DOCSLIB.ORG

Validation of SCIAMACHY HDO/H2O Measurements Using the TCCON and NDACC-MUSICA Networks

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Validation of SCIAMACHY HDO/H2O Measurements Using the TCCON and NDACC-MUSICA Networks Atmos. Meas. Tech., 8, 1799–1818, 2015 www.atmos-meas-tech.net/8/1799/2015/ doi:10.5194/amt-8-1799-2015 © Author(s) 2015. CC Attribution 3.0 License. Validation of SCIAMACHY HDO=H2O measurements using the TCCON and NDACC-MUSICA networks R. A. Scheepmaker1, C. Frankenberg2, N. M. Deutscher3,4, M. Schneider5,6, S. Barthlott5, T. Blumenstock5, O. E. Garcia6, F. Hase5, N. Jones4, E. Mahieu7, J. Notholt3, V. Velazco4, J. Landgraf1, and I. Aben1 1SRON Netherlands Institute for Space Research, Utrecht, the Netherlands 2Jet Propulsion Laboratory (JPL), California Institute of Technology, Pasadena, CA, USA 3Institute for Environmental Physics, University of Bremen, Bremen, Germany 4Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, Australia 5Karlsruhe Institute of Technology (KIT), Institute for Meteorology and Climate Research (IMK-ASF), Karlsruhe, Germany 6Izaña Atmospheric Research Centre (IARC), Agencia Estatal de Meteorología (AEMET), Santa Cruz de Tenerife, Spain 7Institute of Astrophysics and Geophysics, University of Liège, Liège, Belgium Correspondence to: R. A. Scheepmaker ([email protected]) Received: 20 October 2014 – Published in Atmos. Meas. Tech. Discuss.: 27 November 2014 Revised: 26 March 2015 – Accepted: 27 March 2015 – Published: 21 April 2015 Abstract. Measurements of the atmospheric HDO=H2O ra- ments nor to a strong reduction of the latitudinal dependency tio help us to better understand the hydrological cycle and of the bias. The correction might be an improvement for dry, improve models to correctly simulate tropospheric humid- high-altitude areas, such as the Tibetan Plateau and the An- ity and therefore climate change. We present an updated ver- des region. For these areas, however, validation is currently sion of the column-averaged HDO=H2O ratio data set from impossible due to a lack of ground stations. The mean stan- the SCanning Imaging Absorption spectroMeter for Atmo- dard deviation of single-sounding SCIAMACHY–FTS dif- spheric CHartographY (SCIAMACHY). The data set is ex- ferences is ∼ 115 ‰, which is reduced by a factor ∼ 2 when tended with 2 additional years, now covering 2003–2007, we consider monthly means. When we relax the strict match- and is validated against co-located ground-based total col- ing of individual measurements and focus on the mean sea- umn δD measurements from Fourier transform spectrom- sonalities using all available FTS data, we find that the corre- eters (FTS) of the Total Carbon Column Observing Net- lation coefficients between SCIAMACHY and the FTS net- work (TCCON) and the Network for the Detection of At- works improve from 0.2 to 0.7–0.8. Certain ground stations mospheric Composition Change (NDACC, produced within show a clear asymmetry in δD during the transition from the the framework of the MUSICA project). Even though the dry to the wet season and back, which is also detected by time overlap among the available data is not yet ideal, we SCIAMACHY. This asymmetry points to a transition in the determined a mean negative bias in SCIAMACHY δD of source region temperature or location of the water vapour −35 ± 30 ‰ compared to TCCON and −69 ± 15 ‰ com- and shows the added information that HDO=H2O measure- pared to MUSICA (the uncertainty indicating the station- ments provide when used in combination with variations in to-station standard deviation). The bias shows a latitudinal humidity. dependency, being largest (∼ −60 to −80 ‰) at the high- est latitudes and smallest (∼ −20 to −30 ‰) at the lowest latitudes. We have tested the impact of an offset correction to the SCIAMACHY HDO and H2O columns. This correc- 1 Introduction tion leads to a humidity- and latitude-dependent shift in δD and an improvement of the bias by 27 ‰, although it does The hydrological cycle plays a key role in the uncertainty of not lead to an improved correlation with the FTS measure- climate change. More specifically, water vapour plays an im- portant role, since it is the strongest natural greenhouse gas. Published by Copernicus Publications on behalf of the European Geosciences Union. 