B.Sc. (High Honours) Environmental Science - Carleton University (1997)
PhD Earth and Space Science - York University (2001)
mailing address (Environment Canada):
4905 Dufferin Street
Toronto, ON
M3H 5T4
Canada
e-mail: christopher.sioris@ec.gc.ca
tel: (416) 739-4929
Research interests: Raman spectroscopy, radiative transfer including polarization, atmospheric correction, remote sensing of environmental change, measurements of trace gas profiles (ozone, NO2, BrO, OClO, H2O) from limb scatter and solar occultation, tropospheric vertical column maps of nitrogen dioxide.
My Ph.D. work was related to the Ring effect,
named after James Ring who discovered the effect with J. R. Grainger in
the early sixties. The Ring effect is the filling-in of solar and terrestrial
absorption lines in scattered skylight spectra due to rotational Raman
Scattering (RRS). This effect interferes with measurements of trace gases (eg. BrO, OClO) in skylight, despite
being frequently neglected. The Ring effect is particularly important in
the UV/vis at high resolution, and at scattering angles near 90°
because rotational Raman scattering has a more isotropic phase function than Rayleigh scattering.
An iterative backward model which removes the Ring effect from sky spectra has been developed. This model has outperformed the technique of treating the Ring effect as an absorber
with its own DOAS spectrum (measured or modelled). This is available
in the Canadian Journal of Physics. Stay posted by bookmarking this page.
Refereed publications
2. C. E. Sioris and W. F. J. Evans, Impact of rotational Raman scattering in the O2 A band, Geophys. Res. Lett., 27, 4085, 2000.
3. C. E. Sioris, W. F. J. Evans, R. L. Gattinger, I. C. McDade, D. Degenstein, E. J., Llewellyn, Ground-based Ring effect measurements with the OSIRIS DM, Can. J. Phys., 80, 483-491, 2002.
4. C. E. Sioris and W. F. J. Evans, Modeling higher order radiation fields with iterated integrals of phase functions, J. Quant. Spectrosc. Radiat. Transfer, 72-3, 227-236, 2002.
5. D. Murtagh, U. Frisk, F. Merino, M. Ridal, A. Jonsson, J. Stegman, G. Witt, P. Eriksson, C. Jiménez, G. Mégie, J. de la Noë, P. Ricaud, P. Baron, J. R. Pardo, A. Hauchcorne, E. J. Llewellyn, D. A. Degenstein, R. L. Gattinger, N. D. Lloyd, W. F. J. Evans, I. C. McDade, C. S. Haley, C. Sioris, C. von Savigny, B. H. Solheim, J. C. McConnell, K. Strong, E. H. Richardson, G. W. Leppelmeier, E. Kyrölä, H. Auvinen, and L. Oikarinen, An overview of the Odin mission, Can. J. Phys., 80, 309-319, 2002.
6. C. E. Sioris, G. Bazalgette Courrèges-Lacoste, M.-P. Stoll, Filling in of Fraunhofer lines by plant fluorescence: Simulations for a nadir-viewing satellite-borne instrument, J. Geophys. Res., 108(D4), 4133, doi:10.1029/2001JD001321, 2003.
7. C. E. Sioris, C. S. Haley, C. A. McLinden, C. von Savigny, I. C. McDade, J. C. McConnell, W. F. J. Evans, N. D. Lloyd, E. J. Llewellyn, K. V. Chance, T. P. Kurosu, D. Murtagh, U. Frisk, K. Pfeilsticker, H. Bösch, F. Weidner, K. Strong, J. Stegman, and G. Mégie, Stratospheric profiles of nitrogen dioxide observed by OSIRIS on the Odin satellite, J. Geophys. Res., 108(D7), 4215, doi:10.1029/2002JD002672, 2003.
8. C. von Savigny, C. S. Haley, C. E. Sioris, I. C. McDade, E. J. Llewellyn, D. Degenstein, W. F. J. Evans, R. L. Gattinger, E. Griffioen, E. Kyrölä, N. D. Lloyd, J. C. McConnell, C. A. McLinden, G. Mégie, D. P. Murtagh, B. Solheim, and K. Strong, Stratospheric O3 profiles retrieved from limb scattered sunlight radiance spectra measured by the OSIRIS instrument on the Odin satellite, Geophys. Res. Lett., 30(14), 1755, doi:10,1029/2002GL016401, 2003.
