Statistical Inversion Algorithm for MODIS AOD Retrieval...MODIS AOD retrieval was developed Signiﬁcantly improves the accuracy of retrieved AOD in most of test areas 1.Spatial correlation

Statistical Inversion Algorithm forMODIS AOD RetrievalAntti [email protected]

Finnish Meteorological InstituteYoram Kaufman Memorial SymposiumJune 21, 2016

• Tero Mielonen (FMI)

• Mikko Pitkänen (FMI)

• Rob Levy (GSFC)

• Ville Kolehmainen (UEF)

• Sami Romakkaniemi (FMI)

• Antti Arola (FMI)

A. Lipponen: Statistical Inversion for MODIS AOD Retrieval

Typical granule: 27 September 2009







AERONET stations0.00

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AO

D

AERONET




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AO

D

AERONETDark Target




0.05

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AO

D

AERONETDark TargetNew




0.05

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AO

D




0.00

0.05

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AO

D

sum(|error|) ≈ 0.53

sum(|error|) ≈ 0.30



New retrieval algorithm

1. Statistical (Bayesian) inversion

2. Modified surface reflectance relationship

3. Quantities retrieved

• AOD

• fine mode fraction

• surface reflectances at 466 and 644 nm






• AOD








• AOD








• AOD








• AOD





Figure from http://darktarget.gsfc.nasa.gov/algorithm/land



Figure from http://darktarget.gsfc.nasa.gov/algorithm/land


1. Statistical inversion

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4AOD τ

Pro

babi

lity

dens

ity fu

nctio

n va

lue

π(τ|ρ) =π(ρ|τ)π(τ)π(ρ)

Bayes' theorem



0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4AOD τ

Pro

babi

lity

dens

ity fu

nctio

n va

lue


Prior distribution π(τ)



0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4AOD τ

Pro

babi

lity

dens

ity fu

nctio

n va

lue


Prior distribution π(τ)Likelihood distribution π(ρ|τ)



0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4AOD τ

Pro

babi

lity

dens

ity fu

nctio

n va

lue


Prior distribution π(τ)Likelihood distribution π(ρ|τ)Posterior distribution π(τ|ρ)


1. Statistical inversion - prior distributions


1. Statistical inversion - prior distributionsFebruary

September


1. Statistical inversion - likelihood distributions


1. Statistical inversion - likelihood distributions

ρ = f (τ, η, ρs0.466, ρs

0.644) + e

• Radiative transfer model• Lookup tables from Dark Target

• Gaussian noise model for e

• Results in Gaussian likelihood distribution





Original figure from Levy, Remer, Mattoo, Vermote and Kaufman, JGR, 2007.


















0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35Input surface reflectance

0.00

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Out

puts

urfa

cere

flect

ance

2.1µm→ 0.644 µm0.644µm→ 0.466 µm




0.00

0.05

0.10

0.15

0.20

Out

puts

urfa

cere

flect

ance

2.1µm→ 0.644 µm0.644µm→ 0.466 µmmodified 2.1µm→ 0.644 µmmodified 0.644µm→ 0.466 µm


3. Quantities retrieved - AOD, FMF, ρs × 2


3. Quantities retrieved - AOD, FMF, ρs × 2


0.00

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Out

puts

urfa

cere

flect

ance

modified 2.1µm→ 0.644 µmmodified 0.644µm→ 0.466 µm


Results


Results

Europe

SouthAmericaSouthAfrica

NorthAmerica

SouthAsia


Results

Europe

SouthAmericaSouthAfrica

NorthAmerica

SouthAsia


Results - North America

• 15 granules / month (180 granules)

• Total of 656 AERONET comparisons





0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8AOD (AERONET)

0.0

0.2

0.4

0.6

0.8

AO

D (M

OD

IS)

Inside ±0. 05± 0. 15 ∗AODAERONET envelope: 49.1%Median absolute error: 0.066

Bias: 0.076

DARK TARGET



0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8AOD (AERONET)

0.0

0.2

0.4

0.6

0.8

AO

D (M

OD

IS)

Inside ±0. 05± 0. 15 ∗AODAERONET envelope: 66.8%Median absolute error: 0.042

Bias: 0.020

NEW


Results - Median absolute error in AOD

0.00 0.02 0.04 0.06 0.08 0.10Median absolute error in AOD

South Asia

North America

South America

Europe

Overall




South Asia

North America

South America

Europe

OverallDark Target




South Asia

North America

South America

Europe

OverallDark TargetNew




South Asia

North America

South America

Europe

Overall

1%

36%

9%

12%

18% Dark TargetNew


Results - Bias in AOD

0.02 0.00 0.02 0.04 0.06 0.08Bias in AOD

South Asia

North America

South America

Europe

Overall



0.02 0.00 0.02 0.04 0.06 0.08Bias in AOD

South Asia

North America

South America

Europe

OverallDark Target



0.02 0.00 0.02 0.04 0.06 0.08Bias in AOD

South Asia

North America

South America

Europe

OverallDark TargetNew


Conclusions

• A statistical inversion based inversion algorithm forMODIS AOD retrieval was developed

• Significantly improves the accuracy of retrieved AODin most of test areas

1. Spatial correlation models


3. Surface reflectance is estimated in additionto AOD and FMF


Conclusions







Conclusions







Conclusions

• Manuscript under preparation, will be submitted soon

• Code package (Python) will be released with the paper• Want early access to the codes? Please ask

[email protected]

• Want to try the algorithm e.g. with differentinstrument or in retrieval of other quantities?

• Have ideas to further develop theinversion algorithm?

• All comments, ideas, etc. are very welcome


Conclusions

• Manuscript under preparation, will be submitted soon

• Code package (Python) will be released with the paper• Want early access to the codes? Please ask

[email protected]

• Want to try the algorithm e.g. with differentinstrument or in retrieval of other quantities?

• Have ideas to further develop theinversion algorithm?

• All comments, ideas, etc. are very welcome


Thank you for your attention!

[email protected]

Documents

Statistical Inversion Algorithm for MODIS AOD Retrieval...MODIS AOD retrieval was developed Signiﬁcantly improves the accuracy of retrieved AOD in most of test areas 1.Spatial correlation