1800 R. A. Scheepmaker et al.: Validation of SCIAMACHY HDO=H2O measurements Water vapour is involved in positive feedback mechanisms curacy but only for about 20–30 locations (and often less (Soden et al., 2005; Randall et al., 2007) as well as in cloud for older periods of coinciding satellite measurements). First formation processes of which the feedback mechanisms are comparisons between measurements of the ratio HDO=H2O still poorly understood (Boucher et al., 2013). Observations in the middle-to-lower troposphere and GCMs have been per- of water vapour isotopologues, such as HDO, can be used to formed and show the great potential for long time series of improve our understanding, as phase changes leave distinct tropospheric HDO=H2O ratio measurements to help in the isotopic signatures in the water vapour (Dansgaard, 1964; improvement of the models and to gain a better understand- Craig and Gordon, 1965). Improving global general circu- ing of the hydrological cycle (Risi et al., 2010, 2012a,b; lation models (GCMs) to correctly capture these signatures Yoshimura et al., 2011). will lead to a better representation of the many interacting With new satellite HDO data sets available, such as from processes that control tropospheric humidity (Jouzel et al., the Greenhouse gases Observing Satellite (GOSAT, Franken- 1987), which will eventually lead to more robust climate pro- berg et al., 2013; Boesch et al., 2013), or currently being de- jections. veloped, such as from the Tropospheric Monitoring Instru- Global satellite measurements, as well as ground-based ment (TROPOMI, Veefkind et al., 2012), long and global Fourier transform spectrometer (FTS) measurements of time series of tropospheric δD are becoming a reality. It HDO have become available in recent years. The measure- is crucial, however, that these data sets are properly vali- ments of HDO are normally expressed as a ratio of the HDO dated to ensure consistency and intercomparability and to 16 abundance to the abundance of the main isotopologue H2 O better identify their potential advantages and shortcomings. (from here on referred to as H2O). We use the standard “delta In this respect it is also important to demonstrate that δD notation” for the fractionation of column-averaged HDO rel- adds information that is not contained in H2O measure- ative to Vienna Standard Mean Ocean Water (VSMOW): ments alone and that the satellite data sets are capable of VCD(HDO)=VCD.H O/ adding this information. A clear example of such activities δD D 2 − 1 × 1000 ‰; (1) is the project MUSICA (MUlti-Platform remote Sensing of R s Isotopologues for investigating the Cycle of Atmospheric in which VCD stands for the vertical column density and water), which consists of a ground-based (NDACC) and a −4 Rs D 3:1152 × 10 is the HDO abundance of VSMOW space-based (IASI) remote sensing component and aims at (Craig, 1961). The bar in the notation δD indicates that it providing quasi-global and homogeneous tropospheric H2O represents a column-averaged value of δD. In the remainder and δD data (Schneider et al., 2012). Recent MUSICA ef- of this work, however, the column averaging is always im- forts include extensive theoretical data characterization, con- plied and we will simply use the notation δD. tinuous in situ measurements, aircraft campaigns and com- Certain measurements directly retrieve δD, as well as the parisons between ground- and space-based data (Schneider separate total columns HDO and H2O, while other measure- et al., 2015; Wiegele et al., 2014). ments retrieve HDO and H2O separately and calculate δD a Here, we present an updated version of the SCIAMACHY posteriori. The first satellite retrievals