9. C. E. Sioris, T. P. Kurosu, R. V. Martin, and K. Chance, Stratospheric and tropospheric NO2 observed by SCIAMACHY: First results, Adv. Space Res., 34(4), 780-785, 2004.
10. E. J. Llewellyn, N. D. Lloyd, D. A. Degenstein, R. L. Gattinger, S. V. Petelina, A. E. Bourassa, J. T. Wiensz, E. V. Ivanov, I. C. McDade, B. H. Solheim, J. C. McConnell, C. S. Haley, C. von Savigny, C. E. Sioris, et al., The OSIRIS Instrument on the Odin Spacecraft, Can. J. Phys., 82, 411-422, 2004.
11. C. S. Haley, S. M. Brohede, C. E. Sioris, D. P. Murtagh, I. C. McDade, E. J. Llewellyn, A. Bazureau, and F. Goutail, DOAS retrievals of stratospheric O3 and NO2 from Odin/OSIRIS limb-scattered sunlight measurements, J. Geophys. Res.,109, D16303, doi:10.1029/2004JD004588, 2004.
12. C. S. Haley, C. von Savigny, S. Brohede, C. E. Sioris, I. C. McDade, E. J. Llewellyn, D. P. Murtagh, A comparison of methods for retrieving stratospheric ozone profiles from OSIRIS limb-scatter measurements, Adv. Space Res., 34(4), 769-774, 2004.
13. K. Chance, T. P. Kurosu, and C. E. Sioris, Undersampling correction for array detector-based satellite spectrometers, Appl. Opt., 44, 1296-1304, 2005.
14. C. von Savigny, I. C. McDade, E. Griffioen, C. S. Haley, C. E. Sioris, and E. J. Llewellyn, Sensitivity studies and first validation of stratospheric ozone profile retrievals from Odin/OSIRIS observations of limb scattered solar radiation, Can J. Phys., 83, 957-972, 2005.
15. X. Liu, C.E. Sioris, K.V. Chance, T.P. Kurosu, M.J. Newchurch, R.V. Martin, and P.I. Palmer, Mapping tropospheric ozone profiles from an airborne UV/Visible spectrometer, Appl. Opt., 44, 3312-3319, 2005.
16. R. J. Salawitch, D. K. Weisenstein, L. J. Kovalenko, C. E. Sioris, P. O. Wennberg, K. Chance, M. K. W. Ko, and C. A. McLinden, Sensitivity of ozone to bromine in the lower stratosphere, Geophys. Res. Lett., 32, L05811, doi:10.1029/2004GL021504, 2005.
17. C. E. Randall, V. L. Harvey, G. L. Manney, Y. Orsolini, M. Codrescu, C. Sioris, S. Brohede, C. S. Haley, L. L. Gordley, J. M. Zawodny, J. M. Russell III, Stratospheric effects of energetic particle precipitation in 2003-2004, Geophys. Res. Lett., 32, L05802, doi:10.1029/2004GL022003, 2005.
18. P. Ricaud, F. Lefèvre, G. Berthet, D. Murtagh, E. J. Llewellyn, G. Mégie, E. Kyrölä, G. W. Leppelmeier, H. Auvinen, C. Boonne, S. Brohede, D. A. Degenstein, J. de La Noë, E. Dupuy, L. El Amraoui, P. Eriksson, W. F. J. Evans, U. Frisk, R. L. Gattinger, F. Girod, C. S. Haley, S. Hassinen, A. Hauchecorne, C. Jiménez, E. Kyrö, N. Lautié, E. Le Flochmoën, N. D. Lloyd, J. C. McConnell, I. C. McDade, L. Nordh, M. Olberg, A. Pazmino, S. V. Petelina, A. Sandqvist, A. Seppälä, C. E. Sioris, et al., Polar vortex evolution during the 2002 Antarctic major warming as observed by the Odin satellite, J. Geophys. Res., 110, D05302, doi:10.1029/2004JD005018, 2005.
19. X. Liu, K. Chance, C. E. Sioris, M. J. Newchurch, T. P. Kurosu, Tropospheric ozone profiles from a ground-based ultraviolet spectrometer: a new retrieval method, Applied Optics, 45(10), 2352-2359, 2006.
