iop algorithm workshop, ocean optics xix, 3-4 oct 2008, pjw nasa/ssai iop algorithm workshop @ ooxix

IOP Algorithm Workshop, Ocean Optics XIX, 3-4 Oct 2008, PJW

NASA/SSAI

IOP Algorithm Workshop @ OOXIX

NASA/SSAI

Fri / Sat workshop generic agenda:

9:00 start

10:30 break

12:30 lunch

13:30 resume

15:30 break

17:30 end

22:00 group dinner (Fri)

NASA/SSAI

focus topics:

1. overview

2. end-user perspectives

3. operational implementation strategies

4. relationships between Rrs and IOPs

5. regional adjustment of SAA parameterization

6. new directions

7. summary, recommendations, & steps forward

NASA/SSAI

topic 1 - overview (mod by Jeremy)

topics:

summarize goals, approaches, evaluation process, & limitations

goals:

clear understanding of workshop goals

agreement on evaluation process & metrics

agreement on accuracy of SAA summaries

recognition of overlap amongst approaches

NASA/SSAI

what we’re (NASA, anyway) looking to do:

extend the IOCCG SAA survey by

(1) evaluating application of SAA algorithms to satellite radiometry

(2) reviewing & consolidating SAA construction

workshop motivation & goal:

achieve community consensus on an effective algorithmic approach for producing global-scale, remotely sensed SAA IOP products

what we’re (NASA, anyway) looking for:

combination of accuracy and geographic coverage

flexible, multi-sensor implementation

computational efficiency to support operational environment

open source software and accompanying LUTs

associated SAA uncertainties

NASA/SSAI

algorithm “sh

oot out”

you’ve been warned:

NASA/SSAI

topics:

goals:

NASA/SSAI

process:

SAA identification: literature review (IOCCG report 5); community solicitation

SAA consolidation: identification of (dis)similarities

software accumulation: standalone versions & l2gen (SeaDAS) import

evaluation prep: define metrics; design analyses; identify test data sets

“validation” analyses

sensitivity studies

community dialog

workshop: consolidate recom-mendations; ideas

NASA/SSAI

pre-workshop achievements - overview

1. process: a philosophy & a path forward

2. software: l2gen (msl12) & l3gen & IDL, Matlab, C, etc.

3. dialog: public record of (forum for) issues & ideas

4. shared analyses (evaluation, sensitivity, etc.)

NASA/SSAI

pre-workshop achievements - dialog & discussion

1. air-sea transmission, Rrs rrs(0-)

2. calculation of Rrs (bandpass correction, f/Q)

3. temperature & salinity dependence of aw & bbw

4. spectral data products to be considered (adg, bb, etc.)

5. evaluation metrics & SAA failure conditions

6. inversion methods & linearization issues

7. calculation of uncertainties

8. SAA product validation & sensitivity analyses

9. strategies to produce level-3 products

http://oceancolor.gsfc.nasa.gov/forum/oceancolor/board_show.pl?bid=24

NASA/SSAI

pre-workshop achievements - analyses

1. in situ-to-in situ & satellite-to-in situ match-ups

2. global (level-3) comparisons

3. spatial coverage (level-2) comparisions

4. sensitivities to parameterization & noisy input

5. sensitivity to inversion method

6. level-2 vs. level-3 inversion

http://oceancolor.gsfc.nasa.gov/MEETINGS/OOXIX/IOP/analyses.html

NASA/SSAI

available metrics:

posted analyses …

( for 400 < < 700 )

Rrs() > 0

adg() & a() > -0.005

bbp() > -0.0001

coverage …

retrieval quality / comparison …

available metrics:

level-3 flagging …

( for 400 < < 600 )

Rrs() > 0 (?)

-0.95 aw() < a() < 5

-0.05 aw() < adg() < 5

-0.05 aw() < a() < 5

-0.95 bbw() < bb() < 0.015

-0.05 bbw() < bbp() < 0.015

NASA/SSAI

topics:

goals:

NASA/SSAI

anatomy of a semi-analytical algorithm (SAA):

many approaches are similarly constructed & parameterized

next, I’ll deconstruct the SAAs to illustrate similarities & differences

the goal is to convince you that most SAAs fall within 2 / 3 categories of construction & that most have interchangeable parts

NASA/SSAI

Rrs =ℜfQ

a + bb

⎝ ⎜

⎠ ⎟

satellite provides Rrs()

a () and bb () are desired products

bb = bbw + bbii=1

a = aw + aii=1

total a and bb are sums of coefficients for all components in seawater

=bbw + M i bbii=1

=aw + M i a ii=1

each coefficient expressed as product of magnitude and spectral shape

=aw + M dgadg + Mφaφ

bb = bbw + bbp

=bbw + Mbpbbp

a = aw + adg + aφ

adg = exp S λ 0 − λ[ ]( )

bbp = λ η

aφ λ( )

NASA/SSAI

adg = exp S λ 0 − λ[ ]( )

bbp = λ η

aφ λ( )