of HDO (and a poste- δD data set. The European Space Agency’s Environmen- riori calculated δD) were taken by the Interferometric Mon- tal Research Satellite (ENVISAT) mission, with the SCIA- itor for Greenhouse gases (IMG, Zakharov et al., 2004), fol- MACHY instrument on board, ended 8 April 2012. The orig- lowed by the SCanning Imaging Absorption SpectroMeter inal SCIAMACHY δD data set, however, covers the years for Atmospheric CHartographY (SCIAMACHY, Franken- 2003–2005 (Frankenberg et al., 2009). The next available berg et al., 2009). The first direct retrievals of δD were global δD data set, with a high sensitivity in the lower tropo- taken by the Thermal Emission Spectrometer (TES, Worden sphere, is from GOSAT, which started measurements in 2009 et al., 2007), followed by the Infrared Atmospheric Sound- (Frankenberg et al., 2013; Boesch et al., 2013). As a first step ing Interferometer (IASI, Herbin et al., 2009; Schneider and in our effort to acquire longer and overlapping time series Hase, 2011; Lacour et al., 2012; Wiegele et al., 2014). From of δD, including a better data characterization, we have ex- the ground, very precise measurements of atmospheric HDO panded the SCIAMACHY δD time series with 2 additional are obtained with FTS instruments, organized in networks years to cover the period 2003–2007. Although this time se- such as the Total Carbon Column Observing Network (TC- ries is not long enough to reach overlap with GOSAT, it is CON, Wunch et al., 2011, retrieval of HDO and H2O among long enough to allow for sufficient measurements coincid- other trace gases) and the Network for Detection of Atmo- ing with data from ground-based FTS stations to perform a spheric Composition Change (NDACC, formerly the Net- first validation and to study if the measurements of HDO add work for Detection of Stratospheric Change, Kurylo and information to the measurements of H2O alone. Assuming Solomon, 1990, retrieval of δD, HDO and H2O among other the ground-based FTS measurements remain consistent, they trace gases). These different observations greatly comple- could yield a transfer between SCIAMACHY and GOSAT. ment each other, as the satellite measurements have near The updated SCIAMACHY δD data set is introduced in global coverage but at relatively low precision and accuracy, Sect.2, and in Sect.3 we describe the TCCON and NDACC while the FTS measurements have higher precision and ac- ground-based FTS data sets that we use as the baseline for Atmos.
Load more

Recommended publications
  • World Meteorological Organization Global Atmosphere Watch
    WORLD METEOROLOGICAL ORGANIZATION GLOBAL ATMOSPHERE WATCH No. 140 WMO/CEOS REPORT on a STRATEGY for INTEGRATING SATELLITE and GROUND-BASED OBSERVATIONS of OZONE JANUARY 2001 WORLD METEOROLOGICAL ORGANIZATION GLOBAL ATMOSPHERE WATCH No. 140 WMO/CEOS REPORT on a STRATEGY for INTEGRATING SATELLITE and GROUND-BASED OBSERVATIONS of OZONE WMO TD No. 1046 List of Contents Foreword ...................................................................................................................................... iii Executive Summary...................................................................................................................... v Milestones in the History of Ozone ............................................................................................ ix 1. Introduction.......................................................................................................................... 1 1.1 The IGOS Strategy ................................................................................................. 1 1.2 The Ozone Project.................................................................................................. 2 1.3 Requirements and Data Sources .......................................................................... 5 1.4 The Objectives of the Report ................................................................................ 9 2. User Requirements............................................................................................................ 11 2.1 Sources of Information and Definitions
