Airborne Sunphotometry in Support of the Airborne Sunphotometry in Support of the Chesapeake Lighthouse and Aircraft Measurements Chesapeake Lighthouse and Aircraft Measurements

for Satellites (CLAMS) Experiment, 2001for Satellites (CLAMS) Experiment, 2001

Jens RedemannJens Redemann11, B. Schmid, B. Schmid11, J. M. Livingston, J. M. Livingston22, P. B. Russell, P. B. Russell33, J. E. Eilers, J. E. Eilers33, , P. V. HobbsP. V. Hobbs44, R. Kahn, R. Kahn55, W. L. Smith Jr., W. L. Smith Jr.66,, B. HolbenB. Holben7 7 , K. Rutledge, K. Rutledge88

11Bay Area Environmental Research Institute, CABay Area Environmental Research Institute, CA22SRI International, CA, SRI International, CA, 33NASA Ames Research Center, CA NASA Ames Research Center, CA 44University of Washington, WA, University of Washington, WA, 55Jet Propulsion Lab, CAJet Propulsion Lab, CA

66NASA LaRC, VA, NASA LaRC, VA, 77NASA GSFC, MD, NASA GSFC, MD, 88AS&M, Inc./NASA LaRC, VAAS&M, Inc./NASA LaRC, VA

ContentsContents1.1. Purpose of CLAMSPurpose of CLAMS2.2. Sunphotometer measurements aboard the Sunphotometer measurements aboard the

UW CV-580 – comparability with other UW CV-580 – comparability with other platforms and instrumentsplatforms and instruments

3.3. Comparisons of AATS-14 to AERONET Cimel Comparisons of AATS-14 to AERONET Cimel sunphotometer at COVEsunphotometer at COVE

4.4. First validation attempts of the MISR First validation attempts of the MISR standard algorithmstandard algorithm

5.5. Spatial statistics of AOD off the US East Spatial statistics of AOD off the US East CoastCoast

6.6. ConclusionsConclusions

Chesapeake Lighthouse: Centerpiece of CLAMS observationsChesapeake Lighthouse: Centerpiece of CLAMS observations

• CLAMS: clear sky, shortwave (SW) closure campaign

• CERES, MISR, MODIS-Atmospheres, and the NASA/GEWEX/GACP

• Measurements from:A. Chesapeake Lighthouse research

platform (36.9N,75.7W), B. 6 research aircraft,C. TERRA satellite • CLAMS research goals: A. validation of satellite-based

retrievals of aerosol properties, B. vertical profiles of radiative

fluxes, C. temperature and water vapor

AATS-14 aboard the UW CV-580AATS-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 (ozone) + water vapor (ozone) 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

Typical Typical UW CV-580 UW CV-580 flight track in flight track in

CLAMSCLAMS

Chesapeake Lighthouse

Typical AATS-14 measurement dayTypical AATS-14 measurement day

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

Statistics of AERONET vs. AATS-14 at COVE, July 10 – Aug.2, 2001Statistics of AERONET vs. AATS-14 at COVE, July 10 – Aug.2, 2001

y=1.035x+0.016r2=0.995rmse=0.04

y=1.041x+0.002r2=0.993rmse=0.021

y=0.987x-0.004r2=0.959rmse=0.011

y=0.957x-0.005r2=0.916rmse=0.012

CV-580/AATS-14 location, CLAMS July 17, 2001, CV-580/AATS-14 location, CLAMS July 17, 2001, 16:00 - 16:15 UTC16:00 - 16:15 UTC

AOD variability on July 17AOD variability on July 17thth, 2001, 2001

ΔAOD~25%

Comparison between AATS-14, AERONET and MISR (unvalidated Comparison between AATS-14, AERONET and MISR (unvalidated standard algorithm), CLAMS, July 17, 2001standard algorithm), CLAMS, July 17, 2001

Vertical aerosol structure, July 17, 2001Vertical aerosol structure, July 17, 2001

ConclusionsConclusions1. 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.

2. 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 (~0.48 at 499nm), including a horizontal gradient in AOD of more than 0.1 over a horizontal distance of ~80 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 strongest correlation coefficients at 380 and 500 nm).

5. Initial validation studies of the standard MISR AOD algorithm seem to indicate the lack of small particles in the mixture models.

AcknowledgmentAcknowledgment

We gratefully acknowledge funding for We gratefully acknowledge funding for AATS-14 participation in CLAMS through AATS-14 participation in CLAMS through the EOS Validation Program (M. King).the EOS Validation Program (M. King).