well as solar and QBO proxies to the daily time series. Ozone data cover the stratosphere, mesosphere and lower thermosphere (MLT). NO₂ and NO₃ data cover the stratosphere. In addition to detailed analysis of profiles we derive total column distributions using the fitted time series. The time-independent constant term is determined with a good accuracy (better than 1%) for all the three gases. The median retrieval accuracy for the annual and semi-annual term varies in the range 5–20%. For ozone the annual terms dominate in the stratosphere giving early winter ozone maxima at mid-latitudes. Above the ozone layer the annual terms change the phase which results in ozone summer maximum up to 80 km. In the MLT the annual terms dominate up to 80 km where the semiannual terms start to grow. In the equatorial MLT the semi-annual terms dominate the temporal evolution whereas in the mid-latitude MLT annual and semi-annual terms compete evenly. In the equatorial stratosphere the QBO dominates the time development but the solar term is too weak to be determined. In the MLT above 85 km the solar term grows significantly and ozone has 15–20% dependence on the solar cycle. For NO₂ below 32 km the annual summer maxima dominates at mid-latitudes whereas in the equatorial region a strong QBO prevails. In northern mid-latitudes a strong solar term appears in the upper stratosphere. For NO₃ the annual variation dominates giving rise to summer maxima. The NO₃ distribution is controlled by temperature and ozone.
  Atmospheric Chemistry and Physics. 01/2010;
• Source

  Available from: Marko Laine

  Article: Atmospheric Chemistry and Physics GOMOS data characterisation and error estimation

  J Tamminen, E Kyrölä, V F Sofieva, M Laine, J.-L Bertaux, A Hauchecorne, F Dalaudier, D Fussen, F Vanhellemont, O Fanton-D 'andon, G Barrot, A Mangin, M Guirlet, L Blanot, T Fehr, L Saavedra De Miguel, R Fraisse
  [show abstract] [hide abstract]
  ABSTRACT: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument uses stellar occultation tech-nique for monitoring ozone, other trace gases and aerosols in the stratosphere and mesosphere. The self-calibrating mea-surement principle of GOMOS together with a relatively simple data retrieval where only minimal use of a priori data is required provides excellent possibilities for long-term monitoring of atmospheric composition. GOMOS uses about 180 of the brightest stars as its light source. Depending on the individual spectral characteris-tics of the stars, the signal-to-noise ratio of GOMOS varies from star to star, resulting also in varying accuracy of re-trieved profiles. We present here an overview of the GOMOS data characterisation and error estimation, including model-ing errors, for O 3 , NO 2 , NO 3 and aerosol profiles. The re-trieval error (precision) of night-time measurements in the stratosphere is typically 0.5–4% for ozone, about 10–20% for NO 2 , 20–40% for NO 3 and 2–50% for aerosols. Meso-spheric O 3 , up to 100 km, can be measured with 2–10% precision. The main sources of the modeling error are in-completely corrected scintillation, inaccurate aerosol mod-eling, uncertainties in cross sections of trace gases and in atmospheric temperature. The sampling resolution of GO-MOS varies depending on the measurement geometry. In the data inversion a Tikhonov-type regularization with pre-defined target resolution requirement is applied leading to 2– 3 km vertical resolution for ozone and 4 km resolution for other trace gases and aerosols.
  ATMOSPHERIC CHEMISTRY AND PHYSICS 01/2010; 10:9505-9519. · 5.52 Impact Factor
• Article: Cyclone Tracking With Ers-2 Scatterometer:

  P. Lecomte, R. Crapolicchio, L. Saavedra De Miguel
  [show abstract] [hide abstract]
  ABSTRACT: Every year, Tropical Cyclones (TC) produce important damages on a high number of countries: the floods caused for the heavy rain, strong winds and bad sea conditions are producing human and economic losses. Satellite data can help the scientific comunity to study these events. In particular the processing of the backscattering measurements acquired over the ocean is giving important information on the wind field at sea level. The knowledge of the TC wind field structure can help the scientific community to better understand and better forecast these events. To meet the needs of the scientific community, the Product Control Service (PCS) at ESRIN has developed a post-processing procedure for the fast delivery (FD) products processed from the data acquired with the C-band Scatterometer (Scat) flown onboard the ERS satellites. The major skills of this post-processing are: the detection of a TC, the quality improvement of the retrieved wind field and the availability on a web in near "real-time"of a report about this TC and the corresponding reprocessed Scat FD products.
  12/2001;
• Source

  Available from: Filip Vanhellemont

  Article: GOMOS data characterization and error estimation

  J. Tamminen, E. Kyrölä, V. F. Sofieva, M. Laine, Jean-Loup Bertaux, Alain Hauchecorne, Francis Dalaudier, D. Fussen, F. Vanhellemont, O. Fanton d'Andon, G. Barrot, A. Mangin, M. Guirlet, L. Blanot, T. Fehr, L. Saavedra de Miguel, R. Fraisse
  [show abstract] [hide abstract]
  ABSTRACT: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument uses stellar occultation technique for monitoring ozone and other trace gases in the stratosphere and mesosphere. The self-calibrating measurement principle of GOMOS together with a relatively simple data retrieval where only minimal use of a priori data is required, provides excellent possibilities for long term monitoring of atmospheric composition. GOMOS uses about 180 brightest stars as the light source. Depending on the individual spectral characteristics of the stars, the signal-to-noise ratio of GOMOS is changing from star to star, resulting also varying accuracy to the retrieved profiles. We present the overview of the GOMOS data characterization and error estimation, including modeling errors, for ozone, NO2, NO3 and aerosol profiles. The retrieval error (precision) of the night time measurements in the stratosphere is typically 0.5–4% for ozone, about 10–20% for NO2, 20–40% for NO3 and 2–50% for aerosols. Mesospheric O3, up to 100 km, can be measured with 2–10% precision. The main sources of the modeling error are the incompletely corrected atmospheric turbulence causing scintillation, inaccurate aerosol modeling, uncertainties in cross sections of the trace gases and in the atmospheric temperature. The sampling resolution of GOMOS varies depending on the measurement geometry. In the data inversion a Tikhonov-type regularization with pre-defined target resolution requirement is applied leading to 2–3 km resolution for ozone and 4 km resolution for other trace gases.
  Atmospheric Chemistry and Physics.