1. Jens Redemann 1, B. Schmid 1, J. M. Livingston 2, P. B. Russell 3, J. A. Eilers 3, P. V. Hobbs 4, R. Kahn 5, W. L. Smith Jr. 6, B. N. Holben 7, C.K. Rutledge 8, M.C. Pitts 6, M.I. Mishchenko 9, B. Cairns 10, J. Chowdhary 10, J.V. Martins 11, A. Plana-Fattori 11, R.C. Levy 7, T.P. Charlock 6 1 Bay Area Environmental Research Institute, CA 2 SRI International, CA, 3 NASA Ames Research Center, CA 4 University of Washington, WA, 5 Jet Propulsion Lab, CA 6 NASA LaRC, VA, 7 NASA GSFC, MD, 8 AS&M, Inc./NASA LaRC, VA, 9 NASA GISS, NY, 10 Columbia University, NY, 11 UMBC / NASA GSFC, MD; on leave from the University of Sao Paulo, Brazil Airborne measurements of aerosol optical depth and columnar water vapor in support of the Chesapeake Lighthouse and Aircraft Measurements for Satellites (CLAMS) Experiment, 2001

2. Contents 1.AATS-14 aboard the UW CV-580 2.Comparability with other platforms and instruments 3.Comparisons of AATS-14 to AERONET Cimel sunphotometer at COVE: implications for satellite validation 4.Spatial statistics of AOD off the US East Coast 5.MODIS validation over the ocean 6.Summary

3. AATS-14 aboard the UW CV-580 1.Measures direct solar beam transmission @: 353.5 380.0 449.0 499.4 525.0 605.7 675.1 778.4 864.5 939.7 1019.1 1059.4 1241.3 1557.8 nm 2.Yields: aerosol optical depth + aerosol extinction when A/C flies profiles columnar water vapor + water vapor concentration when A/C flies profiles 3.Size: Telescope dome 8" OD (hemisphere) atop 5" H pedestal. (Total H: 9" above A/C skin), Inside A/C: 12" D x 18" H cylinder. 4.Weight: 131.6 lbs

4. Typical UW CV-580 flight track in CLAMS Chesapeake Lighthouse

5. Typical AATS-14 measurement day

6. AERONET vs. AATS-14 at COVE, July 17, 2001

7. Statistics of AERONET vs. AATS-14 at COVE, July 10 – Aug.2, 2001 y=1.035x+0.016 r 2 =0.995 rmse=0.04 y=1.041x+0.002 r 2 =0.993 rmse=0.021 y=0.987x- 0.004 r 2 =0.959 rmse=0.011 y=0.957x- 0.005 r 2 =0.916 rmse=0.012

8. Suborbital measurements of AOD - spatial vs. temporal variability: Temporal:Long-termTemporal:Short-term Spatial resolution Ground-based (e.g., AERONET) yes yes (15 min.) nono Ship-based sunphotometer yesyesno?? Aircraft-based TDDR nopossibleyes 45 sec. ~ 3-4 km Aircraft-basedAATSnopossibleyes 2 sec. ~ 100-200 m

9. CV-580/AATS-14 location, CLAMS July 17, 2001, 16:00 - 16:15 UTC

10. AOD variability on July 17 th, 2001 Δ AOD~30%

11. AATS-14 vs. AERONET: spatial and temporal variability

12. AATS-14: spatial variability

13. Summary of AATS-14 derived AOD spatial variability by flight in CLAMS-2001

15. MODIS: 6 wavelengths validation over ocean CLAMS AOD Validation Courtesy of R. Levy, MODIS team

16. Vertical aerosol structure, July 17, 2001

17. Vertical water vapor structure, July 17, 2001

18. Summary 1.Available as of Feb. 23, 2002: Version 1.0 of all full-column measurements of AATS-14 in CLAMS in 11 ASCII data files (one per CV-580 flight). 2.In CLAMS, AATS-14 measured full column aerosol optical depth spectra and columnar water vapor at exact TERRA overpass time on at least 7 occasions. For five of these opportunities, AOD at 499nm was at or below 0.1. 3.During TERRA overpass time on July 17, 2001, AATS-14 measured the highest AOD encountered during the entire experiment (~0.49 at 499nm), including a horizontal gradient in AOD of more than 30% over a horizontal distance of ~70 kilometers. 4.Comparisons between airborne AATS-14 in the vicinity of and AERONET Cimel derived AOD’s directly at the Chesapeake Lighthouse show good agreement and complementary results in assessing both spatial and temporal AOD variability. 5.AOD variability during low-level legs of 11 research flights was frequently as high as 50% over distances ≤ 50 km.