The SOLSELORE2 Experiment: Ozone profiles retrieved from limb scattering measurements

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The SOLSE/LORE-2 Experiment Ozone profiles
retrieved from limb scattering measurements
R. Loughman1, R. McPeters3, D. Flittner2, E.
Hilsenrath3, S. Janz3, T. Brown3, D. Rault2, M.
Hill1, S. Petelina4, and C. von Savigny5
1 Center for Atmospheric Science, Hampton
University, Hampton, VA 2 Radiation and Aerosol
Branch, NASA Langley Research Center, Hampton,
VA 3 Atmospheric Chemistry and Dynamics Branch,
NASA Goddard Space Flight Center, Greenbelt,
MD 4 Institute of Space and Atmospheric Studies,
University of Saskatchewan, Saskatoon, SK,
Canada 5 Institute of Environmental Physics and
Remote Sensing, University of Bremen, Bremen,
Germany
3rd International Atmospheric Limb
Workshop Montréal, Canada, April 25, 2006
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Outline

• Relationship to OMPS limb profiler instrument
• Description of SOLSE/LORE instruments and data
• Discussion of key challenges
• Pointing
• Stray light
• Algorithm description
• Comparison of ozone retrievals to correlative
  data
• Conclusions

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Future Applications of Limb Scattering for Ozone
Retrieval
The Ozone Mapper Profiler Suite (OMPS) includes a
limb scattering instrument to provide
stratospheric ozone profile information.
The tri-agency Integrated Program Office (NASA,
NOAA, Dept. of Defense) has committed to limb
scattering to provide ozone profile retrievals,
beginning in 2009. The main purpose of the
SOLSE/LORE-2 and SAGE III limb scattering
research efforts is to test our current knowledge
of instrument design and retrieval algorithms for
this relatively unproven technique.
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SOLSEs Role as an OMPSLimb Profiler Predecessor

• SOLSE was the model for the instrument design of
  the OMPS limb profiler (LP) instrument, and they
  share many key design features (e.g., measuring a
  simultaneous image of all wavelengths and tangent
  heights). SOLSE and LORE were re-flown primarily
  as a risk-reduction measure for OMPS.
• But the SOLSE design differs from the OMPS LP
  design in two key areas
• Indirect derivation of pointing information
  (using LORE data)
• Introduction of neutral density filters to reduce
  stray light

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SOLSE/LOREinstrument characteristics
SOLSE-2 and LORE-2 flew on the Space Shuttle
(STS-107) in January 2003. The instruments were
redesigned (relative to the instruments that flew
on STS-87 in 1997) to focus on O3 retrievals in
the lower stratosphere.
SOLSE-2

• Imaging spectrometer, 533-863 nm, at 0.8 to 1.2
  nm resolution
• A small subset of spectral data (9 groups of 12
  pixels, each covering 3-4
• nm) was downlinked during the mission
• Filter wheel instrument, with observations made
  at 322, 350, 603, 675
• and 1000 nm (slit width 3-4 nm)

LORE-2
Altitude resolution is 1 km at the tangent point
for both instruments. Triplet ozone retrieval
(Flittner et al., 2000) is currently implemented.
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Available data sets

• 1/9 of the SOLSE-2 images and 3/4 of the LORE-2
  images were downlinked during the flight.
• The remaining images were stored only on the
  instrument hard drives and were therefore lost in
  the shuttle tragedy.
• The surviving data set includes 536 LORE and 168
  SOLSE images, taken between Jan. 19 and Jan. 27,
  2003.
• Surviving SOLSE super-pixels are centered at
  555, 585, 603, 612, 643, 675, 688, 719, 755, 761,
  780, and 823 nm

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Tangent Height Registration

• Done by the RSAS method (Janz et al., 1997),
  which uses the shape of the LORE 350 nm radiance
  profile.
• But the LORE 350 nm filter measurement and the
  SOLSE measurement often are not simultaneous (and
  are frequently separated by gt 30 s).
• Shuttle attitude information (PATH data) can be
  used to interpolate the pointing between LORE 350
  nm filter measurements, but
• This interpolation introduces a significant (but
  difficult-to-quantify) error in the SOLSE tangent
  height registration (see next page).
• The relative alignment of the SOLSE and LORE
  instruments apparently changed during the flight.
  Transferring tangent height registration from
  LORE to SOLSE by assuming that the instrument
  boresight alignment remains unchanged would
  introduce additional error. A correction has
  been applied, but the accuracy of the correction
  is uncertain.

