Abstracts

1. Gijs van Soest, L. G. Tilstra, P. Stammes (KNMI)
   Large scale validation of SCIAMACHY reflectances in the UV
   In this paper we present an extensive validation of calibrated SCIAMACHY nadir reflectances in the UV (240-350 nm) by comparison with spectra calculated with a fast radiative transfer model. A total of 9 months of data has been analyzed. This is the first reflectance validation study incorporating a large amount of data. It is shown that this method is a valuable tool for spotting spatial and temporal anomalies. We conclude that SCIAMACHY reflectance data in this wavelength range are stable over the investigated period. In addition, we show an example of an anomaly in the data due to an error in the processing chain that could be detected by our comparison. This validation method could be very useful too for validation of other satellite spectrometers, such as OMI and GOME-2.
   
   
2. Thomas Wagner (IUP-Heidelberg) and Andreas Richter (IFE)
   First applications of SCIAMACHY nadir UV/vis measurements
   SCIAMACHY nadir measurements in the UV/visible spectral range are very similar to GOME measurements. Therefore, the SCIAMACHY data set can be used to continue the existing GOME dataset which is of particular interest for the observation of long term changes of atmospheric composition. In addition, SCIAMACHY measurements provide much better spatial resolution which is a substantial improvement for tropospheric measurements, in particular for species with short life time such as NO2.
   In the presentation, some highlights of recent scientific applications of SCIAMACHY nadir UV/vis measurements are presented including the detection of NOx emissions from ships, long term changes of NO2 in Asia, monitoring of chlorine activation in polar air masses and the study of the link between frost flowers and bromine release in the polar springtime troposphere.
   
   
3. Michael Buchwitz, R. de Beek, J.P. Burrows (IUP/IFE-Bremen),
   C. Frankenberg, T. Wagner, U. Platt (IUP-Heidelberg),
   A. Gloudemans, H. Schrijver, Q. Kleipool, G. Lichtenberg, R. van Hees, M. van den Broek, A. G. Straume, I. Aben (SRON)
   SCIA near-infrared/nadir observations: Greenhouse gas measurements and applications
   The SCIAMACHY near-infrared nadir spectra contain information about the total columns of various important Greenhouse gases (CO2, CH4, N2O, H2O) including carbon monoxide (CO). The main scientific objective of the measurements of the relatively well-mixed Greenhouse gases CH4 and CO2 is to better constrain their surface fluxes (sources and sinks) than currently possible with the highly precise but rather sparse network of ground stations. A better understanding of their sources and sinks is important, e.g., to predict their future concentrations in a changing climate. This however is a challenging task as it requires very high precision and accuracy of the satellite measurements. Here we give an overview about what has been achieved until now using different approaches developed at three different institutions for the retrieval of CO2, CH4, CO, and H2O columns from the SCIAMACHY spectra.
   
   
4. Christian von Savigny, A. Rozanov, G. Rohen, K.-U. Eichmann, J. W. Kaiser, M. Sinnhuber, M. Scharringhausen, H. Bovensmann, and J. P. Burrows (IFE)
   Stratospheric and Mesospheric Applications of SCIAMACHY limb scattering observations
   A wealth of atmospheric absorption and emission features of different molecular and atomic constituents (neutral and ionic) appear within the spectral range covered by SCIAMACHY. Although the main focus of the SCIAMACHY mission is the stratosphere, the instrument already proved to be able to make important contributions to a better understanding of physical and chemical processes in the mesosphere and lower thermosphere. This presentation will provide an overview of the existing scientific data products retrieved from SCIAMACHY limb observations, both on the day and the night side of the Earth. Daytime applications include the retrieval of stratospheric profiles of O3, NO2, BrO, and OClO, mesospheric O3 profiles, the detection and mapping of polar stratospheric clouds (PSCs), as well as noctilucent clouds/polar mesospheric clouds (NLCs/PMCs). For NLCs the derivation of particle sizes has been demonstrated. The eclipse observations provide for the first time near-global measurements of the OH* (3-1) rotational temperature near the mesopause. Furthermore, several metallic emissions have been identified in the limb spectra that can be used to retrieve vertical profiles of these constituents. Several interesting atmospheric phenomena - e.g., the unprecedented major stratospheric warming in September 2002 or the impact of the October/November 2003 solar proton events on the composition of the Earth atmosphere - were already studied with SCIAMACHY limb scattering observations.
   