    [Show full text]
  • Neural Networks Algorithms for the Estimation of Atmospheric Ozone from Envisat-SCIAMACHY and Aura-OMI Measurements
    TOR VERGATA UNIVERSITY, ROME, ITALY Department of Computer, Systems and Industrial Engineering GeoInformation PhD Programme XXI Cycle Neural Networks algorithms for the estimation of atmospheric ozone from Envisat-SCIAMACHY and Aura-OMI measurements A thesis submitted in partial fulfillment for the degree of Doctor of Philosophy Mentor: Fabio Del Frate Candidate: Pasquale Sellitto February 2009 Dedicated to Chiara i \Nature - the Gentlest Mother is Impatient of no Child - The feeblest - or the waywardest - Her Admonition mild - In Forest - and the Hill - By Traveller - be heard - Restraining Rampant Squirrel - Or too impetuous Bird - How fair Her Conversation - A Summer Afternoon - Her Household - Her Assembly - And when the Sun go down - Her Voice among the Aisles Incite the timid prayer Of the minutest Cricket - The most unworthy Flower - When all the Children sleep - She turns as long away As will suffice to light Her lamps - Then bending from the Sky - With infinite Affection - And infiniter Care - Her Golden finger on Her lip - Wills Silence - Everywhere -" Emily Dickinson Acknowledgements Nel settembre 2005, da neolaureato in Fisica all'Universit`a\La Sapienza", decisi di partecipare all'esame di ammisione al corso di Dottorato di Ricerca in GeoInformazione, all'Universit`a\Tor Vergata", Dipartimento di Ingegneria dell'Informazione. Oggi posso ammetterlo, avevo letto, in fretta e furia solo 2 o 3 articoli sul telerilevamento dell'atmosfera da satellite, li avevo letti rapidamente e non ci avevo capito molto. Ero vestito da “fisico", il che scaten´oqualche ilarit`a 1, e non conoscevo nessuno a Tor Vergata. Avevo alle spalle un contratto (che avevo rifiutato) da studente di dottorato al Forschungszentrum J¨ulich e la ragionevole prospettiva di vincere una posizione analoga per il dottorato in Teler- ilevamento a \La Sapienza".
    [Show full text]
  • SCIAMACHY V8 Solar Spectral Irradiance Validation
    SCIAMACHY V8 Solar Irradiance Validation scilov15_report_solar_V2.tex Version 2.0, 27-11-2017 Page 1 of 17 SCIAMACHY V8 Solar Spectral Irradiance Validation Tina Hilbig, Mark Weber, Klaus Bramstedt and John P. Burrows Institut für Umweltphysik, Universität Bremen, Bremen, Germany Document Number : scilov15_report_solar_V2.tex Version : 2.0 Date : November 27, 2017 Contact : Mark Weber ([email protected]) Universität Bremen FB1 P.O. Box 330 440 D-28334 Bremen Status : final ESA SCILOV-15 Project Technical Note SCIAMACHY V8 Solar Irradiance Validation scilov15_report_solar_V2.tex Version 2.0, 27-11-2017 Page 2 of 17 Contents 1 Introduction . 3 2 Solar Spectral Irradiance . 3 2.1 Instrument . 3 2.2 Solar Measurements . 4 3 Comparison of different Data Product Versions . 5 3.1 Version History . 5 3.2 Solar Mean Reference Spectrum . 6 3.3 Time Series . 8 4 Comparison with other Solar Reference Spectra . 11 5 Conclusions & Outlook . 13 6 References . 15 ESA SCILOV-15 Project Technical Note SCIAMACHY V8 Solar Irradiance Validation scilov15_report_solar_V2.tex Version 2.0, 27-11-2017 Page 3 of 17 1 Introduction SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) aboard the ESA Envisat satellite platform provided atmospheric trace gas measurements on a global scale for nearly a decade from August 2002 to April 2012 (Burrows et al., 1995; Bovensmann et al., 2011, and references therein). The trace gas retrievals are based upon Sun-normalized radiances, which are limb or nadir radiances divided by the solar irradiance. SCIAMACHY observes, therefore, the Sun directly once a day. Like other UV satellite sounders, the SCIAMACHY spectrometer suffers from optical degradation due to polymerisation of optical surfaces from the harsh UV radiation in space (e.g.
