Detector dependency of MODIS Polarization Sensitivity derived from on-orbit characterization

Post on 12-Jan-2016

29 views 0 download

description

Detector dependency of MODIS Polarization Sensitivity derived from on-orbit characterization. Gerhard Meister a,b , Bryan A. Franz b,c , Ewa J. Kwiatkoska d , Robert E. Eplee e,b , Charles R. McClain b,c a: Futuretech Corp. b: OBPG (Ocean Biology Processing Group) - PowerPoint PPT Presentation

Transcript of Detector dependency of MODIS Polarization Sensitivity derived from on-orbit characterization

2

4

Detector dependency of MODIS Polarization Sensitivity derived from on-orbit

characterization

Gerhard Meistera,b, Bryan A. Franzb,c, Ewa J. Kwiatkoskad, Robert E. Epleee,b, Charles R. McClainb,c

a: Futuretech Corp. b: OBPG (Ocean Biology Processing Group)

c: NASA Goddard Space Flight Center, Code 614.2d: TEC-EEP, ESTEC, ESA

e: SAIC

8/03/09

Earth Observing Systems XIV,

SPIE Optics and Photonics 2009, San Diego

5

Optimization process

Lm = M11LTOA + M12Q + M13U

• find best M11

, M12

, M13

per band, detector, and mirror-side

• M11

, M12

, M13

= f (scan angle), cubic (M11) and linear (M12)

• do this for one day per month over the mission lifespan

• optimize over global distribution of path geometries

Lm: MODIS measured TOA radiance (without polarization corr.)

LTOA: modeled (nLw from SeaWiFS, aerosols from MODIS NIR bands)

Q, U: Stokes vector parameters (modeled from Rayleigh)

6

M12: MODIS Terra blue band temporal trends

Mirror side 2

Detector 4

Mirror side 1

Space View (lunar) frameNadir frame

Solar Diffuser frame

412

443

488

M12 acts onthe Q component

7

M13 fixed to pre-launch412

443

488

Blue band RVS & polarization sensitivity MS1, Detector 4

8

9

10

More microwave sensitivities: to rain

11

Aerosol sensitivity to surface albedo

A “critical surface albedo” exists for which sensitivity to aerosol completely disappears!

Seidel & Popp, AMT, 2012

ϖ0

12

Aerosol sensitivity to surface albedo

A “critical surface albedo” exists for which sensitivity to aerosol completely disappears!

Seidel & Popp, AMT, 2012

AOD retrieval error at 550 nm. Plus (minus) signs denote an overestimate of surface albedo by 0.01 (-0.01).

13

Sensitivity studies: useful for lots of things

• Impact of instrument errors on retrievals

• Best channels to retrieve certain variables

• Qualitative picture of retrieval errors vs. different quantities (e.g. aerosol vs. surface albedo)

• Impact of uncertainties in other variables on retrievals: e.g. cloud temperatures on cloud water path from Vis/NIR.

14

15

2D Gaussian