| 1. |
- Brohede, Samuel, 1977, et al.
(författare)
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Internal consistency in the Odin stratospheric ozone products
- 2007
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Ingår i: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1275-1285
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Tidskriftsartikel (refereegranskat)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. |
- Jones, Ashley, 1977, et al.
(författare)
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Evolution of stratospheric ozone and water vapour time series studied with satellite measurements
- 2009
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9, s. 6055-6075
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Tidskriftsartikel (refereegranskat)abstract
- The long term evolution of stratospheric ozone and water vapour has been investigated by extending satellite time series to April 2008. For ozone, we examine monthly average ozone values from various satellite data sets for nine latitude and altitude bins covering 60° S to 60° N and 20–45 km and covering the time period of 1979–2008. Data are from the Stratospheric Aerosol and Gas Experiment (SAGE I+II), the HALogen Occultation Experiment (HALOE), the Solar BackscatterUltraViolet-2 (SBUV/2) instrument, the Sub-Millimetre Radiometer (SMR), the Optical Spectrograph InfraRed Imager System (OSIRIS), and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartograpY (SCIAMACHY). Monthly ozone anomalies are calculated by utilising a linear regression model, which also models the solar, quasi-biennial oscillation (QBO), and seasonal cycle contributions. Individual instrument ozone anomalies are combined producing an all instrument average. Assuming a turning point of 1997 and that the all instrument average is represented by good instrumental long term stability, the largest statistically significant ozone declines (at two sigma) from 1979–1997 are seen at the mid-latitudes between 35 and 45 km, namely −7.2%±0.9%/decade in the Northern Hemisphere and −7.1%±0.9%/in the Southern Hemisphere. Furthermore, for the period 1997 to 2008 we find that the same locations show the largest ozone recovery (+1.4% and +0.8%/decade respectively) compared to other global regions, although the estimated trend model errors indicate that the trend estimates are not significantly different from a zero trend at the 2 sigma level. An all instrument average is also constructed from water vapour anomalies during 1991–2008, using the SAGE II, HALOE, SMR, and the Microwave Limb Sounder (Aura/MLS) measurements. We report that the decrease in water vapour values after 2001 slows down around 2004–2005 in the lower tropical stratosphere (20–25 km) and has even shown signs of increasing until present. We show that a similar correlation is also seen with the temperature measured at 100 hPa during this same period.
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| 3. |
- RÖSEVALL, JOHN, 1977, et al.
(författare)
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A study of ozone depletion in the 2004/2005 Arctic winter based on data from Odin/SMR and Aura/MLS
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113:D13
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Tidskriftsartikel (refereegranskat)abstract
- Ozone depletion in the colder than average 2004/2005 Arctic polar vortex is mapped and quantified using ozone profiles from two limb sounding satellite instruments, the Earth Observing System Microwave Limb Sounder (Aura/MLS) and the Odin Sub-Millimetre Radiometer (Odin/SMR). Profiles of chemically inert nitrous oxide (N(2)O) are used to trace vertical transport during the winter. Two methods are used for estimating the vortex average ozone losses north of 67 degrees equivalent latitude. In a first step, the time evolution of ozone mixing ratios is described on N(2)O isopleths. Maximum ozone depletion is found on the 100 ppbv and 150 ppbv N(2)O isopleths (located in the 430-460 K potential temperature range in mid-March 2005) where vortex average ozone depletion totalled 1.0-1.1 ppmv for Aura/MLS and 0.7-0.9 ppmv for Odin/SMR. Second, ozone profiles from Aura/MLS and Odin/SMR are assimilated into the DIAMOND isentropic transport model. Ozone depletion is estimated by comparing assimilated fields to ozone fields passively transported from 1 January. On the 450 K potential temperature level, the Aura/MLS ozone fields indicate 0.9-1.3 ppmv vortex-averaged ozone depletion while the Odin/SMR fields indicate 0.6-0.9 ppmv depletion. The uncertainty depends mainly on the rates of cross-isentropic transport used in the study. The ozone depletion estimates in this study are lower than previously published estimates. The discrepancies to some studies can be attributed to the more adequate treatment of an ozone poor region that is found in the central polar vortex in the early winter.
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| 4. |
- Brohede, Samuel, 1977, et al.
(författare)
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A stratospheric NO2 climatology from Odin/OSIRIS limb-scatter measurements
- 2007
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Ingår i: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1253-1274
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Tidskriftsartikel (refereegranskat)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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| 5. |
- Brohede, Samuel, 1977, et al.
(författare)
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Odin stratospheric proxy NOy measurements and climatology
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:19, s. 5731-5754
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Tidskriftsartikel (refereegranskat)abstract
- Five years of OSIRIS (Optical Spectrograph and InfraRed Imager System) NO2 and SMR (Sub-millimetre and Millimetre Radiometer) HNO3 observations from the Odin satellite, combined with data from a photochemical box model, have been used to construct a stratospheric proxy NOy data set including the gases: NO, NO2, HNO3, 2×N2O5 and ClONO2. This Odin NOy climatology is based on all daytime measurements and contains monthly mean and standard deviation, expressed as mixing ratio or number density, as function of latitude or equivalent latitude (5° bins) on 17 vertical layers (altitude, pressure or potential temperature) between 14 and 46 km. Comparisons with coincident NOy profiles from the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) instrument were used to evaluate several methods to combine Odin observations with model data. This comparison indicates that the most appropriate merging technique uses OSIRIS measurements of NO2, scaled with model NO/NO2 ratios, to estimate NO. The sum of 2×N2O5 and ClONO2 is estimated from uncertainty-based weighted averages of scaled observations of SMR HNO3 and OSIRIS NO2. Comparisons with ACE-FTS suggest the precision (random error) and accuracy (systematic error) of Odin NOy profiles are about 15% and 20%, respectively. Further comparisons between Odin and the Canadian Middle Atmosphere Model (CMAM) show agreement to within 20% and 2 ppb throughout most of the stratosphere except in the polar vortices. The combination of good temporal and spatial coverage, a relatively long data record, and good accuracy and precision make this a valuable NOy product for various atmospheric studies and model assessments.
