| 11. |
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| 12. |
- Baron, P., et al.
(författare)
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The level 2 research product algorithms for the superconducting submillimeter-wave limb-emission sounder (SMILES)
- 2011
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Ingår i: Atmospheric Measurement Techniques Discussions. - : Copernicus GmbH. - 1867-8610. ; 4:3, s. 3593-3645
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the algorithms of the level-2 research (L2r) processingchain developed for the Superconducting Submillimeter-Wave Limb-EmissionSounder (SMILES). The chain has been developed in parallel to the operationalchain for conducting researches on calibration and retrieval algorithms. L2rchain products are available to the scientific community. The objective ofversion 2 is the retrieval of the vertical distribution of trace gases in thealtitude range of 18-90 km. An theoretical error analysis is conducted toestimate the retrieval feasibility of key parameters of the processing:line-of-sight elevation tangent altitudes (or angles), temperature and O3 profiles. The line-of-sight tangent altitudes are retrievedbetween 20 and 50 km from the strong ozone (O3) line at 625.371 GHz,with low correlation with the O3 volume-mixing ratio and temperatureretrieved profiles. Neglecting the non-linearity of the radiometric gain inthe calibration procedure is the main systematic error. It is large for theretrieved temperature (between 5-10 K). Therefore, atmospheric pressure cannot be derived from the retrieved temperature, and, then, in the altituderange where the line-of-sight tangent altitudes are retrieved, the retrievedtrace gases profiles are found to be better represented on pressure levelsthan on altitude levels. The error analysis for the retrieved HOCl profiledemonstrates that best results for inverting weak lines can be obtained byusing narrow spectral windows. Future versions of the L2r algorithms willimprove the temperature/pressure retrievals and also provide information inthe upper tropospheric/lower stratospheric region (e.g., water vapor, icecontent, O3) and on stratospheric and mesospheric line-of-sight winds.
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| 13. |
- Baron, P., et al.
(författare)
-
The Level 2 research product algorithms for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)
- 2011
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 4, s. 2105-2124
-
Tidskriftsartikel (refereegranskat)abstract
- This paper describes the algorithms of the level-2 research (L2r) processing chain developed for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). The chain has been developed in parallel to the operational chain for conducting researches on calibration and retrieval algorithms. L2r chain products are available to the scientific community. The objective of version 2 is the retrieval of the vertical distribution of trace gases in the altitude range of 18–90 km. A theoretical error analysis is conducted to estimate the retrieval feasibility of key parameters of the processing: line-of-sight elevation tangent altitudes (or angles), temperature and ozone profiles. While pointing information is often retrieved from molecular oxygen lines, there is no oxygen line in the SMILES spectra, so the strong ozone line at 625.371 GHz has been chosen. The pointing parameters and the ozone profiles are retrieved from the line wings which are measured with high signal to noise ratio, whereas the temperature profile is retrieved from the optically thick line center. The main systematic component of the retrieval error was found to be the neglect of the non-linearity of the radiometric gain in the calibration procedure. This causes a temperature retrieval error of 5–10 K. Because of these large temperature errors, it is not possible to construct a reliable hydrostatic pressure profile. However, as a consequence of the retrieval of pointing parameters, pressure induced errors are significantly reduced if the retrieved trace gas profiles are represented on pressure levels instead of geometric altitude levels. Further, various setups of trace gas retrievals have been tested. The error analysis for the retrieved HOCl profile demonstrates that best results for inverting weak lines can be obtained by using narrow spectral windows.
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| 14. |
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| 15. |
- Jones, N., et al.
(författare)
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Stratomesospheric CO measured by a ground-based Fourier Transform Spectrometer over Poker Flat, Alaska: Comparisons with Odin/SMR and a 2-D model
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112:D20
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Tidskriftsartikel (refereegranskat)abstract
- The interseasonal variability of stratomesospheric CO is reported from Poker Flat, Alaska, using spectra from a ground-based Fourier Transform Spectrometer (gb-FTS) for the time period from 2000 to 2004. The CO spectra were analyzed using an optimal estimation technique that separates the tropospheric and stratospheric/mesospheric components into partial columns. The distribution of CO in the polar winter is such that the gb-FTS retrieved partial column is weighted to the mesosphere. The gb-FTS data are compared with measurements of partial column CO from the Sub-Millimeter Radiometer on board the Odin satellite and shown to be in very good agreement despite the relatively small sample size. The mean difference of the two data sets indicates a small positive bias (7.6 +/- 6%) in favor of the Odin data, with a correlation coefficient, r(2) = 0.91. The gb-FTS data indicate that there is a strong seasonal dependence of the CO partial column that is consistent with known winter polar thermospheric descent of CO enriched air. Year-to-year variability is explained in terms of mesospheric wind dynamics, which show 2004 and components of 2002 were affected by earlier than expected breakdown (30 +/- 13 d) of the winter polar circulation compared with 2000 to 2003. Finally, the measured CO data is compared with a 2-D chemical transport model that gives support to the idea that springtime polar mesospheric CO is driven by meridional winds.
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| 16. |
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| 17. |
- Buyanova, Irina A., et al.
(författare)
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Effect of momentum relaxation on exciton spin dynamics in diluted magnetic semiconductor ZnMnSe CdSe superlattices
- 2005
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 71:16
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Tidskriftsartikel (refereegranskat)abstract
- cw hot photoluminescence (PL) complemented by transient PL measurements is employed to evaluate momentum and spin relaxation of heavy hole (HH) excitons in ZnMnSe CdSe superlattices. The rate of acoustic-phonon assisted momentum relaxation is concluded to be comparable to the total rate of exciton decay processes, about (2-3) × 1010 s-1, independent of applied magnetic fields. In magnetic fields when the Zeeman splitting ? of the exciton states is below the energy of the longitudinal optical (LO) phonon (?LO), a surprisingly strong suppression of spin relaxation rate from the bottom of the upper spin band is observed, which becomes comparable to that of momentum scattering via acoustic phonons. On the other hand, dramatic acceleration of the spin relaxation process by more than one order of magnitude is found for the excitons with a high momentum K. The findings are interpreted as being due to electron and hole spin flip processes via exchange interaction with isolated Mn2+ ions. Experimental evidence for the efficient interaction between the hot excitons and Mn impurities is also provided by the observation of spin flip transitions within Mn2+ - Mn2+ pairs that accompany the momentum relaxation of the hot HH excitons. In higher magnetic fields ?= ?LO, abrupt shortening of the spin flip time is observed. It indicates involvement of a new and more efficient spin relaxation process and is attributed to direct LO-assisted exciton spin relaxation with a subpicosecond spin relaxation time. © 2005 The American Physical Society.
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