    [Show full text]
  • Evaluating a New Homogeneous Total Ozone Climate Data Record from GOME/ERS-2, SCIAMACHY/Envisat and GOME-2/Metop-A M
    Evaluating a new homogeneous total ozone climate data record from GOME/ERS-2, SCIAMACHY/Envisat and GOME-2/MetOp-A M. E. Koukouli, Christophe Lerot, José Granville, Florence Goutail, Jean-Christopher Lambert, Jean-Pierre Pommereau, D. Balis, I. Zyrichidou, Michel van Roozendael, M. Coldewey-Egbers, et al. To cite this version: M. E. Koukouli, Christophe Lerot, José Granville, Florence Goutail, Jean-Christopher Lambert, et al.. Evaluating a new homogeneous total ozone climate data record from GOME/ERS-2, SCIA- MACHY/Envisat and GOME-2/MetOp-A. Journal of Geophysical Research: Atmospheres, American Geophysical Union, 2015, 120 (23), pp.12296-12312. 10.1002/2015JD023699. insu-01240107 HAL Id: insu-01240107 https://hal-insu.archives-ouvertes.fr/insu-01240107 Submitted on 31 Aug 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. PUBLICATIONS Journal of Geophysical Research: Atmospheres RESEARCH ARTICLE Evaluating a new homogeneous total ozone climate data 10.1002/2015JD023699 record from GOME/ERS-2, SCIAMACHY/Envisat, Key Points: and GOME-2/MetOp-A • Validation of Ozone-CCI total ozone products from GOME/ERS-2, M. E. Koukouli1, C. Lerot2, J. Granville2, F. Goutail3, J.-C.
    [Show full text]
  • Intercomparison of Ground- and Satellite-Based Total Ozone Data Products at Marambio Base, Antarctic Peninsula Region
    atmosphere Article Intercomparison of Ground- and Satellite-Based Total Ozone Data Products at Marambio Base, Antarctic Peninsula Region Klára Cˇ ížková 1,2,*, Kamil Láska 1 , Ladislav Metelka 2 and Martin Stanˇek 2 1 Department of Geography, Faculty of Science, Masaryk University, 611 37 Brno, Czech Republic; [email protected] 2 Solar and Ozone Observatory, Czech Hydrometeorological Institute, 500 08 Hradec Králové, Czech Republic; [email protected] (L.M.); [email protected] (M.S.) * Correspondence: [email protected] Received: 26 October 2019; Accepted: 15 November 2019; Published: 18 November 2019 Abstract: This study aims to compare the ground-based Brewer spectrophotometer total ozone column measurements with the Dobson spectrophotometer and various satellite overpass data available at Marambio Base during the period 2011–2013. This station provides a unique opportunity to study ozone variability near the edge of the southern polar vortex; therefore, many institutions, such as the National Meteorological Service of Argentina, the Finnish Meteorological Institute and the Czech Hydrometeorological Institute, have been carrying out various scientific activities there. The intercomparison was performed using total ozone column data sets retrieved from the ground-based instruments and from Ozone Monitoring Instrument (OMI)—Total Ozone Mapping Spectrometer (TOMS), OMI–Differential Optical Absorption Spectroscopy (DOAS), Global Ozone Monitoring Experiment 2 (GOME2), and Scanning Imaging Absorption Spectrophotometer for Atmospheric Cartography (SCIAMACHY) satellite observations. To assess the quality of the selected data products, comparisons with reference to the Brewer spectrophotometer single observations were made. The performance of the satellite observational techniques was assessed against the solar zenith angle and effective temperature, as well as against the actual shape of the vertical ozone profiles, which represent an important input parameter for the satellite ozone retrievals.
