Poster Presentation

1
Intercomparison of Ground-based Column Ozone
Measurements with Aura Satellite Retrievals over
Richland, WA during INTEX-B/IONS-06 Wan
Ching Jacquie Hui1, Brett Taubman2, Anne
Thompson1, Mark Schoeberl3, and Eugene
Clothiaux1 1Department of Meteorology,
Pennsylvania State University, University Park,
PA 16802, USA, amt16_at_psu.edu, 2Appalachian State
University, 3NASA/GSFC
INTRODUCTION
RESULTS AND DISCUSSIONS I
RESULTS AND DISCUSSIONS II (Shadowband Radiometer)
Total Ozone Comparison
The Ozone Monitoring Instrument (OMI) on board
the NASA Earth Observing System Aura Satellite
provides the greatest spatially resolved ozone
retrievals on a global scale. While the
space-borne instrument provides good horizontal
spatial coverage, it is relatively insensitive to
tropospheric chemical concentrations and
therefore requires validation from ground-based
observations. The Pennsylvania State University
Department of Meteorology NATIVE (Nittany
Atmospheric Trailer and Integrated Validation
Experiment, http//www.meteo.psu.edu/btaubman/Web
page/native.html) facility is a mobile
atmospheric research facility that was deployed
in Richland, WA (46.2oN, 119.16oW) from April 21,
2006 through May 15, 2006 as part of the INTEX-B
(Intercontinental Chemical Transport Experiment)
campaign. Soundings were part of the IONS-06
(Thompson et al., 2007). During this period,
NATIVE made column and vertical profile ozone
measurements using ozonesondes, a Microtops
ozonometer, and a UV-MFR (Ultraviolet Multifilter
Radiometer). These measurements were compared
with OMI total column ozone (TCO) and
tropospheric ozone residual (TOR).

• Sonde-retrieved total ozone is on average 13 DU
  higher than OMI-retrieved values over Richland
• Shadowband values (SR-JPL06 and SR-BP85) are
  computed with the same sets of V0, (top of the
  atmosphere solar irradiance). The wavelength
  pairs are (310.7, 323.7 nm) and (316.8, 331.7
  nm).

• Intercomparison among various instruments
  indicate they are highly correlated with each
  other. Among those, total OMI and shadowband
  radiometer give the highest correlation of 0.98
• Total column ozone obtained from the shadowband
  radiometer requires an accurate estimate of V0
  and ozone absorption coefficients
• V0 is estimated through Langley analysis on data
  taken on clear days. Reference to AERONET helped
  to eliminate days when there are large aerosol
  changes within the day

Fig 3. The Langley plot of ln(I) (spectral
irradiance) versus air mass in the morning of May
4th 2006 for 310.7nm. ln(I0) can be extrapolated
to zero air mass and yield the irradiance at the
top of the atmosphere. The slope of the line is
the total optical depth for the particular time
period. The quality of the analysis is best on
clear stable days.

• Due to the limited time period in the campaign
  and the weather condition of the sites, we cannot
  obtain a set of V0s that are close to the
  measurements from other instruments
• The wavelength pairs used in the
  double-wavelength formula also affect TCO (not
  shown)
• Optimization of V0s
• Using four sets of O3 absorption coefficients
  (JPL 2006, Brion 1985, Bass Paur 1985, and
  Voigt 2001), we try to minimize the sum of errors
  between sonde and shadowband values.

Fig 1. Comparison of total ozone with OMI,
ozonesonde, Microtops, and shadowband radiometer
(SR) values during the campaign over Richland.
SR-JPL and SR-BP85 are the shadowband radiometer
measurements derived using JPL 2006 and Bass
Paur 1985 ozone absorption coefficients
respectively.
DATA AND METHODS
Table 1. Correlation coefficients of column
ozone retrieved with the different instruments
during the campaign.
Total OMI Sonde total Microtops SR-BP85 SR-JPL06
Total OMI 1.00
Sonde total 0.95 1.00
Microtops 0.90 0.88 1.00
SR-BP85 0.98 0.94 0.90 1.00
SR-JPL06 0.98 0.94 0.90 1.00 1.00

