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Using Sun and Aureole Measurements to Check MODIS COD and R eff Retrievals for Cirrus

Please open in “Notes” mode to see the notes. Using Sun and Aureole Measurements to Check MODIS COD and R eff Retrievals for Cirrus. Prepared for MODIS/VIIRS Science Team Meeting J.G. DeVore, A.T. Stair, A.J. LePage, D. Villanucci, … Washington, DC January 2010. 1. Introduction.

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Using Sun and Aureole Measurements to Check MODIS COD and R eff Retrievals for Cirrus

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  1. Please open in “Notes” mode to see the notes. Using Sun and Aureole Measurements to Check MODIS COD and Reff Retrievals for Cirrus Prepared for MODIS/VIIRS Science Team Meeting J.G. DeVore, A.T. Stair, A.J. LePage, D. Villanucci, … Washington, DC January 2010

  2. 1. Introduction • Cirrus is important for climate • ~ 25% coverage globally • Climate effects arepoorly understood • In-situ measurement is difficult • Reason for SPARTICUS, MACPEX • Remote measurement is difficult • Complex shapes • Strong forward scattering • Sun and aureole measurements, SAM1 (see notesin section 10) • New validation tool2 • Data will be available during above campaigns

  3. 2. SAM Calibration • SAM radiance measurements • Solar disk and aureole profiles • At 670 +/- 5 nm • Lab calibration NIST traceable • Field OD secondary calibration using AERONET • Integration time and temperature corrected • Radiometric radiance accuracy: • Aureole ~15% • Disk <1% if OD<~0.6, <~10% otherwise • Aureole profile gradient (precision) <0.5%

  4. 3. Example 1: GSFC 11 NOV 08 • MODIS retrievals of COD and Reff are nearly uniform • LOS parallax is accounted for

  5. 4. SAM Disk, Aureole Profiles • SAM aureole profiles are nearly identical • Black curve shows center and inter-measurement spread

  6. 5. Data And MCAP Simulations3 • Simulations using MODIS COD, Reff, and Yang/Baum phase functions don’t match data

  7. 6. Example 2: GSFC 10 FEB 09 • Simulations using MODIS COD, Reff, and Yang/Baum phase functions don’t match data

  8. 7. Example 3: GSFC 10 FEB 09 • When COD is adjusted ad hoc, the simulated aureole is too high

  9. 8. COD Corrections Attempted4 • Delta photons for MODIS • Forward scattering for SAM

  10. 9. Conclusions • SAM is a new Cal/Val technique • Suggest independent verification • Review MODIS phase functions • Perform comparisons with other datasets • Raman lidar, MFRSR, GOES, CALIPSO, SPARTICUS • Develop SAM OD correction for forward scattering • Use aureole measurements • Verify and validate

  11. 10. Acknowledgementsand End Notes 1 SAM is described in a recent paper: J. Atmos. Ocen. Tech., 25, pgs 2531-2548, 2009 The authors acknowledge and thank: Dr. Hal Maring and the NASA Science Mission Directorate for support through a ROSES grant, 2Dr. Bryan Baum and Prof. Ping Yang, who suggested this line of research, 3Dr. Yu You (TAMU), who has performed scattering calculations, showing similar effects on SAM COD measurements, and 4Drs. Steve Platnick and Zhibo Zhang (GSFC), for their help with the MODIS delta photon correction.

  12. Deployed SAM Instruments SAM #300 at DOE/ARM CF (OK) SAM #303 at NASA/GSFC

  13. SAM Applications • Climate (cloud) monitoring • Cloud physics research • Satellite algorithm cal/val • Circumsolar radiation Contacts: Dr. John DeVore 781-791-3209 devore@visidyne.com Dr. A.T. Stair 781-273-2820 ats@visidyne.com

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