Publications (17)0 Total impact
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Article: Validation and data characteristics of methane and nitrous oxide profiles observed by MIPAS and processed with Version 4.61 algorithm
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ABSTRACT: The ENVISAT validation programme for the atmospheric instruments MIPAS, SCIAMACHY and GOMOS is based on a number of balloon-bone, aircraft and ground-based correlative measurements. In particular the activities of validation scientists were coordinated by ESA within the ENVISAT Stratospheric Aircraft and Balloon Campaign of ESABC. As part of a series of similar papers on other species [this issue] and in parallel to the contribution of the individual validation teams, the present paper provides a synthesis of comparisons performed between MIPAS CH<sub>4</sub> and N<sub>2</sub>O profiles produced by the current ESA operational software (Instrument Processing Facility version 4.61 or IPF v4.61) and correlative measurements obtained from balloon and aircraft experiments as well as from satellite sensors or from ground-based instruments. The MIPAS-E CH<sub>4</sub> values show a positive bias in the lower stratosphere of about 10%. In case of N<sub>2</sub>O no systematic deviation with respect to the validation experiments could be identified. The individual used MIPAS data version 4.61 still exhibits some unphysical oscillations in individual CH<sub>4</sub> and N<sub>2</sub>O profiles caused by the processing algorithm (with almost no regularization). Taking these problems into account, the MIPAS CH<sub>4</sub> and N<sub>2</sub>O profiles are behaving as expected from the internal error estimation of IPF v4.61.01/2007; -
Article: First results of ozone profiles between 35 and 65 km retrieved from SCIAMACHY limb spectra and observations of ozone depletion during the solar proton events in …
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ABSTRACT: Ozone density profiles between 35 and 65 km altitude are derived from scattered sunlight limb radiance spectra measured by the SCIAMACHY instrument on the Envisat satellite. The method is based on the inversion of normalized limb radiance pro-files in the Hartley absorption bands of ozone at selected wavelengths between 250 and 310 nm. It employs a non-linear New-tonian iteration version of Optimal Estimation (OE) coupled with the radiative transfer model SCIARAYS. The limb scatter technique combined with a classical OE retrieval in the short-wave UV-B and long-wave UV-C delivers reliable results as shown by a first comparison with MIPAS V4.61 profiles yielding agreement within 10% between 38 and 55 km. An overview of the methodology and an initial error analysis are presented. Furthermore the effect of the solar proton storm between 28 October and 6 November 2003 on the ozone concentration profiles is shown. They indicate large depletion of ozone of about 60% at 50 km in the Northern hemisphere, a weaker depletion in the Southern hemisphere and a dependence of the depletion on the Earth's magnetic field. -
Article: Validation of ENVISAT trace gas data products by comparison with GOME / ERS-2 and other satellite sensors
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Article: Validation of ozone measurements from the Atmospheric Chemistry Experiment (ACE)
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ABSTRACT: This paper presents extensive validation analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. The ACE satellite instruments operate in the mid-infrared and ultraviolet-visible-near-infrared spectral regions using the solar occultation technique. In order to continue the long-standing record of solar occultation measurements from space, a detailed quality assessment is required to evaluate the ACE data and validate their use for scientific purposes. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the mean differences range generally between 0 and +10% with a slight but systematic positive bias (typically +5%). At higher altitudes (45–60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments by up to ~40% (typically +20%). For the ACE-MAESTRO version 1.2 ozone data product, agreement within ±10% (generally better than ±5%) is found between 18 and 40 km for the sunrise and sunset measurements. At higher altitudes (45–55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (by as much as -10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS and indicate a large positive bias (+10 to +30%) in this altitude range. In contrast, there is no significant difference in bias found for the ACE-FTS sunrise and sunset measurements. These systematic effects in the ozone profiles retrieved from the measurements of ACE-FTS and ACE-MAESTRO are being investigated. This work shows that the ACE instruments provide reliable, high quality measurements from the tropopause to the upper stratosphere and can be used with confidence in this vertical domain. -
Article: Using a photochemical model for the validation of NO<sub>2</sub> satellite measurements at different solar zenith angles
