vi-5474(notesmodisviirsstm10) 1 using sun and aureole measurements to check modis cod and r eff...

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.


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


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%


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


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


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)




SAM #303 - GSFC

11 NOV 2008 ~ 19:10 UT


MODI S Simulation


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


Rad

ian

ce (

W/c

m2/s

r/u

m)

SAM Radiance Measurement





SAM #303 - GSFC

10 FEB 2009 ~ 15:30 UT


MODI S Simulation


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


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


MODI S Simulation

Disk Fit

• When COD is adjusted ad hoc, the simulated aureole is too high


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


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


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.


Deployed SAM Instruments

SAM #303 at NASA/GSFC

SAM #300 at DOE/ARM CF (OK)


SAM Applications

• Climate (cloud) monitoring

• Cloud physics research

• Satellite algorithm cal/val

• Circumsolar radiation

Dr. John DeVore 781-791-3209 [email protected]. A.T. Stair 781-273-2820 [email protected]

Contacts:

vi-5474(notesmodisviirsstm10) 1 using sun and aureole measurements to check modis cod and r eff...

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