   
5. K.H. Fricke and U. Blum (U. Bonn)
   U. Bonn Lidar at Esrange used for SCIAMACHY validation
   Data from the U. Bonn lidar at the Esrange in northern Sweden were to be used for validation of temperatures and cloud top pressures in the ESA operational products derived from Sciamachy measurements. Unfortunately such Sciamachy data products are not yet available by the date of this workshop. For this intended validation we had collected lidar profiles with a total integration time exceeding 1000 hours. Our lidar data were used for the validation of Mipas and Gomos temperature profiles in the middle atmosphere.
   
   
6. Wolfgang von Hoyningen-Hüne (IFE)
   Determination of Aerosol Optical Thickness from SCIAMACHY L1 Data
   Aerosol products from SCIAMACHY suffered from the insufficient radiometric calibration in the regular L1 processing, (processor version V 4.02b). Thus the formal determination of aerosol optical thickness gave physically useless results and showed the significant underestimation of the top-of-atmosphere reflectance in bands 3, 4 and 5. Comparisons with simultaneous observations of the top-of-atmosphere reflectance from MERIS observations enables a quantifications of this underestimation (-10 ... 20 %) and the derivation of correction factors for selected channels of the SCIAMACHY L1 data. An application of these correction factors moved the reflectance in a useful range and it could be shown, that aerosol optical thickness in a possible range could be obtained from SCIAMACHY observations. The obtained correction factors are in agreement with the recalculations of the radiometric key data derived from the spectralon measurements.
   The aerosol optical thickness is retrieved by the BAER (Bremen AErosol Retrieval) approach, c.f. von Hoyningen-Hüne et al., 2003, specified for selected SCIAMACHY channels between 0.423 and 0.870 µm. A specific version of BAER - SCIA-BAER has been developed, adapted to the specific conditions of SCIAMACHY data, including the derived correction factors. The obtained first results of the aerosol optical thickness have been compared with retrievals made with MERIS L1 data from the same scenes. Also ground-based measurements from AERONET instruments within the scene are used for comparison. For simple ground conditions, sea surface outside of sun-glint and flat land surfaces with intensive green vegetation cover the aerosol optical thickness was in the range of the few AERONET results and the retrievals with BAER, using MERIS L1 data. Results of the first application of the SCIA-BAER program are presented by von Hoyningen-Huene et al. 2004.
   Unless this progress, remaining problems will be visible in the test results. A bias of the top-of atmosphere reflectance from west to east, probably caused by an insufficient polarization correction is now visible, giving higher aerosol optical thickness at the west side of the swath than at the east side. For this empirical correction factors will be needed for a derivation of aerosol optical thickness.
   References:
   von Hoyningen-Hüne, W., M. Freitag, and J. B. Burrows, Retrieval of aerosol optical thickness over land surfaces from top-of-atmosphere radiance, J. Geophys. Res., 108(2003), D9 4260, doi:10.1029/2001JD002018, 2003.
   von Hoyningen-Hüne, W., Kokhanovsky, A.A., Wuttke, M.W., Buchwitz, M., Noel, S., Gerilowski, K., Burrows, J.P., Latter, B., Siddans, R., Kerridge, B.J.: Validation of SCIAMACHY Top-of-Atmosphere Reflectance for Aerosol Remote Sensing Using MERIS L1 Data. ACP (special issue SCIAMACHY Validation), accepted 2004
   Wolfgang von Hoyningen-Hüne VALIDATION OF AEROSOL PRODUCTS DERIVED FROM SCIAMACHY Proceedings of the Second Workshop on the Atmospheric Chemistry Validation of ENVISAT (ACVE-2), ESA-ESRIN, Frascati, Italy, 3-7 May 2004 (ESA SP-562, August 2004) ESC01WVH
   