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ABSTRACT: SCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography) aboard the recently launched Environmental Satellite (ENVISAT) of ESA is measuring solar radiance upwelling from the atmosphere and the extraterrestrial irradiance. Appropriate inversion of the ultraviolet and visible radiance measurements, observed from the atmospheric limb, yields profiles of nitrogen dioxide, NO<sub>2</sub>, in the stratosphere (SCIAMACHY-IUP NO<sub>2</sub> profiles V1). In order to assess their accuracy, the resulting NO<sub>2</sub> profiles have been compared with those retrieved from the space borne occultation instruments Halogen Occultation Experiment (HALOE, data version v19) and Stratospheric Aerosol and Gas Experiment II (SAGE II, data version 6.2). As the HALOE and SAGE II measurements are performed during local sunrise or sunset and because NO<sub>2</sub> has a significant diurnal variability, the NO<sub>2</sub> profiles derived from HALOE and SAGE II have been transformed to those predicted for the solar zenith angles of the SCIAMACHY measurement by using a 1-dimensional photochemical model. The model used to facilitate the comparison of the NO<sub>2</sub> profiles from the different satellite sensors is described and a sensitivity ananlysis provided. Comparisons between NO<sub>2</sub> profiles from SCIAMACHY and those from HALOE NO<sub>2</sub> but transformed to the SCIAMACHY solar zenith angle, for collocations from July to October 2002, show good agreement (within +/-12%) between the altitude range from 22 to 33km. The results from the comparison of all collocated NO<sub>2</sub> profiles from SCIAMACHY and those from SAGE II transformed to the SCIAMACHY solar zenith angle show a systematic negative bias of 10 to 35% between 20km to 38km with a small standard deviation between 5 to 14%. These results agree with those of Newchurch and Ayoub (2004), implying that above 20km NO<sub>2</sub> profiles from SAGE II sunset are probably somewhat high. -
Article: MIPAS ozone validation by satellite intercomparisons
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Article: Validation of ENVISAT trace gas data products by comparison with GOME/ERS-2 and other satellite sensors.
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Article: Comparison of total ozone from the satellite instruments
Atmospheric Chemistry and Physics. 3(2003):1409-1419. -
Article: Advanced MIPAS-Level-2 Data Analysis (AMIL2DA)
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ABSTRACT: Final report, June 2003, EC Project EVG1-CT-1999-00015. -
Article: Overview on validation of MIPAS H2O vapour by comparison with independent satellite measurements
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ABSTRACT: The water vapour operational data products from MIPAS (V4.61) have been validated by comparison with independent satellite measurements from HALOE (Version 19), SAGE II (Version 6.2), and POAM III (V2). Availability of MIPAS data were limited to the validation reference data set from July 2002 to December 2002. Between 100 hPa and 10 hPa (15-30 km) good agreement between MIPAS and the three satellite instruments to within the combined error of 15 (POAM III) to 25(HALOE) has been found. Above 30 km (below 10 hPa) a positive bias of up to 20% with respect to the other satellites has been observed. In the lowermost stratosphere root-mean-squared scatter of the observed differences increases dramatically (above 100 hPa with HALOE and POAM, and above 50 hPa with SAGE II). -
Article: First results of ozone profiles between 35 and 65km retrieved from SCIAMACHY limb spectra and observations of ozone depletion during the solar proton events in October/November 2003
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ABSTRACT: Ozone density profiles between 35 and 65 km altitude are derived from scattered sunlight limb radiance spectra measured by the SCIAMACHY instrument on the Envisat satellite. The method is based on the inversion of normalized limb radiance profiles in the Hartley absorption bands of ozone at selected wavelengths between 250 and 310 nm. It employs a non-linear Newtonian iteration version of Optimal Estimation (OE) coupled with the radiative transfer model SCIARAYS. The limb scatter technique combined with a classical OE retrieval in the short-wave UV-B and long-wave UV-C delivers reliable results as shown by a first comparison with MIPAS V4.61 profiles yielding agreement within 10% between 38 and 55 km. An overview of the methodology and an initial error analysis are presented. Furthermore the effect of the solar proton storm between 28 October and 6 November 2003 on the ozone concentration profiles is shown. They indicate large depletion of ozone of about 60% at 50 km in the Northern hemisphere, a weaker depletion in the Southern hemisphere and a dependence of the depletion on the Earth’s magnetic field.Advances in Space Research. -
Article: Validation of ENVISAT trace gas data products by comparison with @! GOME/ERS-2 and other satellite sensors.
