1. Trace gas and AOD retrievals from a newly deployed hyper-spectral airborne sun/sky photometer (4STAR) M. Segal-Rosenheimer, C.J. Flynn, J. Redemann, B. Schmid, Y. Shinozuka,S. Dunagan, R.R. Johnson, J.M. Livingston, P.B. Russell

2. 4STAR (Spectrometers for Sky-Scanning, Sun-Tracking Atmospheric Research) is a collaborative development by NASA Ames, PNNL, and NASA Goddard Instrument Features – AATS-like sun tracking Aerosol Optical Depth (AOD) at 13 wavelengths H 2 O vapor column Airborne - Horizontally and vertically resolved – AERONET-like direct beam+ sky scanning AOD Size distributions (mode-resolved) Single-scattering albedo (SSA) Asymmetry parameter Sphericity – Hyperspectrally resolved (>1,000 channels) Two spectrometers (UV-Vis-NIR and SWIR) 4STAR - Introduction 4STAR Head on DOE G-1 Figure: Internal scheme of the instrument. Fiber optic & electrical cable to spectrometers & controls in cabin

3. Direct Sun Mode – AOD/Trace gases Direct Sun Mode – Cirrus Optical Depth/D eff (Segal-Rosenheimer et al., in preparation) Sky Radiance Mode – Size Distributions, SSA (Kassianov et al. submitted) Zenith Mode – Cloud Optical Depth (w upwelling flux) 4STAR – Data Products

4. Direct Sun Mode – AOD/Trace gases Direct Sun Mode – Cirrus Optical Depth/D eff (Segal-Rosenheimer et al., in preparation) Sky Radiance Mode – Size Distributions, SSA (Kassianov et al. submitted) Zenith Mode – Cloud Optical Depth (w upwelling flux)

5. Analysis Methods Airborne Langley Calibration Langley Flight: July 22 nd - Off-coast Cape-Cod

6. Gas Retrievals Water Vapor (H 2 O) Instrument Calibrated TOA spectrum (SCHMID ET AL. 1996)

7. Gas Retrievals Classic Direct Sun DOAS Method (e.g. Herman et al., 2009) MLR (Multiple Linear Regression) Relative spectrumTOA Langley spectrum Spectral range (400-440 nm)Spectral range (440-625 nm) High Order Polynomial (Rayleigh and Aerosols)Accurate Rayleigh Subtraction (Fit Aerosols with 2 nd order Polynomial) Shift and Stretch fit during retrievalShift and Stretch fit before retrieval Non-Linear Least SquaresLinear Least Squares Retrieved gases: NO 2, O 3, O 2 -O 2, H 2 OH 2 O from 940 region  NO 2, O 3, O 2 -O 2 NO 2 /O 3 Swap-in new spectrometer just before the campaign – still not well characterized!

8. Results TCAP (Two Column Aerosol Project Campaign) Airborne (DOE G-1, NASA LaRC King Air) Surface (DOE AMF-1, MAOS) July 7-29, 2012 Cape Cod, MA AMF Ground Site Two column location Hyannis Airport

9. Water Vapor (H 2 O) Flight: July 21 st - Off-coast Cape-Cod Relative SD = 2%

10. Sample spectra (July 21 st 2012) Residual Weak water vapor lines Better characterization of spectrometer FWHM is still needed (not constant).

11. Example steps subtraction (July 21 st 2012) Residual Weak water vapor lines

12. July 21 st G-1 Flight path Hyannis Airport AMF Ground Site Ocean spirals [UT Time]

13. G-1 track and OMI overpass (July 21 st ) Ozone levels RMS difference = 33 [DU] OMI Overpass : 16:20 UT

14. G-1 track and OMI overpass (July 22 nd ) NO 2 levels RMS difference= 4x10 15 [molec cm -2 ] = 0.15 DU OMI Overpass : 17:03 UT

15. Summary: O 3 /NO 2

16. Sample AOD values (July 15 th and 21 st ) Scattered clouds

17. Summary and Future Work Preliminary science products:  H 2 O, O 3, NO 2  AOD Gas retrievals should and can be improved by:  Better instrument slit function characterization  Combination of lamp and Langley calibration Additional validation and comparison work is planned:  DOAS group (Ground ARM site) – NO 2 profiles  Better characterization of ozone profile, H 2 O from radiosonds 4STAR showed full operational capability in its first science campaign:  Sun tracking  Both spectrometers (UV-Vis-NIR + SWIR) collecting data  Zenith viewing  Sky Scanning

18. THANK YOU! Major funding from: -NASA Radiation Science Program -Battelle PNW Division -Department of Energy and ARM -NASA Post-Doctoral Program -Weizmann Institute of Science