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| Titel |
Retrieval of ozone column content from airborne Sun photometer measurements during SOLVE II: comparison with coincident satellite and aircraft measurements |
| VerfasserIn |
J. M. Livingston, B. Schmid, P. B. Russell, J. A. Eilers, R. W. Kolyer, J. Redemann, S. R. Ramirez, J.-H. Yee, W. H. Swartz, C. R. Trepte, L. W. Thomason, M. C. Pitts, M. A. Avery, C. E. Randall, J. D. Lumpe, R. M. Bevilacqua, M. Bittner, T. Erbertseder, R. D. McPeters, R. E. Shetter, E. V. Browell, J. B. Kerr, K. Lamb |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 5, no. 8 ; Nr. 5, no. 8 (2005-08-08), S.2035-2054 |
| Datensatznummer |
250003023
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| Publikation (Nr.) |
 copernicus.org/acp-5-2035-2005.pdf |
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| Zusammenfassung |
| During the 2003 SAGE (Stratospheric Aerosol and Gas Experiment) III Ozone
Loss and Validation Experiment (SOLVE) II, the fourteen-channel NASA Ames
Airborne Tracking Sunphotometer (AATS-14) was mounted on the NASA DC-8
aircraft and measured spectra of total and aerosol optical depth (TOD and
AOD) during the sunlit portions of eight science flights. Values of ozone
column content above the aircraft have been derived from the AATS-14
measurements by using a linear least squares method that exploits the
differential ozone absorption in the seven AATS-14 channels located within
the Chappuis band. We compare AATS-14 columnar ozone retrievals with
temporally and spatially near-coincident measurements acquired by the SAGE
III and the Polar Ozone and Aerosol Measurement (POAM) III satellite sensors
during four solar occultation events observed by each satellite. RMS
differences are 19 DU (7% of the AATS value) for AATS-SAGE and 10 DU
(3% of the AATS value) for AATS-POAM. In these checks of consistency
between AATS-14 and SAGE III or POAM III ozone results, the AATS-14 analyses
use airmass factors derived from the relative vertical profiles of ozone and
aerosol extinction obtained by SAGE III or POAM III.
We also compare AATS-14 ozone retrievals for measurements obtained during
three DC-8 flights that included extended horizontal transects with total
column ozone data acquired by the Total Ozone Mapping Spectrometer (TOMS)
and the Global Ozone Monitoring Experiment (GOME) satellite sensors. To
enable these comparisons, the amount of ozone in the column below the
aircraft is estimated either by assuming a climatological model or by
combining SAGE and/or POAM data with high resolution in-situ ozone
measurements acquired by the NASA Langley Research Center chemiluminescent
ozone sensor, FASTOZ, during the aircraft vertical profile at the start or
end of each flight. Resultant total column ozone values agree with
corresponding TOMS and GOME measurements to within 10-15 DU (~3%)
for AATS data acquired during two flights - a longitudinal transect from
Sweden to Greenland on 21 January, and a latitudinal transect from 47° N
to 35° N on 6 February. For the round trip DC-8 latitudinal transect
between 34° N and 22° N on 19-20 December 2002, resultant AATS-14
ozone retrievals plus below-aircraft ozone estimates yield a latitudinal
gradient that is similar in shape to that observed by TOMS and GOME, but
resultant AATS values exceed the corresponding satellite values by up to 30 DU
at certain latitudes. These differences are unexplained, but they are
attributed to spatial and temporal variability that was associated with the
dynamics near the subtropical jet but was unresolved by the satellite
sensors.
For selected cases, we also compare AATS-14 ozone retrievals with values
derived from coincident measurements by the other two DC-8 based solar
occultation instruments: the National Center for Atmospheric Research Direct
beam Irradiance Airborne Spectrometer (DIAS) and the NASA Langley Research
Center Gas and Aerosol Monitoring System (GAMS). AATS and DIAS retrievals
agree to within RMS differences of 1% of the AATS values for the 21
January and 19-20 December flights, and 2.3% for the 6 February flight.
Corresponding AATS-GAMS RMS differences are ~1.5% for the 21
January flight; GAMS data were not compared for the 6 February flight and
were not available for the 19-20 December flight. Line of sight ozone
retrievals from coincident measurements obtained by the three DC-8 solar
occultation instruments during the SAGE III solar occultation event on 24
January yield RMS differences of 2.1% for AATS-DIAS and 0.5% for
AATS-GAMS. |
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