• Instrumentation
• Ozonesondes ozone profiles were taken during
  INTEX and IONS-06 with En-Sci Electrochemical
  Concentration Cell (ECC) Ozonesondes. Total
  column ozone is calculated by integrating the
  profiles up to a pressure level of 7mb (35km)
  and adding climatological ozone from satellite
  SBUV (solar backscattered UV) above 7mb.
• The UVMFR-7 Shadowband radiometer measures
  atmospheric ozone content based on the absorption
  efficiencies at an 2-nm FWHM centered on 300,
  305.5, 311.5, 317.5, 325, 332.5, and 368 nm. To
  obtain total column ozone, a double-wavelength
  radiative transfer formula is used (Gao et. al.,
  2001).
• Microtops II Ozonometer borrowed from G. Labow
  of NASA/GSFC. It uses five UV channels to
  measure total column ozone. The instrument
  outputs column ozone and aerosol optical depths.
  
• OMI Total column ozone is based on the TOMS v8
  algorithms. Also onboard the Aura, the Microwave
  Limb Sounder (MLS), measures stratospheric ozone
  with high vertical resolution.
• TOR derived by subtracting the MLS SCO
  (stratospheric column ozone) from the TCO,
  according to Schoeberl et al., 2007. Sonde
  estimate of TOR is obtained from integrating the
  O3 profile from surface to the tropopause height.
  

FUTURE WORK
TOR Comparison

• Average absolute difference in TOR 11.8 DU
• Average error (absolute) 32.7 ?
  difference/sonde TOR on a specific day
• Average underestimate by OMI TOR relative to
  sonde 11.6 DU (31 error, 19 out of 24 cases)
• Average overestimate by OMI TOR relative to
  sonde 12.6 DU (39 error, 5 out of 24 cases)
• Apr 27-29 has relatively low ozone mixing ratio
  but high overestimates of OMI TOR, yet good
  estimates in total column ozone

• Continuing optimization on V0 for the
  shandowband radiometer
• Case studies will be used to investigate
  discrepancies among the measurements of OMI (TCO
  and TOR), shadowband radiometer, and ozonesonde
• Extend current study to other IONS data. (e.g.
  WAVES at Beltsville)
• Longer time period in future campaigns would be
  needed for better comparisons and validation of
  satellite retrievals

• References
• Bhartia, P. K. (2002), OMI Algorithm Theoretical
  Basis Document, Vol II, OMI Ozone Products,
  ATBD-MI-02, Version 2.0. NASA Goddard Space
  Flight Center, Greenbelt, MD, USA.
• Gao, W. J., J. R. Slusser, J. H. Gibson, G.
  Scott, D. S. Bigelow, J. Kerr, and B. McArthur
  (2001), Direct-Sun column ozone retrieval by the
  Ultraviolet Multi-filter Rotating Shadow-band
  Radiometer and comparison with those from Brewer
  and Dobson spectrophotometers, Appl. Opt. 40(19),
  31493155
• Thompson A. M., et al. (2007), Intercontinental
  Chemical Transport Experiment Ozonesonde Network
  Study (IONS) 2004 1. Summertime upper
  troposphere/lower stratosphere ozone over
  northeastern North America, J. Geophys. Res.,
  112, D12S12, doi10.1029/2006JD007441.
• M. R. Schoeberl, J. R. Ziemke, B. Bojkov, N.
  Livesey, B. Duncan, S. Strahan, L.  Froidevaux,
  S. Kulawik, P. K. Bhartia, S. Chandra, P. Levelt,
  J. C. Witte, A. M. Thompson, A Trajectory Based
  Estimate of the Tropospheric Column Ozone Column
  Using the Residual Method, J. Geophys. Res.,
  doi10.1029/2007JD008873, in press, 2007.

Fig 2. Comparison of differences in total ozone,
TOR, and SCO between OMI and ozonesonde values.