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| 6. |
- Brohede, Samuel, 1977
(författare)
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Satellite Limb-Scatter Observations of Stratospheric NO2 and O3 -Retrievals, Validation and Applications
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)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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| 7. |
- Brohede, Samuel, 1977, et al.
(författare)
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Validation of Odin/OSIRIS stratospheric NO2 profiles
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:D07310
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the validation study of stratospheric NO2 profiles retrieved from Odin/OSIRIS measurements of limb-scattered sunlight (version 2.4). The Optical Spectrograph and Infrared Imager System (OSIRIS) NO2 data set is compared to coincident solar occultation measurements by the Halogen Occultation Experiment (HALOE), Stratospheric Aerosol and Gas Experiment (SAGE) II, SAGE III, and Polar Ozone and Aerosol Measurement (POAM) III during the 2002–2004 period. Comparisons with seven Systeme d'Analyse par Observation Zenithal (SAOZ) balloon measurements are also presented. All comparisons show good agreement, with differences, both random and systematic, of less than 20% between 25 km and 35 km. Inconsistencies with SAGE III below 25 km are found to be caused primarily by diurnal effects from varying NO2 concentrations along the SAGE III line-of-sight. On the basis of the differences, the OSIRIS random uncertainty is estimated to be 16% between 15 km and 25 km, 6% between 25 km and 35 km, and 9% between 35 km and 40 km. The estimated systematic uncertainty is about 22% between 15 and 25 km, 11–21% between 25 km and 35 km, and 11–31% between 35 km and 40 km. The uncertainties for AM (sunrise) profiles are generally largest and systematic deviations are found to be larger at equatorial latitudes. The results of this validation study show that the OSIRIS NO2 profiles are well behaved, with reasonable uncertainty estimates between 15 km and 40 km. This unique NO2 data set, with more than hemispheric coverage and high vertical resolution will be of particular interest for studies of nitrogen chemistry in the middle atmosphere, which is closely linked to ozone depletion.
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| 8. |
- Haley, C. S., et al.
(författare)
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Status of the Odin/OSIRIS stratospheric O3 and NO2 data products
- 2007
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Ingår i: Canadian Journal of Physics. - 0008-4204 .- 1208-6045. ; 85:11, s. 1177-1194
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Tidskriftsartikel (refereegranskat)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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| 9. |
- Kerzenmacher, T., et al.
(författare)
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Validation of NO2 and NO from the Atmospheric Chemistry Experiment (ACE)
- 2008
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 8:19, s. 5801--5841-
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Tidskriftsartikel (refereegranskat)abstract
- Vertical profiles of NO2 and NO have been obtained from solar occultation measurements by the Atmospheric Chemistry Experiment (ACE), using an infrared Fourier Transform Spectrometer (ACE-FTS) and (for NO2) an ultraviolet-visible-near-infrared spectrometer, MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). In this paper, the quality of the ACE-FTS version 2.2 NO2 and NO and the MAESTRO version 1.2 NO2 data are assessed using other solar occultation measurements (HALOE, SAGE II, SAGE III, POAM III, SCIAMACHY), stellar occultation measurements (GOMOS), limb measurements (MIPAS, OSIRIS), nadir measurements (SCIAMACHY), balloon-borne measurements (SPIRALE, SAOZ) and ground-based measurements (UV-VIS, FTIR). Time differences between the comparison measurements were reduced using either a tight coincidence criterion, or where possible, chemical box models. ACE-FTS NO2 and NO and the MAESTRO NO2 are generally consistent with the correlative data. The ACE-FTS and MAESTRO NO2 volume mixing ratio (VMR) profiles agree with the profiles from other satellite data sets to within about 20% between 25 and 40 km, with the exception of MIPAS ESA (for ACE-FTS) and SAGE II (for ACE-FTS (sunrise) and MAESTRO) and suggest a negative bias between 23 and 40 km of about 10%. MAESTRO reports larger VMR values than the ACE-FTS. In comparisons with HALOE, ACE-FTS NO VMRs typically (on average) agree to ±8% from 22 to 64 km and to +10% from 93 to 105 km, with maxima of 21% and 36%, respectively. Partial column comparisons for NO2 show that there is quite good agreement between the ACE instruments and the FTIRs, with a mean difference of +7.3% for ACE-FTS and +12.8% for MAESTRO.
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| 10. |
- Randall, C. E., et al.
(författare)
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Stratospheric effects of energetic particle precipitation in 2003-2004
- 2005
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Ingår i: Geophysical Research Letters. - 1944-8007 .- 0094-8276. ; 32:5, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- Upper stratospheric enhancements in NOx (NO and NO2) were observed at high northern latitudes from March through at least July of 2004. Multi-satellite data analysis is used to examine the temporal evolution of the enhancements, to place them in historical context, and to investigate their origin. The enhancements were a factor of 4 higher than nominal at some locations, and are unprecedented in the northern hemisphere since at least 1985. They were accompanied by reductions in O-3 of more than 60% in some cases. The analysis suggests that energetic particle precipitation led to substantial NOx production in the upper atmosphere beginning with the remarkable solar storms in late October 2003 and possibly persisting through January. Downward transport of the excess NOx, facilitated by unique meteorological conditions in 2004 that led to an unusually strong upper stratospheric vortex from late January through March, caused the enhancements.
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