   
7. Gerhard Kopp (1), E. Brinksma (2), H. Eskes (2), G. Hochschild (1), P. Hoffmann (3), U. Raffalski (4), and R. Van der A (2)
   (1) Institute of Meteorology and Climate Research, Forschungszentrum Karlsruhe and Universität Karlsruhe, Germany
   (2) Koninklijk Nederlands Meteorologisch Instituut, De Bilt, Netherlands
   (3) Universidad de Los Andes, Mérida, Venezuela
   (4) Swedish Institute of Space Physics, Kiruna, Sweden
   Validation of SCIAMACHI total ozone column measurements by ground-based microwave observations at Kiruna, Mount Zugspitze, and Mérida
   Ground-based millimeter wave measurements in the Arctic, the midlatitudes, and in the Tropics are used for the validation of SCIAMACHY total ozone column measurements. The millimeter wave measurements at Kiruna used for this study are routinely carried out at the Swedish Institute of Space Physics (IRF) at Kiruna, Sweden, since 2002. The Institute of Meteorology and Climate Research (IMK) of the Forschungszentrum Karlsruhe performed millimeter wave measurements on the Zugspitze in the Alps in 2003 and at Mérida in the Venezuelan Andes since March 2004. These measurements are carried out in cooperation with the Universidad des Los Andes (ULA) at Mérida.
   For the years 2003 and 2004 SCIAMACHY ozone columns retrieved using the TOSOMI algorithm of the Koninklijk Nederlands Meteorologisch Instituut (KNMI) were used for validation. The columns of the millimeter wave measurements cannot be compared directly with the SCIAMACHY total columns since the millimeter wave radiometer is not sensitive in the troposphere. Therefore only stratospheric columns of the radiometer were compared with SCIAMACHY total columns resulting in an offset between both measurements due to the missing lower part of the ozone column in the microwave measurements. But besides this offset both time series of ozone over Kiruna evolve quite parallel in 2003 resulting in a mean difference of 76.8 ± 31.9 DU. In the Zugspitze measurements the mean difference amounts to 50.1 ± 34.1 DU. The mean difference is lower than that of the Kiruna measurements probably because of the higher altitude of the measurement site on the Zugspitze, the standard deviation is in the same order for both time series (about 10%).
   The SCIA/5.04 L2-data for Kiruna in 2003 and 2004 show larger systematic differences to the ground-based data for measurements taken during low solar zenith angles shortly before the polar night 2003, but if one omits these data the mean differences are similar to that of the KNMI data, the offset is slightly larger but the scatter is a little bit smaller. The mean difference for the Zugspitze data of the SCIA/5.04 L2-data is also comparable to that of the KNMI data, also with a slightly larger offset and a somewhat smaller scatter. The comparison of the data measured at Mérida yields a low offset between SCIAMACHY and microwave data of only -16.4 DU probably due to the high altitude of this site. The scatter between both time series amounts to 11 DU and is the lowest of all comparisons presented here.
   
