# Presentation: 642128

## Retrieval of ozone column content from airborne Sun photometer measurements during SOLVE II: Comparison with coincident satellite and aircraft measurements

**Retrieval of ozone column content from airborne Sun photometer measurements during SOLVE II: Comparison with coincident satellite and aircraft measurements**
- J. Livingston1, B. Schmid2, P. Russell3, J. Eilers3, R. Kolyer3, J. Redemann2, S. Ramirez2, J-H. Yee4, C. Trepte5, L. Thomason5, M. Pitts5,
-  M. Avery5,C. Randall6, J. Lumpe7, R. Bevilacqua8, M. Bittner9, T. Erbertseder9, R. McPeters10, R. Shetter11, J. Kerr12, K. Lamb13
- 1SRI International, Menlo Park, CA USA 2Bay Area Environmental Research Institute, Sonoma, CA USA 3NASA Ames Research Center, Moffett Field, CA USA 4Applied Physics Laboratory, Johns Hopkins University, Laurel, MD USA 5NASA Langley Research Center, Hampton, VA USA 6Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO USA 7Computational Physics, Inc., Springfield, VA USA 8Naval Research Laboratory, Washington, DC USA 9DLR (German Aerospace Center), Oberpfaffenhofen, Wessling, Germany 10NASA Goddard Space Flight Center, Greenbelt, MD USA 11National Center for Atmospheric Research, Boulder, CO USA 12Environment Canada, Cobble Hill, BC Canada 13International Ozone Services, Inc., Toronto, ON Canada

**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 weighted 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.  We also compare AATS-14 ozone retrievals during selected DC-8 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 during the aircraft vertical profile at the start or end of each flight.  We also compare AATS-14 ozone retrievals with values derived from coincident measurements by two other DC-8 based solar occultation instruments: GAMS (the NASA Langley Gas and Aerosol Monitoring System) and DIAS (the NCAR Direct Beam Solar Irradiance Spectroradiometer). **

**COMPARISONS WITH TOMS and GOME**

**COMPARISONS WITH SAGE III AND POAM III**

_**6 Feb 2003**_

_**19-20 Dec 2002**_

_**21 Jan 2003**_

**24 Jan 2003**

**RETRIEVAL METHODOLOGY**

**COMPARISON WITH IN-SITU DATA DURING DC-8 DESCENT ON 6 FEB 2003**

**REFERENCE**

**ABSTRACT**

**MAUNA LOA CALIBRATION COMPARISONS**

- King, M. D., and D. M. Byrne, A method for inferring total ozone content from the spectral variation of total optical depth obtained with a solar radiometer, *J. Atmos. Sci., 33*, 2242-2251, 1976.

- AATS-14 retrievals are shown for the DC-8 southbound and northbound flight segments before (blue – southbound, black – northbound) and after (yellow for both directions) adding an estimate of the amount of ozone below aircraft altitude.  DIAS ozone retrievals (green) obtained during the northbound transect agree with AATS-14 values to within a few DU except at the northern and southern DIAS data boundaries.  Adjusted AATS-14 values reflect a latitudinal gradient similar to that indicated by corresponding TOMS and GOME total column retrievals interpolated to the DC-8 flight track (southbound – cyan, northbound – gray), but exceed the satellite data, which exhibit significant temporal variation, at most latitudes.

- AATS-14 retrievals are presented for data acquired during the DC-8 return flight from Sweden to California.  Data are shown for the latitudinal transect (blue) from 49°N to 35°N at ~12.4 km altitude and for the final descent (red) from 12.4 km to 1.1 km into Edwards Air Force Base.  The yellow band displays the range of values that results after adding estimates of the amount of ozone below aircraft altitude.  AATS-14 retrievals agree well with corresponding TOMS and GOME measurements (cyan) both in shape and in magnitude.

- AATS-14 columnar ozone retrievals for data acquired during the DC-8 descent into Edwards Air Force Base are compared with coincident measurements from FASTOZ, the NASA Langley in-situ fast response ozone sensor on board the DC-8.  FASTOZ measurements of ozone concentration (b) have been normalized to the AATS-14 columnar ozone at 12.4 km altitude and vertically integrated for comparison to AATS-14 retrievals in (a).  Differentiation of a cubic spline fit to AATS-14 columnar ozone retrievals (a) yields ozone concentrations that are compared to FASTOZ data in (b).  Not suprisingly, the second order AATS-14 product is unable to reproduce the fine structure seen by FASTOZ.
- In (c) and (d), corresponding AATS-14 columnar water vapor retrievals are shown to agree well with coincident DC-8 based water vapor density measurements from the NASA Langley Diode Laser Hygrometer (DLH) and with nearby radiosonde data acquired ~1.5 hr earlier.

- AATS-14 columnar ozone retrievals are shown for an extended longitudinal transect during the 21 Jan 2003 DC-8 flight. Coincident AATS-14 and DIAS measurements agree to within an rms difference of ~4.7% (20 DU). After the AATS-14 retrievals are increased by the amount of ozone estimated to lie in the column below aircraft altitude, values are consistent with corresponding TOMS and GOME total column ozone retrievals.  The rms difference between AATS retrievals and GOME retrievals interpolated to DC-8 locations is ~3.3% (12 DU).

- We apply the method of King and Byrne [1976] to retrieve columnar ozone from AATS-14 spectral optical depth measurements.  This approach assumes that the spectral variation in aerosol optical depth (AOD) can be described by a quadratic fitting function in log-log space.  The amount of ozone is varied until the optimum least squares fit is found between the resultant AOD spectrum and that calculated using the fitting function.

**ATMOSPHERIC ATTENUATION**

- Plots (a) and (b) show the variation in AOD and columnar ozone, respectively, measured by AATS-14 during the 24 Jan 2003 flight.  AATS-14 and GAMS retrievals of ozone number density along the line of sight (LOS) are plotted in (c), and agree to within an rms difference of 4.4%.   In (d) and (e), the spatio-temporal variation in AATS-14 columnar ozone along the DC-8 flight track is shown for data acquired at flight altitudes of 9.9 km (10.6-10.9 UT and 11.8-12.2 UT) and 8.74 km (11.0-11.7 UT), respectively.  Values are consistent with the integrated 10.98 UT SAGE III retrieval (color coded dot).

- AATS-14 columnar ozone retrievals have been compared with temporally and spatially near-coincident SAGE III and POAM III measurements of ozone number density during four satellite solar occultation events each.  The rms difference between AATS-14 retrievals and integrated SAGE III values is 19 DU (6%), and the rms difference between corresponding AATS-14 and POAM III retrievals is 10 DU (3%).

- AATS-14 exoatmospheric detector voltages, Vo, were calculated using the Langley plot technique for sunrise measurements acquired at Mauna Loa Observatory (MLO) before and after SOLVE II.  These plots show the effect of uncertainty in Vo on retrieved ozone by comparing coincident measurements by Dobson and Brewer spectrometers with AATS-14 ozone retrievals that use either the actual Vo values calculated from the Langley analysis for the particular day or the mean Vo values from the November and March calibration data.

- This graph shows the optical thickness (from MODTRAN) due to Rayleigh and aerosol scattering and gas absorption along a horizontal path from 10 km altitude to space for the AATS-14 spectral range.

- GOME composite 12UT

- Edwards AFB

**column O****3**** [DU]**

**(d)**

**(e)**