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Uncertainty in SOLSE Pointing
Disagreement between PATH-interpolated and
time-interpolated altitude registration is often
gt 1 km, and differences can be as large as 30 km.
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Green line SOLSE data, Black line LORE data,
at 675 nm These two frames are well-synchronized
at 675 nm (to 1 s and 2 s, respectively). Instrum
ent misalignment for observations through the
Jan. 21 frames is nearly negligible (-0.15 0.53
km) after Jan. 21 frames, a noticeable
misalignment appears (2.26 km 0.22 km). A
thermal event that followed the Jan. 21
measurements may be the culprit.
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SOLSE Neutral Density Filters
The influence of the ND filter boundaries extends
over several spatial pixels. Analysis of flight
data also suggests significant stray light whose
spatial and spectral characteristics are not
captured in the laboratory instrument
characterization. Without the entire SOLSE
spectrum, deconvolution is not practical.
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SOLSE Ozone Retrieval Validation Procedure

• Use only the middle range of the ND filter.
• Concentrate on cases for which middle ND filter
  includes 15-35 km tangent heights (62 usable
  frames of data remain).
• From that subset, focus on cases for which the
  SOLSE and LORE 350 nm measurements are
  synchronized to within 1 s (27 usable frames
  remain).
• Retrieval uses GSLS model (Loughman et al.,
  2004).
• Use SAGE II weekly zonal mean aerosol profiles,
  and climatological T, p, and ozone data as a
  priori information.
• Compare retrieved ozone profile to independent
  data sources.

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Description of coincident data

• OSIRIS (V1.2, pointing adjusted by 0.4 km, as
  suggested by Petelina)
• SAGE II (V6.2)
• SAGE III LS
• SCIAMACHY (V1.63)
• SONDE (obtained from the WOUDC archive)
• The following plots show all cases for which ?t
  lt 12 hrs, ?? lt 5?, ?? lt 20?, and ?? lt 20 DU.
• Of the 27 remaining SOLSE frames, 8 have
  correlative data, but 3 were excluded because the
  SOLSE-2 algorithm did not converge satisfactorily
  (sometimes a large apparent pointing error
  appears to exist).

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SOLSE Frame 41 (Jan. 20, Japan)
Comparison to Naha O3 sonde
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SOLSE Frame 84 (Jan. 21, Alabama)
Comparison to Huntsville O3 sondes
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SOLSE Frame 125 (Jan. 24, Cameroon)
Comparison to OSIRIS and SCIAMACHY O3 profiles
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SOLSE Frame 128 (Jan. 27, Sudan)
Comparison to OSIRIS and SCIAMACHY O3 profiles
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SOLSE Frame 130 (Jan. 27, Dubai)
Comparison to OSIRIS, SAGE III LS, and SCIAMACHY
O3 profiles
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Illustration of the SOLSE Frame 130 coincidence
(Jan. 27, 2003)
The SAGE III and SOLSE/ LORE-2 lines of sight are
aligned to within 7? in azimuth, the tangent
points coincide to better than 2? in both
latitude and longitude, and the observation times
are separated by lt 20 min. However, The SAGE III
1017 nm channel observation shows a sharp feature
(cirrus cloud?) at 12 km, while the SOLSE/LORE-2
data shows a similar feature at 5 km. Despite
their close proximity in space and time, this
suggests that the scenes are not identical.
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Conclusions

• Comparison of the SOLSE-2 ozone retrievals with
  correlative data shows generally good results
  (agreement to within 25 with SAGE II, OSIRIS,
  SAGE III LS, and SCIAMACHY, and ozonesonde data,
  allowing for apparent tangent height registration
  differences).
• Stray light characterization and tangent height
  registration of the SOLSE radiance profiles
  remain major challenges.
• Acknowledgements This work was made possible by
  the tireless efforts of the SOLSE/LORE-2
  instrument team, and by the consistent support
  and advocacy provided by the IPO. We thank the
  SAGE II, SAGE III, OSIRIS and SCIAMACHY teams for
  producing high-quality data and making it
  available for comparison. We also greatly
  appreciate the groups that provided ozonesonde
  data, and acknowledge the WOUDC for archiving it.
  Finally, we recognize the supreme sacrifice made
  by the crew of STS-107, and appreciate the
  opportunity to contribute to their legacy through
  analysis of the SOLSE/LORE-2 data.

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BACKUP SLIDES
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SOLSE Validation