   
8. Ralf Sussmann (IMK-IFU)
   SCIAMACHY Validation with Solar FTIR Spectrometry at the NDSC Primary Station Zugspitze
   Column densities/vertical profiles of O3, NO2, CO, CH4, and N2O (and others) are being retrieved continuously the year round whenever clear sky conditions allow from solar FTIR spectrometry at the Permanent Ground-Truthing Facility Zugspitze/Garmisch. This paper gives an overview on the correlative studies performed for all processor versions of SCIAMACHY operational O3 and NO2 columns, as well as for all processor versions and releases of the scientific (UNI Bremen) column products for NO2, CO, CH4, and N2O. The results point to a striking difference in the NO2 operational versus scientific retrievals in monitoring the annual cycle [1]. Furthermore, we have shown an approach [2,3] to assess the capability of the WFMDOAS infrared retrievals (CO, CH4, N2O) to reflect the natural atmospheric inter-annual variability (annual cycle and day-to-day scatter). This is achieved by applying regressions to the ground-based and space borne time series, and comparing their statistical parameters as a function of the selection criteria applied to the satellite data set (pixel selection radius around Zugspitze, retrieval error boundary, cloud mask) [2,3].
   References:
   [1] Sussmann, R., W. Stremme, M. Rettinger, and A. Rockmann, Validation of SCIAMACHY Operational Near-Real-Time Level-2 Products by FTIR at the Ground Truthing Station Zugspitze, in "Proc. ACVE-2 workshop", 3-7 May 2004, ESA-ESRIN, Frascati, Italy, SP-562, 2004.
   [2] Sussmann, R., M. Buchwitz, and A. Richter, Validation of SCIAMACHY Scientific Retrievals of CO, CH4, N2O, and NO2 by FTIR at the Ground Truthing Station Zugspitze, in "Proc. ACVE-2 workshop", 3-7 May 2004, ESA-ESRIN, Frascati, Italy, SP-562, 2004.
   [3] Sussmann, R., and M. Buchwitz, Validation of ENVISAT/SCIAMACHY columnar CO by FTIR profile retrievals at the Ground Truthing Station Zugspitze, Atmos. Chem. Phys., submitted 2004.
   
   
9. Thorsten Warneke (1), J. Notholt (1), A. Schulz (2), V. Velazco (1), O.Schrems (2)
   (1) Institute of environmental physics, University of Bremen, Bremen
   (2) Alfred Wegener Institute, Bremerhaven/Potsdam
   Ground-based FTIR measurements in Bremen, Ny-Alesund and on board Polarstern
   Ground-based, high-resolution FT-solar absorption spectra have been obtained in Bremen, Spitsbergen and during three cruises with the research vessel Polarstern on the Atlantic between 55°N and 35°S. The purpose of these measurements was the validation of the SCIAMACHY satellite instrument on ENVISAT. The measurements were successful and column densities of more than 20 different atmospheric trace gases could be retrieved from these spectra. Among these gases are O3, NO2, N2O, CO, CH4, CO2, CH2O, NO and H2O which are SCIAMACHY target gases. Selected results and comparisons with scientific and operational SCIAMACHY Level-2 products are presented.
   
   
10. Thomas Medeke, S. Fietkau, H. Oetjen, A. Richter, F. Wittrock, and J.P. Burrows
    Institute of Environmental Physics (IUP), University of Bremen
    SCIAMACHY validation with the BREDOM network
    BREDOM (Bremian DOAS Network for Atmospheric Measurements) is a network of high sensitivity ground-based DOAS instruments at arctic, middle and low latitudes. Target species of the measurements are O3 and NO2 as well as minor absorbers (e.g. BrO, HCHO). All measurement quantities from the DOAS instruments can be used for the validation of UV/visible satellite instruments such as GOME, SCIAMACHY or OMI, which do use a very similar measurement technique and cover the same species. At this workshop selected results and comparisons with scientific and operational SCIAMACHY Level-2 products will be presented.
    
    
11. Klaus-Peter Heue (IUP Heidelberg) and Ping Wang (IFE)
    SCIAMACHY validation with the Airborne Multi AXis Differential Optical Absorption Spectroscopy instrument (AMAXDOAS)
    The AMAXDOAS instrument on board the DLR-Falcon is an airborne multi-axis UV/visible spectrometer which was designed specifically for the validation of products from the SCIAMACHY instrument on ENVISAT. The AMAXDOAS instrument was flown during two large SCIAMACHY validation campaigns in September 2002 and February and March 2003. In these presentations we will briefly introduce the instrument and the campaign. The focus will be on the O3 and NO2 validation results with the SCIAMACHY level 2 data (version 5.01 in Sep. 2002 and version 5.04 in Feb. and Mar 2003) and Bremen scientific NO2 product. The AMAXDOAS BrO, OClO measurements and tropospheric NO2 retrieval at cloudy situation are also presented as examples for scientific utilization. For cloud free situations a validation of tropospheric, SCIAMACHY data will be presented, for the Bremen scientific NO2 columns. A validation for tropospheric NO2 in a cloudy situation is in progress, we will present the present status.
    
