| 1. |
- Khosrawi, Farahnaz, 1971-, et al.
(författare)
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Evaluation of CLaMS, KASIMA and ECHAM5/MESSy1 simulations in the lower stratosphere using observations of Odin/SMR and ILAS/ILAS-II
- 2009
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 9:15, s. 5759-5783
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Tidskriftsartikel (refereegranskat)abstract
- 1-year data sets of monthly averaged nitrous oxide (N2O) and ozone (O3) derived from satellite measurements were used as a tool for the evaluation of atmospheric photochemical models. Two 1-year data sets, one solar occultation data set derived from the Improved Limb Atmospheric Spectrometer (ILAS and ILAS-II) and one limb sounding data set derived from the Odin Sub-Millimetre Radiometer (Odin/SMR) were employed. Here, these data sets are used for the evaluation of two Chemical Transport Models (CTMs), the Karlsruhe Simulation Model of the Middle Atmosphere (KASIMA) and the Chemical Lagrangian Model of the Stratosphere (CLaMS) as well as for one Chemistry-Climate Model (CCM), the atmospheric chemistry general circulation model ECHAM5/MESSy1 (E5M1) in the lower stratosphere with focus on the Northern Hemisphere. Since the Odin/SMR measurements cover the entire hemisphere, the evaluation is performed for the entire hemisphere as well as for the low latitudes, midlatitudes and high latitudes using the Odin/SMR 1-year data set as reference. To assess the impact of using different data sets for such an evaluation study we repeat the evaluation for the polar lower stratosphere using the ILAS/ILAS-II data set. Only small differences were found using ILAS/ILAS-II instead of Odin/SMR as a reference, thus, showing that the results are not influenced by the particular satellite data set used for the evaluation. The evaluation of CLaMS, KASIMA and E5M1 shows that all models are in agreement with Odin/SMR and ILAS/ILAS-II. Differences are generally in the range of ±20%. Larger differences (up to −40%) are found in all models at 500±25 K for N2O mixing ratios greater than 200 ppbv, thus in air masses of tropical character. Generally, the largest differences were found for the tropics and the lowest for the polar regions. However, an underestimation of polar winter ozone loss was found both in KASIMA and E5M1 both in the Northern and Southern Hemisphere.
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| 2. |
- Khosrawi, Farahnaz, et al.
(författare)
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Monthly averaged ozone and nitrous oxide from the Improved Limb Atmospheric Spectrometer (ILAS) in the Northern and Southern Hemisphere polar regions
- 2004
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Ingår i: Journal of Geophysical Research. ; 109
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Tidskriftsartikel (refereegranskat)abstract
- Northern and southern hemispheric averaged ozone (O3) and nitrous oxide (N2O) measured by the Improved Limb Atmospheric Spectrometer (ILAS) were used to examine photochemical and dynamical changes in high-latitude O3 distributions. Using correlations of O3 versus N2O, the ILAS data are organized monthly in both hemispheres by partitioning these data into equal bins of altitude or potential temperature. The resulting families of curves help to differentiate O3 changes due to photochemistry from those due to transport. Our study extends the work of Proffitt et al. [2003] for the Northern Hemisphere to the Southern Hemisphere. Further, our study confirms and extends their results for the Northern Hemisphere by applying their analysis to a significantly greater altitude range. As in the Northern Hemisphere, the families of curves for the altitude, and potential temperature bins in the Southern Hemisphere are separated and generally do not cross. In both hemispheres a better separation is found for the potential temperature binning. In the Southern Hemisphere November and December data, preserved photochemical O3 loss is evident in the lower stratosphere. Further, summer ozone loss is evident in the Southern Hemisphere from January to March. In the Arctic, ongoing photochemical O3 loss is evident in the Northern Hemisphere spring data. While at higher altitudes the correlation between N2O and O3 is generally positive (increasing N2O with increasing O3), at lower levels the correlation is negative. This change of correlation from positive to negative can be interpreted in terms of photochemical and dynamical processes. Strong descent causes a steepening of the positively correlated curves, while the curves change their slope from positive to negative if photochemical destruction of O3 is present and descent is weak. The level of slope change is also photochemically influenced and therefore changes with season. Data sets such as the one derived here may be useful for testing atmospheric models and for identifying future changes in stratospheric ozone.