20. X. Liu, K. Chance, C. E. Sioris, R. J. D. Spurr, T. P. Kurosu, R. V. Martin, M. J. Newchurch, Ozone profile and tropospheric ozone retrievals from Global Ozone Monitoring Experiment: Algorithm description and validation, J. Geophys. Res., 110, D20307, doi:10.1029/2005JD006240, 2005.
21. C. E. Sioris, L. J. Kovalenko, C. A. McLinden, R. J. Salawitch, M. van Roozendael, F. Goutail, M. Dorf, K. Pfeilsticker, K. Chance, C. von Savigny, X. Liu, T. P. Kurosu, J.-P. Pommereau, H. Bösch, and J. Frerick, Latitudinal and vertical distribution of bromine monoxide in the lower stratosphere from SCIAMACHY limb scattering measurements, J. Geophys. Res., 111, D14301, doi:10.1029/2005JD006479, 2006.
22. G. Lichtenberg, Q. Kleipool, J. M. Krijger, G. van Soest, R. van Hees, L. G. Tilstra, J. R. Acarreta, I. Aben, B. Ahlers, H. Bovensmann, K. Chance, A. M. S. Gloudemans, R. W. M. Hoogeveen, R. Jongma, S. Noël, A. Piters, H. Schrijver, C. Schrijvers, C. E. Sioris, J. Skupin, S. Slijkhuis, P. Stammes, M. Wuttke, SCIAMACHY Level1 data: Calibration concept and in-flight calibration, Atmos. Chem. Phys., 6, 5347-5367, 2006.
23. A. Butz, H. Bösch, C. Camy-Peyret, M. Chipperfield, M.Dorf, G. Dufour, K. Grunow, P. Jeseck, S. Kühl, S. Payan, I. Pepin, J,. Pukite, A. Rozanov, C. von Savigny, C. Sioris, T. Wagner, F. Weidner, K. Pfeilsticker, Inter-comparison of stratospheric O3 and NO2 abundances retrieved from balloon borne direct sun observations and Envisat/SCIAMACHY limb measurements, Atmos. Chem. Phys., 6, 1293-1314, 2006.
24. M. Dorf, H. Bösch, A. Butz, C. Camy-Peyret, M. P. Chipperfield, A. Engel, F. Goutail, K. Grunow, F. Hendrick, S. Hrechanyy, B. Naujokat, J.-P. Pommereau, M. Van Roozendael, C. Sioris, F. Stroh, F. Weidner, and K. Pfeilsticker, Balloon-borne stratospheric BrO measurements: Comparison with Envisat/SCIAMACHY BrO limb profiles, Atmos. Chem. Phys., 6, 2483-2501, 2006.
25. X. Liu, K. Chance, C. E. Sioris, T. P. Kurosu, R. J. D. Spurr, R. V. Martin, T.-M. Fu, J. A. Logan, D. J. Jacob, P. I. Palmer, M. J. Newchurch, I. A. Megretskaia, and R. B. Chatfield, First directly retrieved global distribution of tropospheric column ozone from GOME: Comparison with the GEOS-CHEM model, J. Geophys. Res., 111, D02308, 10.1029/2005JD006564, 2006.
26. C. A. McLinden, C. S. Haley, and C. E. Sioris, Diurnal effects in limb scattering observations, J. Geophys. Res., 111, D14302, doi:10.1029/2005JD006628, 2006.
27. X. Liu, K. Chance, C. E. Sioris, T. P. Kurosu, and M. J. Newchurch, Intercomparison of GOME, ozonesonde, and SAGE-II measurements of ozone: Demonstration of the need to homogenize available ozonesonde datasets, J. Geophys. Res., 111, D14305, doi:10.1029/2005JD006718, 2006.
28. R. V. Martin, C. E. Sioris, K. Chance, T. B. Ryerson, T. H. Bertram, P. J. Wooldridge, R. C. Cohen, J. A. Neuman, A. Swanson, and F. M. Flocke, Evaluation of space-based constraints on global nitrogen oxide emissions with regional aircraft measurements over and downwind of eastern North America, J. Geophys. Res., 111, D15308, doi:10.1029/2005JD006680, 2006.
29. X. Liu, K. Chance, C. E. Sioris, and T. P. Kurosu, Impact of using different ozone cross sections on ozone profile retrievals from Global Ozone Monitoring Experiment (GOME) ultraviolet measurements, Atmos. Chem. Phys. , 7, 3571–3578, 2007.