    [Show full text]
  • SCIAMACHY: Mission Objectives and Measurement Modes
    VOL. 56, NO.2 JOURNAL OF THE ATMOSPHERIC SCIENCES 15 JANUARY 1999 SCIAMACHY: Mission Objectives and Measurement Modes H. BOVENSMANN,J.P.BURROWS,M.BUCHWITZ,J.FRERICK,S.NOEÈ L, AND V. V. R OZANOV Institute of Environmental Physics, University of Bremen, Bremen, Germany K. V. CHANCE Harvard±Smithsonian Center for Astrophysics, Cambridge, Massachusetts A. P. H. GOEDE SRON Ruimetonderzoek, Utrecht, the Netherlands (Manuscript received 5 September 1997, in ®nal form 16 June 1998) ABSTRACT SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) is a spectrometer designed to measure sunlight transmitted, re¯ected, and scattered by the earth's atmosphere or surface in the ultraviolet, visible, and near-infrared wavelength region (240±2380 nm) at moderate spectral resolution (0.2± 1.5 nm, l/Dl ø 1000±10 000). SCIAMACHY will measure the earthshine radiance in limb and nadir viewing geometries and solar or lunar light transmitted through the atmosphere observed in occultation. The extraterrestrial solar irradiance and lunar radiance will be determined from observations of the sun and the moon above the atmosphere. The absorption, re¯ection, and scattering behavior of the atmosphere and the earth's surface is determined from comparison of earthshine radiance and solar irradiance. Inversion of the ratio of earthshine radiance and solar irradiance yields information about the amounts and distribution of important atmospheric constituents and the spectral re¯ectance (or albedo) of the earth's surface. SCIAMACHY was conceived to improve our knowledge and understanding of a variety of issues of importance for the chemistry and physics of the earth's atmosphere (troposphere, stratosphere, and mesosphere) and potential changes resulting from either increasing anthropogenic activity or the variability of natural phenomena.
    [Show full text]
  • SCIAMACHY - Exploring the Changing Earth’S Atmosphere
    springer.com Manfred Gottwald, Heinrich Bovensmann (Eds.) SCIAMACHY - Exploring the Changing Earth’s Atmosphere provides a complete description of an Earth Observation mission from requirements to results provides a comprehensive summary of the results of a state-of-the-art atmospheric remote sensing enterprise links instrument design and data retrieval for atmospheric absorption spectroscopy links actual measurements to current discussions about global change SCIAMACHY, the SCanning Imaging Absorption spectroMeter for Atmospheric CHar•tographY, is a passive sensor for exploring the Earth’s atmosphere. It is part of the payload of the European Earth Observation mission ENVISAT, launched on 1 March 2002. SCIAMACHY 2011, XVI, 225 p. observes absorption spectra of molecules from the UV (214 nm) to the short-wave infrared wavelength range (2386 nm) and derives the atmospheric composition – trace gases, aerosols, Printed book clouds – from these measurements. Having meanwhile successfully monitored and explored the Earth’s atmosphere for more than 8 years, new and exciting insights into the Earth- Hardcover atmosphere system are obtained. The provided global data sets do not only cover greenhouse 149,52 € | £119.99 | $179.99 gases and pollutants in the troposphere or the ozone chemistry in the stratosphere but even [1]159,99 € (D) | 164,47 € (A) | CHF reach up to the mesosphere and lower thermosphere. They contribute significantly to 176,50 atmospheric physics and chemistry as well as climate change research. SCIAMACHY is one of Softcover the major current Earth Observation undertakings of Germany, The Netherlands and Belgium, 130,83 € | £99.99 | $149.99 accomplished in cooperation with the European Space Agency (ESA).
    [Show full text]
  • Composition and Chemistry of the Neutral Atmosphere of Venus Emmanuel Marcq, Franklin P
    Composition and Chemistry of the Neutral Atmosphere of Venus Emmanuel Marcq, Franklin P. Mills, Christopher D. Parkinson, Ann Carine Vandaele To cite this version: Emmanuel Marcq, Franklin P. Mills, Christopher D. Parkinson, Ann Carine Vandaele. Composition and Chemistry of the Neutral Atmosphere of Venus. Space Science Reviews, Springer Verlag, 2018, 214, pp.article 10. 10.1007/s11214-017-0438-5. insu-01656562 HAL Id: insu-01656562 https://hal-insu.archives-ouvertes.fr/insu-01656562 Submitted on 6 Dec 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Composition and Chemistry of the Neutral Atmosphere of Venus Emmanuel Marcq1 · Franklin P. Mills2 · Christopher D. Parkinson3 · Ann Carine Vandaele4 E. Marcq [email protected] 1 LATMOS/Université de Versailles Saint-Quentin, Guyancourt, France 2 Australian National University, Canberra, Australia 3 University of Michigan, Ann Arbor, USA 4 Belgian Institute for Space Aeronomy, Uccle, Belgium Abstract This paper deals with the composition and chemical processes occurring in the neutral atmosphere of Venus. Since the last synthesis, observers as well as modellers have emphasised the spatial and temporal variability of minor species, going beyond a static and uniform picture that may have prevailed in the past.