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| 3. |
- Khosrawi, Farahnaz, et al.
(författare)
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Monthly averages of nitrous oxide and ozone for the Northern and Southern Hemisphere high latitudes: A ``one-year climatology'' derived from ILAS/ILAS-II observations
- 2006
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Ingår i: Journal of Geophysical Research. ; 111:D11S11
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Tidskriftsartikel (refereegranskat)abstract
- Correlations of ozone (O3) and nitrous oxide (N2O) have been suggested as a tool for validating photochemical models and as a reference for estimating high-latitude ozone loss. However, so far no analysis of ozone-tracer relations is available that provides agood temporal coverage during all months. Here we combine measurements from the Improved Limb Atmospheric Spectrometers (ILAS/ILAS-II) to derive an O3/N2O climatology for the high-latitude regions in the Northern and Southern Hemisphere foreach month of the year, thus providing a complete seasonal cycle. ILAS and ILAS-II operated on board the Advanced Earth Observing Satellite (ADEOS/ADEOS-II), and both instruments use the solar occultation technique. ILAS operated for 8 months in 1996/1997,and ILAS-II operated for 7 months in 2003. The ILAS-II measurements cover the months that are not available from ILAS. The ILAS/ILAS-II correlations of ozone versus nitrous oxide are organized monthly in both hemispheres by partitioning these data into equal bins of altitude or potential temperature. The resulting families of curves allow separation of ozone changes due to photochemistry from those due to transport. The combined ILAS/ILAS-II data set corroborates earlier findings that the families of O3/N2O curves are separated and generally do not cross and further that the separation is much clearer for the potential temperature binning than for the altitude binning. The much clearer separation for the potential temperature binning is due to transport being predominantly isentropic. Thus these curves are particularly suitable for the validation of photochemical models. The seasonal cycle of O3/N2O distributions in the Northern and Southern Hemisphere high latitudes is found to be rather different. In the Southern Hemisphere, O3/N2O distributions are influenced by the strong chemical ozone loss in the Antarctic vortex and by a much longer duration of the polar vortex. In the Northern Hemisphere, diabatic descent is much more pronounced. Solely during the setup phase of the polar vortex the N2O/O3 distributions in the two hemispheres are rather similar.
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| 4. |
- Suito, Hideaki, et al.
(författare)
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Influence of Oxide Particles and Residual Elements on Microstructure and Toughness in the Heat-Affected Zone of Low-Carbon Steel Deoxidized with Ti and Zr
- 2011
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 51:7, s. 1151-1162
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Tidskriftsartikel (refereegranskat)abstract
- The microstructure and toughness in Fe-0.04%C-1.85%Mn-0.03%Si-0.018%Nb steel deoxidized with Ti and Zr have been studied as functions of particle characteristics, austenite grain size and soluble Ti and Zr contents using a simulated HAZ (heat affected zone) thermal cycle (peak temperature, 1 400 degrees C; peak holding time, 60 s; time of cooling from 800 to 500 degrees C, 70 s) and submerged arc welding (heat input of 15 kJ/mm), respectively. Microstructures were studied in samples containing 1.0 to 1.5 mu m-diameter oxide particles numbering 500 to 2 000 mm(-2) and with a soluble oxygen content of 10 to 30 ppm (measured before casting) and soluble Ti and Zr contents of 50-150 ppm. The gamma grain size after HAZ thermal cycle in the range between 200 and 600 mu m is controlled by pinning and solute drag. Small gamma grain size below 300 mu m was obtained with high soluble Ti and Zr contents of 110-160 ppm, whereas large gamma grain size above 300 mu m was obtained with low soluble Ti and Zr contents of 60-110 ppm. Two types of microstructures that showed high Charpy absorbed energy (vE(-10 degrees C)= 150-250 J and vE(-50 degrees C)= 50-150 J) were observed independent of gamma grain size: One is acicular ferrite and a small amount of grain boundary ferrite (GBF) and ferrite side plate (FSP) and the other is GBF, FSP and granular bainitic ferrite. It was observed that low vE(T) values are attributed to the formation of porosity, large-size particles, carbides (+nitrides) and lathe bainitic ferrite.
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