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First climatology of polar mesospheric clouds from GOMOS/ENVISAT stellar occultation instrument
K. Pérot, A. Hauchecorne, F. Montmessin, J.-L. Bertaux, L. Blanot, F. Dalaudier, D. Fussen,E. Kyr l
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2010,
Abstract: GOMOS (Global Ozone Monitoring by Occultation of Stars), on board the European platform ENVISAT launched in 2002, is a stellar occultation instrument combining four spectrometers and two fast photometers which measure light at 1 kHz sampling rate in the two visible channels 470–520 nm and 650–700 nm. On the day side, GOMOS does not measure only the light from the star, but also the solar light scattered by the atmospheric molecules. In the summer polar days, Polar Mesospheric Clouds (PMC) are clearly detected using the photometers signals, as the solar light scattered by the cloud particles in the instrument field of view. The sun-synchronous orbit of ENVISAT allows observing PMC in both hemispheres and the stellar occultation technique ensures a very good geometrical registration. Four years of data, from 2002 to 2006, are analyzed up to now. GOMOS data set consists of approximately 10 000 cloud observations all over the eight PMC seasons studied. The first climatology obtained by the analysis of this data set is presented, focusing on the seasonal and latitudinal coverage, represented by global maps. GOMOS photometers allow a very sensitive PMC detection, showing a frequency of occurrence of 100% in polar regions during the middle of the PMC season. According to this work mesospheric clouds seem to be more frequent in the Northern Hemisphere than in the Southern Hemisphere. The PMC altitude distribution was also calculated. The obtained median values are 82.7 km in the North and 83.2 km in the South.
First climatology of polar mesospheric clouds from GOMOS/ENVISAT stellar occultation instrument  [PDF]
K. Pérot,A. Hauchecorne,F. Montmessin,J.-L. Bertaux
Atmospheric Chemistry and Physics Discussions , 2009,
Abstract: GOMOS (Global Ozone Monitoring by Occultation of Stars), on board the European platform ENVISAT launched in 2002, is a stellar occultation instrument combining four spectrometers and two fast photometers which measure light at 1 kHz sampling rate in the two visible channels 470–520 nm and 650–700 nm. On the day side, GOMOS does not measure only the light from the star, but also the solar light scattered by the atmospheric molecules. In the summer polar days, Polar Mesospheric Clouds (PMC) are clearly detected using the photometers signals, as the solar light scattered by the cloud particles in the instrument field of view. The sun-synchronous orbit of ENVISAT allows observing PMC in both hemispheres and the stellar occultation technique ensures a very good geometrical registration. Four years of data, from 2002 to 2006, are analyzed up to now. GOMOS data set consists of approximately 10 000 cloud observations all over the eight PMC seasons studied. The first climatology obtained by the analysis of this data set is presented, focusing on the seasonal and latitudinal coverage, represented by global maps. GOMOS photometers allow a very sensitive PMC detection, showing a frequency of occurrence of 100% in polar regions during the middle of the PMC season. According to this work mesospheric clouds seem to be more frequent in the Northern Hemisphere than in the Southern Hemisphere. The PMC altitude distribution was also calculated. The obtained median values are 82.7 km in the North and 83.2 km in the South.
Global ozone monitoring by occultation of stars: an overview of GOMOS measurements on ENVISAT
J. L. Bertaux, E. Kyr l , D. Fussen, A. Hauchecorne, F. Dalaudier, V. Sofieva, J. Tamminen, F. Vanhellemont, O. Fanton d'Andon, G. Barrot, A. Mangin, L. Blanot, J. C. Lebrun, K. Pérot, T. Fehr, L. Saavedra, G. W. Leppelmeier,R. Fraisse
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2010,
Abstract: GOMOS on ENVISAT (launched in February, 2002) is the first space instrument dedicated to the study of the atmosphere of the Earth by the technique of stellar occultations (Global Ozone Monitoring by Occultation of Stars). Its polar orbit makes good latitude coverage possible. Because it is self-calibrating, it is particularly well adapted to long time trend monitoring of stratospheric species. With 4 spectrometers, the wavelength coverage of 248 nm to 942 nm enables monitoring ozone, H2O, NO2, NO3, air density, aerosol extinction, and O2. Two additional fast photometers (with 1 kHz sampling rate) enable the correction of the effects of scintillations, as well as the study of the structure of air density irregularities resulting from gravity waves and turbulence. A high vertical resolution profile of the temperature may also be obtained from the time delay between the red and the blue photometer. Noctilucent clouds (Polar Mesospheric Clouds, PMC) are routinely observed in both polar summers and global observations of OClO and sodium are achieved. The instrument configuration, dictated by the scientific objectives' rationale and technical constraints, is described, together with the typical operations along one orbit, along with the statistics from over 6 years of operation. Typical atmospheric transmission spectra are presented and some retrieval difficulties are discussed, in particular for O2 and H2O. An overview is presented of a number of scientific results already published or found in more detail as companion papers in the same ACP GOMOS special issue. This paper is particularly intended to provide an incentive for the exploitation of GOMOS data available to the whole scientific community in the ESA data archive, and to help GOMOS data users to better understand the instrument, its capabilities and the quality of its measurements, thus leading to an increase in the scientific return.