30. R. V. Martin, B. Sauvage, I. Folkins, C. E. Sioris, C. Boone, P. Bernath, and J. Ziemke, Space-based constraints on the production of nitric oxide by lightning, J. Geophys. Res., 112, D09309, doi:10.1029/2006JD007831, 2007.
31. S. M. Brohede, C. S. Haley, C. A. McLinden, C. E. Sioris, D. P. Murtagh, S. V. Petelina, E. J. Llewellyn, A. Bazureau, F. Goutail, C. E. Randall, J. D. Lumpe, G. Taha, L. W. Thomason, L. L. Gordley, Validation of Odin/OSIRIS stratospheric NO2 profiles, J. Geophys. Res., 112, D07310, doi:10.1029/2006JD007586, 2007.
32. S. M. Brohede, C. A. McLinden, G. Berthet, C. S. Haley, D. Murtagh, and C. E. Sioris, A Stratospheric NO2 climatology from Odin/OSIRIS limb-scatter measurements, Can J. Phys., 85, 1253-1274, 2007.
33. C. E. Sioris, S. Chabrillat, C. A. McLinden, C. S. Haley, R. Ménard, M. Charron, and C. T. McElroy, OSIRIS observations of a tongue of NOx in the lower stratosphere at the Antarctic vortex edge: comparison with a high resolution simulation from the Global Environmental Multiscale (GEM) model, Can. J. Phys., 85, 1195-1207, 2007. pdf
34. C. E. Sioris, C. A. McLinden, R. V. Martin, B. Sauvage, C. S. Haley, N. D. Lloyd, E. J. Llewellyn, P. F. Bernath, C. D. Boone, S. Brohede, and C. T. McElroy, Vertical profiles of lightning-produced NO2 enhancements in the upper troposphere observed by OSIRIS, Atmos. Chem. Phys., 7, 4281-4294, 2007.
35. M. R. Carleer, C. D. Boone, K. A. Walker, P. F. Bernath, K. Strong, R. J. Sica, C. E. Randall, H. Vömel, J. Kar, M. Höpfner, M. Milz, T. von Clarmann, R. Kivi, J. Valverde-Canossa, C. E. Sioris, M. R. M. Izawa, E. Dupuy, C. T. McElroy, J. R. Drummond, C. R. Nowlan, J. Zou, F. Nichitiu, S. Lossow, J. Urban, D. Murtagh, and D. G. Dufour, Validation of water vapour profiles from the Atmospheric Chemistry Experiment (ACE), Atmos. Chem. Phys. Discuss., 8, 4499–4559, 2008.
36. B. Kaynak, Y. Hu, R. V. Martin, A. G. Russell, and C. E. Sioris, Comparison of weekly cycle of NO2 satellite retrievals and NOx emission inventories for the continental U.S., J. Geophys. Res., accepted.
37. G. Liu, D. W. Tarasick, V. E. Fioletov, C. E. Sioris, and Y. J. Rochon, Ozone correlation lengths and measurement uncertainties from analysis of historical ozonesonde data in North America and Europe, J. Geophys. Res., 114, D04112, doi:10.1029/2008JD010576, 2009.
see also: K. Chance, Ultraviolet and visible spectroscopy and spaceborne remote sensing of the Earth's atmosphere, C. R. Physique, 6,836-847, 2005.
AGU Poster
Sioris, C. E., C. von Savigny, R. L. Gattinger, J. C. McConnell, I. C. McDade, E. Griffioen, E. J. Llewellyn, and the ODIN team, Attitude determination for limb-scanning satellites: The "knee" at 305 nm, Eos Trans. AGU, 82(47), Fall Meet. Suppl., Abstract A32B-0056, 2001.
Non-refereed publications
1. Smorenburg, K., G. B. Courrèges-Lacoste, M. Berger, C. Buschmann, A. Court, U. Del Bello, G. Langsdorf, H. K. Lichtenthaler, C. Sioris, M.-P. Stoll, H. Visser, Remote sensing of solar induced fluorescence of vegetation, Proc. SPIE, 4542, 178-190, 2002.
Please send any comments to me at csioris@cfa.harvard.edu
.