    
12. Henk Eskes, Ronald van der A, Ellen Brinksma, Pepijn Veefkind, Johan de Haan
    Royal Netherlands Meteorological Institute, KNMI
    Retrieval, validation and assimilation of SCIAMACHY ozone columns
    In this contribution we will discuss a new algorithm, called TOSOMI, to retrieve total ozone from SCIAMACHY observations. It is based on the DOAS algorithm developed for GOME (TOGOMI algorithm) and OMI. Innovations include a new procedure to compute the air-mass factor (empirical approach) and a new formulation to account for rotational Raman scattering. The SCIAMACHY columns for 2003/2004 are assimilated in the ozone chemistry-transport model TM3DAM. The observation minus forecast statistics was used to verify the retrieval results, and several problems have been identified with this procedure during the development of the TOSOMI algorithm. Validation results with ground-based measurements (Brewer, Dobson) and the TOMS version 8 ozone columns will be presented. The SCIAMACHY total ozone retrieval, data assimilation analyses and ozone forecasts are all available in near-real time on the TEMIS project web site www.temis.nl.
    
    
13. Astrid Bracher, K. Bramstedt, M. Weber, J. P. Burrows
    Institute of Environmental Physics (IUP), University of Bremen
    Validation of SCIAMACHY (v5.01/5.04) O3 and NO2 columns with GOME (v3.0 and IUP retrievals WFDOAS)
    The operational SCIAMACHY nadir data products of O3 and NO2 columns are validated by comparison with GOME 3.0 and for ozone additionally to GOME WFDOAS. Compared to former data versions, SCIAMACHY ozone columns versions 5.01/5.04 show a large improvement (an agreement within 2% with GOME 3.0 and GOME WFDOAS), but SCIAMACHY NO2 columns compared to GOME 3.0 still show large deviations and a latitudinal dependence. Details about this study will be presented at this workshop.
    
    
14. Stefan Noel, M. Buchwitz, H. Bovensmann, J. P. Burrows
    Institute of Environmental Physics/Remote Sensing, University of Bremen, Germany
    SCIAMACHY water vapour retrieval using AMC-DOAS
    Measurements of the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on ENVISAT have been used to derive global water vapour total column amounts over ocean and land. For this purpose, the Air Mass Corrected Differential Optical Absorption Spectroscopy (AMC-DOAS) approach, which has already been successfully used with GOME data, has been applied to SCIAMACHY's nadir measurements.
    Whereas operational SCIAMACHY water vapour products are derived from measurements in the NIR, the AMC-DOAS algorithm is applied to the spectral region around 700 nm where both water vapour and molecular oxygen absorptions are present.
    This presentation will show results of first long-term comparisons of the SCIAMACHY scientific total water vapour columns derived with the AMC-DOAS method with corresponding SSM/I and ECMWF water vapour measurements.
    
    
15. Jolanta Kusmierczyk-Michulec, G. de Leeuw
    TNO Physics and Electronics Laboratory
    Aerosol optical thickness retrieval over land and water using SCIAMACHY/GOME data
    An algorithm for the retrieval of the aerosol optical thickness over land and over water from SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric ChartographY) is presented. Because calibrated data are not yet available for the SCIAMACHY channels used by the algorithm, the concepts were tested with GOME (Global Ozone Monitoring Experiment) data. The cloud fraction in the GOME pixels has been determined using the FRESCO (Fast Retrieval Scheme for Clouds from the Oxygen A Band) algorithm. Surface contributions to the TOA reflectance are determined from the GOME surface reflectance database (Koelemijer et al., 2003). The aerosol retrieval algorithm uses Look Up Tables (LUT) that were created using the radiative transfer model 6S. The algorithm allows for the retrieval of aerosol types characterized by Ångstrom coefficients in the range from -0.1 to 2.8. Comparison of the results with AERONET sun photometer data for 12 sites in Europe and Africa shows very good agreement.
    