Global ozone monitoring by occultation of stars: an overview of GOMOS measurements on ENVISAT  [PDF]
J. L. Bertaux,E. Kyr?l?,D. Fussen,A. Hauchecorne
Atmospheric Chemistry and Physics Discussions , 2010, DOI: 10.5194/acpd-10-9917-2010
Abstract: GOMOS on ENVISAT (launched in February, 2002) is the first space instrument dedicated to the study of the atmosphere of the Earth by the technique of stellar occultations (Global Ozone Monitoring by Occultation of Stars). From a polar orbit, it allows to have a good latitude coverage. Because it is self-calibrated, it is particularly well adapted to the long time trend monitoring of stratospheric species. With 4 spectrometers the wavelength coverage of 248 nm to 942 nm allows to monitor ozone, H2O, NO2, NO3, air, aerosols, and O2. Two additional fast photometers (1 kHz sampling rate) allow for the correction of scintillations, as well as the study of the structure of air density irregularities, resulting from gravity waves and turbulence. A high vertical resolution profile of the temperature may also be obtained from the time delay between the red and the blue photometer. Noctilucent clouds (Polar Mesospheric Clouds, PMC), are routinely observed in both polar summers, and global observations of OCLO and sodium are achieved. The instrument configuration, dictated by the scientific objectives rationale and technical constraints, are described, together with the typical operations along one orbit, and statistics over 5 years of operation. Typical atmospheric transmission spectra are presented, and some retrieval difficulties are discussed, in particular for O2 and H2O. An overview of a number of scientific results is presented, already published or found in more details as companion papers in the same ACP GOMOS special issue. This paper is particularly intended to provide the incentive for GOMOS data exploitation, available to the whole scientific community in the ESA data archive, and to help the GOMOS data users to better understand the instrument, its capabilities and the quality of its measurements, for an optimized scientific return.
A 2003 stratospheric aerosol extinction and PSC climatology from GOMOS measurements on Envisat  [PDF]
F. Vanhellemont,D. Fussen,C. Bingen,E. Kyr?l?
Atmospheric Chemistry and Physics Discussions , 2005,
Abstract: Stratospheric aerosols play an important role in a number of atmospheric issues such as midlatitude ozone depletion, atmospheric dynamics and the Earth radiative budget. Polar stratospheric clouds on the other hand are a crucial factor in the yearly Arctic 5 and Antarctic ozone depletion. It is therefore important to quantify the stratospheric aerosol/PSC abundance. In orbit since March 2002, the GOMOS instrument onboard the European Envisat satellite has provided a vast aerosol extinction data set. In this paper we present an aerosol/PSC climatology that was constructed from this data set, together with a discussion of the results.
A global climatology of stratospheric OClO derived from GOMOS measurement  [PDF]
C. Tétard,D. Fussen,F. Vanhellemont,C. Bingen
Atmospheric Measurement Techniques Discussions , 2013, DOI: 10.5194/amtd-6-3511-2013
Abstract: The Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument on board the European platform ENVISAT was dedicated to the study of the atmosphere of the Earth using the stellar occultation technique. The spectral range of the GOMOS spectrometer extends from the UV to the near infrared, allowing for the retrieval of species such as O3, NO2, NO3, H2O, O2, air density, aerosol extinction and OClO. Nevertheless, OClO can not be retrieved using a single GOMOS measurement because of the weak signal-to-noise ratio and the small optical thickness associated with this molecule. We present here the method used to detect this molecule by using several GOMOS measurements. It is based on a two-step approach. First, several co-located measurements are combined in a statistical way to build an averaged measurement with a higher signal-to-noise ratio. Then, a Differential Optical Absorption Spectroscopy (DOAS) method is applied to retrieve OClO slant column densities. The statistics of the sets of GOMOS measurements used to build the averaged measurement and the spectral window selection are analyzed. The obtained retrievals are compared to results from two balloon-borne instruments. It appears that the inter-comparisons of OClO are generally satisfying. Then, two nighttime climatologies of OClO slant column densities based on GOMOS averaged measurements are presented. The first depicts annual global pictures of OClO from 2003 to 2011. From this climatology, the presence of an OClO layer in the equatorial region at about 35 km is confirmed and strong concentrations of OClO in both polar regions are observed, a sign of chlorine activation. The second climatology is a monthly time series. It clearly shows the chlorine activation of the lower stratosphere during winter. Moreover the equatorial OClO layer is observed during all the years without any significant variations. Finally, the anti-correlation between OClO and NO2 is highlighted. This very promising method, applied on GOMOS measurements, allowed us to build the first nighttime climatology of OClO.