The line strengths of O2 have been recalculated. Two errors were found in the best existing line strength data (Altmann et al., 1972) and do not result from their use of less precise eigenvectors. For the first two QP-branch Stokes transitions (1,2->1,1) and (3,4->3,3), I obtain 0.6925 and 0.3592 whereas they calculated 0.55 and 0.34. The line strength is simply the Placzek-Teller coefficient multiplied by the initial state degeneracy.
Reference:
Altmann, K., G. Strey, J. G. Hochenbleicher, and J. Brandmüller, Simulation des Intensitätsverlaufs im Raman-spektrum von Sauerstoff unter Berücksichtigung der Spinaufspaltung, Z. Naturforsch. A27, 56-64, 1972.
Here is the poster I presented at the Gordon Research Conference on Solar Radiation and Climate:
Raman scattering in the O2 A band
The Ring effect is the filling in of absorption lines caused almost entirely by rotational Raman scattering (RRS, see Figure 1).
Figure 1 - Rotational Raman "stick" spectrum of N2 and O2 at 258K for 762 nm (13123 cm-1)excitation
Measurements or modelling of the Ring effect have yet to consider the A band (Figure 2).
Figure 2 - A band measured at Mirabel, Que. under cloudy skies with 0.5 cm-1 (30 pm) resolution Fourier transform spectrometer
The filling in spectrum is given by F= R/Ic where R is the net Raman scattered radiance and Ic is the continuum radiance.
Method
The net Raman scattered radiance is given by:
where
T : path transmission
PRam: Raman scattering phase function
DsRam: net Raman scattering cross section (= sin -sout)
n: number density
Mie scattering (vis=50km) is included in RT calculations
Observations and Discussion
Rotational Raman scattering fills in A band lines modelled from nadir- viewing satellite geometry (Figure 3) by 2% in some of the P-branch lines.
Figure 3 - Filling in of the A band at 2 cm-1 resolution from satellite looking down at clear sky, SZA=90°.
Lower values are expected for cloudy scenes, heavier aerosol loadings and for high sun.
The filling in of the A band lines is negligible in zenith-sky spectra from the ground (Figure 4) even in a worst case scenario as the absolute difference in radiance in the A band lines due to the inclusion of RRS is very small.
Figure 4 - Filling in spectrum at 2 cm-1 (0.12 nm) resolution for clear zenith-sky from ground, SZA=90°.
However, the shape of the pressure-broadened R branch wing is modified
Results for limb viewing geometry and various clear and overcast nadir scenarios are discussed in my recent GRL paper (browse GRL Dec. 15th, 2000).
Modelling degree of LP in the near UV
I am also working on including multiple scattering and polarization in my Ring effect code in the UV-vis. I have simulated the polarimetric zenith sky observations of Aben et al.(GRL 26:591) with incredible precision (1%) in the 350-400 nm region for SZA=79°. This was only possible thanks to their detailed description of environmental conditions.
The method used will not work as well at much shorter wavelengths because of strong absorption by the Huggins band of ozone. At longer wavelengths, multiple Mie scattering, which is not properly included here, becomes important relative to Rayleigh scattering and again the method will likely fail. The same is true for the observations made at higher solar zenith angles (66 and 58°) where degree of LP errors reach 2.5 and 5% at worst, respectively. This approach also works well for dark surfaces.
This method is extremely fast computationally (~30 sec). These are the first polarized RT calculations with line-by-line RRS to my knowledge, although Humphreys, Kattawar and Young should be credited for their RT model in 1984 which treated the RRS in an approximate fashion and recently Aben et al. published results of their model LP spectrum for 2 orders of scattering.
Assumptions
-> two stream approximation
-> Solar spectrum "NewKurucz" from MODTRAN4 smoothed with boxcar to match 0.17 nm resolution of GOME channel 2.
-> Higher order (3rd+) scattering assumed to be isotropic.
Degree of LP is defined:(V-H)/(V+H), where V is the intensity perpendicular (vertical) to the scattering plane and H is the intensity parallel (horizontal) to the scattering plane.
Discussion
Fine structure due exclusively to RRS is almost perfectly simulated. Differences are likely due to the difference in the observed and model solar spectra.
The novel method used here is described in my thesis
(defended April 17, 2001) and in my JQSRT paper (see above).
A pdf version of my thesis will be put on here soon, but for now, hopefully everything comes out OK when you view it with Word.
Last modified March 8th, 2008.