    
16. Alexander KokhanovskyV.V. Rozanov, W. von Hoyningen-Hüne, J.P. Burrows (IFE)
    Semianalytical cloud retrieval algorithm and its application to data from multiple optical instruments on spaceborne platforms: SCIAMACHY, MERIS, MODIS, SeaWiFS and GOME
    A recently developed cloud retrieval algorithm for the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) is briefly presented and validated using independent and well tested cloud retrieval techniques based on the look-up-table approach for MODeration resolutIon Spectrometer data. The results of the cloud top height retrievals using measurements in the oxygen A-band by an airborne crossed Czerny-Turner spectrograph and the Global Ozone Monitoring Experiment (GOME) instrument are compared with those obtained from airborne dual photography and retrievals using data from Along Track Scanning Radiometer (ATSR-2), respectively.
    In addition, the Semianalytical CloUd Retrieval Algorithm (SACURA) is applied to SCIAMACHY data. In particular, for the first time we derive simultaneously cloud optical thickness (COT), liquid water path (LWP), cloud top height (CTH), and cloud thermodynamic state(CTS) using SCIAMACHY measurements in the visible (442nm, COT), in the oxygen A-band(755-775nm, CTH) and in the infrared (1550nm/1670nm, CTS). SCIAMACHY-measured backscattered light radiance is compared with that obtained from the Medium Resolution Imaging Spectrometer (MERIS) data on board ENVISAT. MERIS has better spatial resolution and observe almost the same scene as SCIAMACHY does.
    
    
17. Yasjka Meijer (RIVM)
    Envisat Quality Assessment with Lidar (EQUAL), a project to support the long-term validation of SCIAMACHYs ozone and temperature profiles
    In 2004 ESA started several new projects to support the long-term validation of ENVISAT's atmospheric chemistry instruments. The Envisat Quality Assessment with Lidar (EQUAL) project involves eleven lidar stations around the world measuring ozone and temperature profiles. The participating stations are (from north to south) Eureka, Ny Alesund, Alomar, Esrange, Hohenpeissenberg, OHP, Tsukuba, Table Mountain, Mauna Loa, La Reunion, and Lauder. In 2003 in total over 800 files were submitted resulting from these lidar observtations, and in 2004 already over 600 files. The project is led by RIVM in Bilthoven where the coordination and some of the data conversion to HDF for the NILU database takes place. In addition, within this project dedicated validation activities are performed at RIVM to assess the quality of the ozone and temperature profiles of ENVISAT. The main focus wil be on the quality of the official ESA products, i.e., for SCIAMACHY the offline limb profiles, but as long as these products are unavaiable the focus will be shifted toward scientific products retrieved from both the limb and nadir observations of SCIAMACHY. In this presentation the aim, set-up and potential of the EQUAL project will be presented.
    
    
18. Dorien Lolkema (RIVM and KNMI)
    Validation of SCIAMACHY ozone profiles: an extensive approach
    So far, the validation of SCIAMACHY ozone profiles has been limited to a number of case studies. We will make a start with a more extensive approach. We will look at a large number of groundbased data from stations all over the world. In this way, we can make statements on the quality of the SCIAMACHY ozone profiles based on statistics. Also, we can use subsets of the groundbased data to make analyses on the sensitivity of the SCIAMACHY ozone measurements to specific parameters like geographical location, solar zenith angle, etc. In this presentation, this extensive approach for the validation of SCIAMACHY ozone profiles will be laid out.
    