    [Show full text]
  • Atmospheric Absorption Atmospheric Absorption
    Atmospheric Absorption Atmospheric Absorption The energy structure of atoms and molecules is composed of discrete energy levels. Energy levels are said to be quantised. Photons of electromagnetic radiation also have discrete energy, which is proportional to frequency via Plancks constant, h. Thus E = hf where f is the frequency. A photon with a frequency such that E1 - E0 = hf0 (where E1 and E0 correspond to a possible transition within the molecule) will be absorbed (as illustrated below) subject to probability whereas no other frequency will interact with the molecule; at least for this energy transition. As a result some energy will be removed from the photon field at exactly the frequency f0 and thus a spectral line will be observed at this frequency. Transitions can be electronic, vibrational or rotational. The energy levels involved for the different types of transition are generally well separated so that Eel > Evib > Erot. Rotational features in the spectrum typically occur in the far infrared. Vibrational features occur in the mid and near infrared whereas electronic transitions are mainly located in the UV and visible regions. For a given molecule, the contribution of the different possible transitions combined with different broadening effects results in complex absorption features as a function of wavelength. As an example, the graph below shows the absorption cross section of Ozone in the Higgins Bands (UV) for two different temperatures. http://envisat.estec.esa.nl/support-docs/atmospheric-absorption/atmospheric-absorption.html (1 of 3) [5/24/1999 11:50:14 AM] Atmospheric Absorption The actual shape of the aborption features and the wavelength regions where aborptions occur are different for each molecule.
    [Show full text]
  • Atmospheric Greenhouse Gases Retrieved from SCIAMACHY: Comparison to Ground-Based FTS Measurements and Model Results
    Atmos. Chem. Phys., 12, 1527–1540, 2012 www.atmos-chem-phys.net/12/1527/2012/ Atmospheric doi:10.5194/acp-12-1527-2012 Chemistry © Author(s) 2012. CC Attribution 3.0 License. and Physics Atmospheric greenhouse gases retrieved from SCIAMACHY: comparison to ground-based FTS measurements and model results O. Schneising1, P. Bergamaschi2, H. Bovensmann1, M. Buchwitz1, J. P. Burrows1, N. M. Deutscher1,3, D. W. T. Griffith3, J. Heymann1, R. Macatangay3, J. Messerschmidt4, J. Notholt1, M. Rettinger5, M. Reuter1, R. Sussmann5, V. A. Velazco1, T. Warneke1, P. O. Wennberg4, and D. Wunch4 1Institute of Environmental Physics (IUP), University of Bremen FB1, Bremen, Germany 2Institute for Environment and Sustainability (IES), European Commission Joint Research Centre (EC-JRC), Ispra, Italy 3School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia 4California Institute of Technology, Pasadena, California, USA 5Institute for Meteorology and Climate Research (IMK-IFU), Garmisch-Partenkirchen, Germany Correspondence to: O. Schneising ([email protected]) Received: 18 September 2011 – Published in Atmos. Chem. Phys. Discuss.: 26 October 2011 Revised: 27 January 2012 – Accepted: 30 January 2012 – Published: 9 February 2012 Abstract. SCIAMACHY onboard ENVISAT (launched in cribed to occurrences of undetected thin clouds. Based on 2002) enables the retrieval of global long-term column- the comparison with the reference data, we conclude that the averaged dry air mole fractions of the two most important carbon dioxide data set can be characterised by a regional rel- anthropogenic greenhouse gases carbon dioxide and methane ative precision (mean standard deviation of the differences) (denoted XCO2 and XCH4). In order to assess the quality of about 2.2 ppm and a relative accuracy (standard deviation of the greenhouse gas data obtained with the recently intro- of the mean differences) of 1.1–1.2 ppm for monthly average duced v2 of the scientific retrieval algorithm WFM-DOAS, composites within a radius of 500 km.