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Article: Significance of the Polar Frontal Zone for large-sized diatoms and new production during summer in the Atlantic sector of the Southern Ocean
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ABSTRACT: The chlorophyll a (chl a) biomass and primary production of three phytoplankton size fractions were estimated in the Atlantic sector of the Southern Ocean from 12 December 1995 to 20 January 1996. Elevated concentrations of chl a, primary production, and contribution of microplankton (>20 μm) coincided with dominance by large or long-chained diatoms (Thalassiothrix spp., Pseudonitzschia lineola, and Chaetoceros spp.) in the Polar Frontal Zone (PFZ, 49.5°S–52°S). Vertically resolved assimilation numbers (i.e. primary production normalized to chl a) and intrinsic growth rates of microplankton were much lower at high-biomass stations of the Northern Polar Frontal Zone (NPFZ) than in adjacent waters. Silicic acid appeared to be the proximal factor limiting the growth and yield of resident diatoms in the NPFZ. A carbon budget showed that, during the sampling period, diatom dominance at high-biomass sites was associated with near-steady-state conditions. This system exhibited a low POC sinking flux relative to total primary production, despite strong dominance by microplankton. South of 52°S, total chl a and primary production were generally low, but increased sharply in a mixed Phaeocystis-diatom bloom that extended from 61°S to 65°S in the Seasonal Ice Zone (SIZ). We estimated that the PFZ contributes from 37% to 67% of the total open-water new production in the Southern Ocean near the Greenwich meridian, depending on whether blooms occur or not in the SIZ.Deep Sea Research Part II: Topical Studies in Oceanography. -
Article: Towards validation of SCIAMACHY lunar occultation NO2 vertical profiles
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ABSTRACT: Vertical profiles of stratospheric nitrogen dioxide (NO2) have been retrieved from moderate resolution lunar occultation transmission spectra measured by Scanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) on board the European Environmental Satellite (ENVISAT). These measurements were taken over the high southern latitude of 50°–90° during the period of 2003–2005. To assess the accuracy of the retrieved NO2 profiles, the SCIAMACHY nighttime NO2 profiles were compared with NO2 profiles retrieved from sunrise solar occultation spectra measured by the Halogen Occultation Experiment (HALOE) and the Stratospheric Aerosol and Gas Experiments II (SAGE II) using a photochemical correction model. The validation results show good agreement of SCIAMACHY lunar occultation NO2 with scaled HALOE and SAGE II profiles. The relative mean differences (rmd) with scaled HALOE profiles are within −13% to +5% and standard deviations (rms) of the relative differences are within 3–19% between 25 and 38 km. The rmd and rms with scaled SAGE II NO2 profiles are in the range of −9 to +7 and 10–17% respectively between 22 and 39 km.Advances in Space Research. -
Article: Comparison of total ozone from the satellite instruments GOME and TOMS with measurements from the Dobson network 1996-2000
Atmospheric Chemistry and Physics. 3:1409-1419. -
Article: Lunar occultation with SCIAMACHY: First retrieval results
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ABSTRACT: Scanning imaging absorption spectrometer for atmospheric chartography (SCIAMACHY) is a moderate resolution imaging spectrometer on board the environmental satellite (ENVISAT) launched in March 2002. SCIAMACHY has eight channels, covering a spectral range from 240 to 2380 nm and observes the Earth’s atmosphere in nadir, limb, and occultation geometries. From SCIAMACHY lunar occultation measurements, nighttime vertical profiles of O3 and NO2 have been retrieved over the southern hemisphere (60°–90°S) using the optimal estimation method. The first preliminary validation of retrieved O3 profiles with halogen occultation experiment and comparisons with stratospheric aerosol and gas experiment III (SAGE III), and Michelson interferometer for passive atmospheric sounding (MIPAS) O3 profiles were carried out. In addition, the retrieved NO2 profiles were compared to SAGE III and MIPAS results. The results of these preliminary validation and comparisons give confidence that reasonable scientific data products (trace gas profiles) can be derived from SCIAMACHY spectroscopic lunar occultation data.Advances in Space Research. -
Conference Proceeding: Sciamachy Ozone Profile Validation
Second Workshop on the Atmospherice Chemistry Validation (ACVE-2), Frascati, Italy 3-7 May 2004;
