vi-5474(notesmodisviirsstm10) 1 using sun and aureole measurements to check modis cod and r eff...
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VI-5474(NotesModisViirsStm10) 1
Using Sun and Aureole Measurements to CheckMODIS 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, DCJanuary 2010
Please open in “Notes” mode to see the notes.
VI-5474(NotesModisViirsStm10) 2
1. Introduction
• Cirrus is important for climate
- ~ 25% coverage globally
• Climate effects are poorly 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 notes in section
10)
- New validation tool2
- Data will be available during above campaigns
VI-5474(NotesModisViirsStm10) 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%
VI-5474(NotesModisViirsStm10) 4
3. Example 1: GSFC 11 NOV 08
MODI S AquaCODGSFC 11 NOV 08 ~ 19:10 UT
16 -
14 -
12 -
10 -
8 -
6 -
4 -
2 -
0 -
COD
SAM LOS At Cloud Altitude
MODI S AquaCODGSFC 11 NOV 08 ~ 19:10 UT
16 -
14 -
12 -
10 -
8 -
6 -
4 -
2 -
0 -
COD16 -
14 -
12 -
10 -
8 -
6 -
4 -
2 -
0 -
COD
SAM LOS At Cloud Altitude
• MODIS retrievals of COD and Reff are nearly uniform
• LOS parallax is accounted for
VI-5474(NotesModisViirsStm10) 5
4. SAM Disk, Aureole Profiles
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0.01 0.1 1 10
Angle From Sun Center (Deg)
Radia
nce
(W
/cm2
/sr/
mic
ron)
19.1367 UT 19.1508 UT
19.1650 UT 19.1742 UT19.1833 UT 19.1925 UT
19.2036 UT 19.2128 UT19.2222 UT 19.2314 UT
19.2497 UT Center
SAM #303 - GSFC
11 NOV 2008 ~ 19:10 UT
Solar Elev = 24.6 deg
Measurement Gap
(at low COD)
• SAM aureole profiles are nearly identical• Black curve shows center and inter-measurement spread
VI-5474(NotesModisViirsStm10) 6
5. Data And MCAP Simulations3
• Simulations using MODIS COD, Reff, and Yang/Baum phase functions don’t match data
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0.01 0.1 1 10
Angle From Sun Center (deg)
Radia
nce
(W
/cm2
/sr/
um
)
SAM Radiance Measurement
MODI S Sim (OD=2.25, De=40 um)
MODI S Sim (OD=2.00, De=40 um)
MODI S Sim (OD=2.25, De=50 um)
MODI S Sim (OD=2.00, De=50 um)
SAM #303 - GSFC
11 NOV 2008 ~ 19:10 UT
Solar Elev = 24.6 deg
MODI S Simulation
VI-5474(NotesModisViirsStm10) 7
6. Example 2: GSFC 10 FEB 09
• Simulations using MODIS COD, Reff, and Yang/Baum phase functions don’t match data
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
0.01 0.1 1 10
Angle From Sun Center (deg)
Rad
ian
ce (
W/c
m2/s
r/u
m)
SAM Radiance Measurement
MODI S Sim (OD=4.5, De=40 um)
MODI S Sim (OD=3.5, De=40 um)
MODI S Sim (OD=4.5, De=50 um)
MODI S Sim (OD=3.5, De=50 um)
SAM #303 - GSFC
10 FEB 2009 ~ 15:30 UT
Solar Elev = 31.2 deg
MODI S Simulation
VI-5474(NotesModisViirsStm10) 8
7. Example 3: GSFC 10 FEB 09
1.E-02
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
0.01 0.1 1 10
Angle From Sun Center (deg)
Radia
nce
(W
/cm2
/sr/
um
)
SAM Radiance MeasurementMODI S Sim (OD=4.5, De=50 um)MODI S Sim (OD=3.5, De=50 um)MODI S Sim (OD=4.5, De=60 um)MODI S Sim (OD=3.5, De=60 um)Disk Fit (OD=3.0, De=60 um)Disk Fit (OD=2.5, De=60 um)Disk Fit (OD=3.0, De=70 um)Disk Fit (OD=2.5, De=70 um)
SAM #303 - GSFC
10 FEB 2009 ~ 18:55 UT
Solar Elev = 32.6 deg
MODI S Simulation
Disk Fit
• When COD is adjusted ad hoc, the simulated aureole is too high
VI-5474(NotesModisViirsStm10) 9
8. COD Corrections Attempted4
• Delta photons for MODIS• Forward scattering for SAM
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
-10000 -5000 0 5000 10000Range (m)
Clo
ud O
pti
cal D
epth
0
5
10
15
20
25
30
35
40
45
50Eff
ectiv
e R
adiu
s (micro
n)MODI S OD Delta Cor'd
SAM OD SAM Cor'dMODI S Reff
SAM #303 - GSFC
10 FEB 2009 ~ 18:55
VI-5474(NotesModisViirsStm10) 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
VI-5474(NotesModisViirsStm10) 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, and4Drs. Steve Platnick and Zhibo Zhang (GSFC), for their help with the MODIS delta photon correction.
VI-5474(NotesModisViirsStm10) 12
Deployed SAM Instruments
SAM #303 at NASA/GSFC
SAM #300 at DOE/ARM CF (OK)
VI-5474(NotesModisViirsStm10) 13
SAM Applications
• Climate (cloud) monitoring
• Cloud physics research
• Satellite algorithm cal/val
• Circumsolar radiation
Dr. John DeVore 781-791-3209 devore@visidyne.comDr. A.T. Stair 781-273-2820 ats@visidyne.com
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