Magnetometry with Mesospheric Sodium  [PDF]
J. M. Higbie,S. M. Rochester,B. Patton,R. Holzl?hner,D. Bonaccini Calia,D. Budker
Physics , 2009,
Abstract: Measurement of magnetic fields on the few-hundred-kilometer length scale is significant for a variety of geophysical applications including mapping of crustal magnetism and ocean-circulation measurements, yet available techniques for such measurements are very expensive or of limited accuracy. We propose a scheme for remote detection of magnetic fields using the naturally occurring atomic-sodium-rich layer in the mesosphere and existing high-power lasers developed for laser guide-star applications. The proposed scheme offers dramatic reduction in cost, opening the way to large-scale magnetic mapping missions.
A 2003 stratospheric aerosol extinction and PSC climatology from GOMOS measurements on Envisat
F. Vanhellemont, D. Fussen, C. Bingen, E. Kyr l , J. Tamminen, V. Sofieva, S. Hassinen, P. Verronen, A. Sepp l , J. L. Bertaux, A. Hauchecorne, F. Dalaudier, O. Fanton d'Andon, G. Barrot, A. Mangin, B. Theodore, M. Guirlet, J. B. Renard, R. Fraisse, P. Snoeij, R. Koopman,L. Saavedra
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2005,
Abstract: Stratospheric aerosols play an important role in a number of atmospheric issues such as midlatitude ozone depletion, atmospheric dynamics and the Earth radiative budget. Polar stratospheric clouds on the other hand are a crucial factor in the yearly Arctic and Antarctic ozone depletion. It is therefore important to quantify the stratospheric aerosol/PSC abundance. In orbit since March 2002, the GOMOS instrument onboard the European Envisat satellite has provided a vast aerosol extinction data set. In this paper we present aerosol/PSC zonal median values that were constructed from this data set, together with a discussion of the results.
Satellite measurements of the global mesospheric sodium layer
Z. Y. Fan, J. M. C. Plane, J. Gumbel, J. Stegman,E. J. Llewellyn
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2007,
Abstract: Optimal estimation theory is used to retrieve the absolute Na density profiles in the mesosphere/lower thermosphere from limb-scanning measurements of the Na radiance at 589 nm in the dayglow. Two years of observations (2003 and 2004), recorded by the OSIRIS spectrometer on the Odin satellite, have been analysed to yield the seasonal and latitudinal variation of the Na layer column abundance, peak height, and peak width. The layer shows little seasonal variation at low latitudes, but the winter/summer ratio increases from a factor of ~3 at mid-latitudes to ~10 in the polar regions. Comparison of the measurements made at about 06:00 and 18:00 LT shows little diurnal variation in the layer, apart from the equatorial region where, during the equinoxes, there is a two-fold increase in Na density below 94 km between morning and evening. This is most likely caused by the strong downward wind produced by the diurnal tide between ~02:00 and 10:00 LT. The dramatic removal of Na below 85 km at latitudes above 50° during summer is explained by the uptake of sodium species on the ice surfaces of polar mesospheric clouds, which were simultaneously observed by the Odin satellite.
Satellite measurements of the global mesospheric sodium layer  [PDF]
Z. Y. Fan,J. M. C. Plane,J. Gumbel,J. Stegman
Atmospheric Chemistry and Physics Discussions , 2007,
Abstract: Optimal estimation theory is used to retrieve the absolute Na density profiles in the mesosphere/lower thermosphere from limb-scanning measurements of the Na radiance at 589 nm in the dayglow. Two years of observations (2003 and 2004), recorded by the OSIRIS spectrometer on the Odin satellite, have been analysed to yield the seasonal and latitudinal variation of the Na layer column abundance, peak height, and peak width. The layer shows little seasonal variation at low latitudes, but the winter/summer ratio increases from a factor of ~3 at mid-latitudes to ~10 in the polar regions. Comparison of the measurements made at about 06:00 and 18:00 LT shows little diurnal variation in the layer, apart from the equatorial region where, during the equinoxes, there is a two-fold increase in Na density below 94 km between morning and evening. This is most likely caused by the strong downward wind produced by the diurnal tide between ~02:00 and 10:00 LT. The dramatic removal of Na below 85 km at latitudes above 50° during summer is explained by the uptake of sodium species on the ice surfaces of polar mesospheric clouds, which were simultaneously observed by the Odin satellite.
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