| 1. |
- Brohede, Samuel, 1977, et al.
(author)
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Internal consistency in the Odin stratospheric ozone products
- 2007
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In: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1275-1285
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Journal article (peer-reviewed)abstract
- The two independent instruments on the Odin satellite, the Optical Spectrograph and Infrared Imaging System (OSIRIS) and the Sub-Millimetre Radiometer (SMR) produce atmospheric profiles of various atmospheric species including stratospheric ozone. Comparisons are made between OSIRIS version 3.0 and SMR version 2.1 ozone data to evaluate the consistency of the Odin ozone data sets. Results show good agreement between OSIRIS and SMR in the range 25–40 km, where systematic differences are less than 15% for all latitudes and seasons. Larger systematic differences are seen below 25 km, which can be explained by the increase of various error sources and lower signals. The random differences are between 20–30% in the middle stratosphere. Differences between Odin up-scans and down-scans or AM and PM are insignificant in the middle stratosphere. Furthermore, there is little variation from year to year, but a slight positive trend in the differences (OSIRIS minus SMR) of 0.045 ppmv/year at 30 km over validation period (2002–2006). The fact that the two fundamentally different measurement techniques, (absorption spectroscopy of scattering sunlight and emission measurements in the sub-millimetre region) agree so well, provides confidence in the robustness of both techniques.
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| 2. |
- Haley, C. S., et al.
(author)
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Status of the Odin/OSIRIS stratospheric O3 and NO2 data products
- 2007
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In: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1177-1194
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Journal article (peer-reviewed)abstract
- This paper describes the status of the stratospheric ozone and nitrogen dioxide data products from the Optical Spectrograph and InfraRed Imager System (OSIRIS) instrument on the Odin satellite. The current version of the data products is 3.0, covering the period from November 2001 to the present. The O3 and NO2 retrieval methods are reviewed along with an overview of the error analyses and geophysical validation status.
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| 3. |
- Brohede, Samuel, 1977
(author)
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Satellite Limb-Scatter Observations of Stratospheric NO2 and O3 -Retrievals, Validation and Applications
- 2008
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Doctoral thesis (other academic/artistic)abstract
- Global observations of vertically resolved atmospheric constituents with high temporal and spatial sampling are crucial for various scientific assessments of ozone depletion and climate change. This thesis explains how such data can be retrieved from satellite limb-scatter observations. The main focus is stratospheric NO2 and O3 measured by the the Optical Spectrograph and Infra-Red Imager System (OSIRIS) aboard the Swedish satellite Odin, although the principles can be used for any similar instrument, for other gases and atmospheric regions. The entire process from detector photon counts to a validated operational data product is covered.Transformations of observed radiances to effective column densities for NO2 and Chappuis triplets for O3 in combination with a normalization, significantly reduces the sensitivity to aerosol, clouds, instrument effects and absolute calibration. A maximum a posteriori inversion method produces well behaved data and provides estimates of measurement uncertainty and vertical resolution for individual profiles. Credible data are generally found between 12 and 42 km with a vertical resolution of around 2 km and random uncertainties of about 5\% for O3 and 10\% for NO2. External comparisons reveal good agreement between 25 and 35 km and long-term stability. Sensitivity studies identify four major concerns; stray light contamination, inaccurate pointing, atmospheric inhomogeneities and clouds.Applications of OSIRIS data and the construction of global climatologies of NO2, O3 and NOy are also presented together with model comparisons which indicate inaccurate simulations of heterogeneous nitrogen processes.
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| 4. |
- Brohede, Samuel, 1977, et al.
(author)
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A stratospheric NO2 climatology from Odin/OSIRIS limb-scatter measurements
- 2007
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In: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1253-1274
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Journal article (peer-reviewed)abstract
- A climatology of stratospheric nitrogen dioxide (NO2), in terms of mean and standard deviation, as a function of latitude (5° bins); altitude (10–46 km in 2 km bins); local solar time (24 h); and month is constructed based on the Odin/OSIRIS limb-scattering data from 2002–2005. The measured profiles, given at specific local solar times, are scaled to all 24 h using a photochemical box model. The Odin orbit gives near global coverage around the equinoxes and hemispheric coverage elsewhere, due to lack of sunlight. The mean NO2 field at a specific local solar time involves high concentrations in the polar summer, peaking at around 25 km, with a negative equatorward gradient. Distinct high levels between 40–50° latitude at 30 km in the winter/spring hemisphere are also found, associated with the so-called {Noxon-cliff}. The diurnal cycle reveals the lowest NO2 concentrations just after sunrise and steep gradients at twilight. The 1σ standard deviation is generally quite low, around 20%, except for winter and spring high latitudes, where values are well above 50% and stretch through the entire stratosphere, a phenomenon probably related to the polar vortex. It is also found that NO2 concentrations are log-normally distributed. Comparisons to a climatology based on data from a (REPROBUS) chemical transport model for the same time period reveal relative differences below 20% in general, which is comparable to the estimated OSIRIS systematic uncertainty. Clear exceptions are the polar regions in winter/spring throughout the atmosphere and equatorial regions below 25 km, where OSIRIS is relatively higher by 40% and more. These discrepancies are most likely attributable to limitations of the model, but this has to be investigated further.
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