    [Show full text]
  • Analysis of MESSENGER/MASCS Data During Second Venus Flyby
    EPSC Abstracts Vol. 8, EPSC2013-156, 2013 European Planetary Science Congress 2013 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2013 Analysis of MESSENGER/MASCS data during second Venus flyby S. Pérez-Hoyos (1), A. García-Muñoz (2), A. Sánchez-Lavega (1), G. Holsclaw (3) and W.M. McClintock (3) (1) Dpto. Física Aplicada I, ETS Ingeniería UPV/EHU, Bilbao, Spain, (2) ESA/RSSD, ESTEC, The Netherlands, (3) Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA, ([email protected] / Fax: +34- 94-6014178) Abstract band in UVVIS detector and both the VIS and NIR bands in the VIRS spectrograph. In June 2007, the MESSENGER spacecraft performed its second Venus flyby during its travel to 2. Data analysis Mercury. The spacecraft acquired several spectra of the reflected sunlight from the equatorial region of Radiance measurements obtained were tranformed the planet and covering from the middle ultraviolet into absolute reflectivity (I/F). Since our radiative (195nm) to the near infrared (1450 nm) using the transfer codes are restricted to work under the plane- MASCS instrument (MUV-UVVS and VIRS parallel approximation, we restricted the 960 channels). In this work we present an analysis of the available spectra (VIRS channels) to 318 usable data and their spectral and spatial variability spectra with moderate values for the following the mission footprint on the Venus disk. In illumination/observation angles. Those spectra were order to reproduce the observed reflectivity and acquired at latitudes located in the band from the obtain information on the upper clouds and the Equator to 10º S while the spacecraft footprint moved unknown UV absorber, we use XtraRT, a radiative from the limb of the planet close to the sub-solar transfer code based on DISORT and the HITRAN point to the terminator and close to the sub-observer database, which includes SO, SO2, CO2 and H2O absorption together with absorption and scattering by mode-1 and mode-2 cloud particles.
    [Show full text]
  • Monitoring Aerosol Presence Over a 15-Year Period Using the Absorbing Aerosol Index Measured by Gome-1, Sciamachy, and Gome-2
    MONITORING AEROSOL PRESENCE OVER A 15-YEAR PERIOD USING THE ABSORBING AEROSOL INDEX MEASURED BY GOME-1, SCIAMACHY, AND GOME-2 L. G. Tilstra1, M. de Graaf1,2, O. N. E. Tuinder1, R. J. van der A1, and P. Stammes1 1Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, 3730 AE De Bilt, The Netherlands 2Delft University of Technology, P.O. Box 5, 2600 AA Delft, The Netherlands Email: [email protected], [email protected], [email protected], [email protected], [email protected] ABSTRACT In this equation, Robs refers to reflectances measured by one of the three satellite instruments, while RRay refers to modelled Rayleigh reflectances. The symbol λ refers to In this paper we study 15-year long time series of the the first, shortest wavelength of the AAI wavelength pair, Absorbing Aerosol Index (AAI) for a selection of the which is 340 nm. The surface albedo As used in the sim- most prominent aerosol producing regions on the globe. ulations for this wavelength is assumed to be the same as The time series of the AAI were recorded by the satel- the surface albedo at the second wavelength λ0 = 380 nm. lite instruments GOME-1, SCIAMACHY, and GOME-2 The surface albedo at 380 nm in turn is found from re- aboard the ERS-2, Envisat, and MetOp-A satellites, re- quiring that the simulated Rayleigh reflectance equals the spectively. These three satellite instruments suffer, each measured reflectance at this wavelength. That is, we have in their own way, from severe instrument degradation in the following two constraints: the ultraviolet (UV) wavelength range from which the AAI is derived.
    [Show full text]