    
19. Arjo Segers (KNMI)
    Validation of SCIAMACHY limb ozone profiles
    A data set of limb ozone profiles has been retrieved from SCIAMACHY by IFE Bremen. For the period up to december 2003, the data set suffers from the imprecize knowledge of the pointing of the instrument, leading to a shift in the ozone profile with respect to altitude. To identify a correction for the pointing error, and an an overall estimate of the quality, the limb profiles have been compared with two other ozone data sets. First, the scia ozone profiles have been compared to a database of ozone sondes that collects practically all ozone sondes launched during the period under investigation. Second, a comparison has been made with global ozone fields simulated with a CTM. In a later stage of the validation project, the error statistics obtained by this comparisons will be used in an assimilation procedure to obtain quality estimates for each individual profile.
    
    
20. Michael Buchwitz, R. de Beek, H. Bovensmann, J.P. Burrows
    Institute of Environmental Physics (iup) / Remote Sensing (ife), University of Bremen
    Carbon monoxide, methane, carbon dioxide, and nitrous oxide columns as retrieved from SCIAMACHY by WFM-DOAS: Algorithm, released data products, and initial validation/verification
    The scientific (non-operational) retrieval algorithm Weighting Function Modified (WFM) DOAS has been applied to SCIAMACHY near-infrared nadir spectra to obtain vertical columns of carbon monoxide (CO), methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) as well as O2-normalized columns of the well-mixed Greenhouse gases CH4, CO2, and N2O, the so called dry air column averaged mixing ratios XCH4, XCO2, and XN2O. The current version of this algorithm is v0.4. For the year 2003 WFM-DOAS v0.4 data products have been generated and made available to the SCIAMACHY validation community. Recently it has been found that the methane columns show a time dependent bias closely correlated with the time dependent throughput of SCIAMACHY channel 8 resulting from ice layer growths on the channel 8 detector. A first order bias correction has been applied to the methane columns and they have been normalized to CO2 to obtain an improved v0.41 XCH4 data product. The talk will give an overview about the WFM-DOAS algorithm, the released data products and our validation/verification activities using independent measurements (MOPITT/Terra) and global models (TM3/KNMI, TM5/JRC-Ispra, IMAGES/BIRA-IASB, and TM3/MPI-Jena).
    
    
21. M. De Mazière (1), Bart Dils (1), M. Buchwitz (2), R. De Beek (2), C. Frankenberg (3), A. Gloudemans (4), H. Schrijver (4), et al.
    (1) Belgian Institute for Space Aeronomy
    (2) Institute of Environmental Physics, University of Bremen
    (3) Institute of Environmental Physics, University of Heidelberg
    (4) Space Research Organisation of the Netherlands, SRON
    Contribution to the validation of SCIAMACHY scientific data products for CO, CH4, CO2, and N2O total column amounts using ground-based network FTIR data
    In order to assess the quality of SCIAMACHY scientific data products for CO, CH4, N2O and CO2, correlative Fourier transform infrared (FTIR) data from twelve stations of the worldwide Network for the Detection of Stratospheric Change (NDSC) have been collected since July 2002. The SCIAMACHY spectra in the near infrared have been processed by different teams in Europe with three different algorithms to derive total column amounts of CO, CH4, N2O and CO2, for the year 2003. The algorithms and teams are WFM-DOAS (University of Bremen), IMLM (SRON) and IMAP (Univ. of Heidelberg). The satellite data have been compared with the ground-based data as a function of time and latitude, while taking into account different selection criteria. In order to have a good qualitative indication of the capability of SCIAMACHY to detect short- and mid-term variability, as for example the seasonal variation, time series of SCIAMACHY data have been compared to time series of ground-based FTIR data. For obtaining a quantitative estimate of the possible bias and residual dispersion of the SCIAMACHY data, the data have been compared to polynomial fits through the ground-based FTIR time series that represent the mid-term variability in the ground-based data reasonably well. The results of the intercomparisons are discussed in terms of the comparison conditions and data selection criteria.