NASA/SSAI

GSM, HL, BR

ℜ f /Q

Gordon quad;Lee trans

adg = exp S λ 0 − λ[ ]( )

bbp = λ η inversion

variable S variable

simultaneous:nonlinear (L-M), matrix inversion

a variable

rrs (0− ,λ ) ≈

bbw (λ )+ Mbpbbp (λ )

aw (λ )+ M dgadg (λ )+ Mφaφ (λ )+ bbw (λ )+ Mbpbbp (λ )

system of 5/6 equations with 3 unknowns

NASA/SSAI

a = a - aw - adg

calculate a

empiricala(555)

iterationa(i,j)

estimate adg(i) usingS, adg(i,j), and a(i,j)

PML, NIWA

ℜ f /Q

bbp = λ η

variablecalculate a

adg = exp S λ 0 − λ[ ]( )

NASA/SSAI

solution

bb and a both fromKd, bw/b, and solz

ℜ f /Q calculate Kd

NASA/SSAI

GSM, HL, BR

ℜ f /Q

a = a - aw - adg

adg = exp S λ 0 − λ[ ]( )

bbp = λ η inversion

variable S variable

simultaneous:nonlinear (L-M), matrix inversion

a variable

calculate a

empiricala(555)

iterationa(i,j)

estimate adg(i) usingS, adg(i,j), and a(i,j)

solution

bb and a both fromKd, bw/b, and solz

PML, NIWA

ℜ f /Q

bbp = λ η

variablecalculate a

adg = exp S λ 0 − λ[ ]( )

ℜ f /Q calculate Kd

NASA/SSAI

current state-of-the-art:

NASA/SSAI

algorithm #1

bal deep w

adg(555)retrievals

adg(555)difference

NASA/SSAI

topics:

goals:

NASA/SSAI

GSM (standard)

standard

NASA/SSAI

GSM (QAA , QAA S, Bricaud a )

standard

NASA/SSAI

GSM (standard)

NASA/SSAI

GSM (standard)

NASA/SSAI

topic 2 - end-user perspectives (mod by Mike)

topics:

desired products & their uses

accuracy / behavior uncertainty requirements

goals:

list(s) near- & long-term needs (with attention to what’s available)

list(s) of data product hierarchy / priority

NASA/SSAI

topic 3 - operational implementation strategies (mod by Bryan)

topics:

L2 Rrs - l2gen, f/Q & normalization, bandpass corrections

L3 IOPs - masks, geometry, calc @ L2 vs L3, other strategies

goals:

consensus understanding of L2 Rrs generation

agreeement on SAA flags & their use in L3 product generation

discussion of (dis)advantages of product generation at L2 vs. L3

NASA/SSAI

topic 4 - relationships b/w Rrs and IOPs (mod by Emmanuel)

topics:

IOP shape functions; inversion procedures; uncertainties; ambiguity

goals:

discussion of sensitivities of shape functions & inversion procedures & how they impact product accuracies & geographic coverage

discussion of methods for uncertainty determination

NASA/SSAI

topic 5 - regional adjustment of SAA params (mod by Mark/Tim)

topics:

Dowell/Moore optical water type classification approach; others?

goals:

consensus (dis)agreement of need to pursue such approaches

NASA/SSAI

topic 6 - new directions (mod by Samantha)

topics:

GlobColour; fluorescence; f/Q & normalization(s); others?

goals:

illumination

NASA/SSAI

backup slides

NASA/SSAI

questions to be answered:

1. SAAs predefine spectral shapes for the IOP products of interest. What are the key components & can their sensitivities, uncertainties, & relative priority be defined?

2. How critical / sensitive is the optimization or inversion method used?

3. How does spectral resolution effect the retrievals?

4. How do the SAAs perform:

a. relative to in situ IOPs using in situ Rrs?

b. relative to in situ IOPs using satellite Rrs (from a match-up data set)?

c. on various satellite level-2 & level-3 scenes

5. Do the conclusions of #1-4 vary by trophic level or bioregime?

6. What are the remediations to failure?

7. What is the most appropriate implementation strategy for operational satellite data processing (e.g., level-2 Rrs normalization, masking & binning at level-3?

NASA/SSAI

topic 2 - end-user perspectives (mod by Mike)

recommendations:

NASA/SSAI

topic 3 - operational implementation strategies (mod by Bryan)

recommendations:

NASA/SSAI

topic 4 - relationships b/w Rrs and IOPs (mod by Emmanuel)

recommendations:

NASA/SSAI

topic 5 - regional adjustment of SAA params (mod by Mark/Tim)

recommendations:

NASA/SSAI

topic 6 - new directions (mod by Samantha)

recommendations:

NASA/SSAI

(dis)advantages of various modeling approaches:

empirical

straightforward (Rrs product) & computationally efficient

biased to in situ database & degrades with optical complexity

SAA / quasi-SAA

configurable form & simultaneous output of multiple products

only as representative as model assumptions (including empirical functions)

based on exact RTE calculations & simultaneous output of products

only as representative and flexible as RTE model assumptions

NASA/SSAI

attendees:

Antoine Mangin (ACRI) Odile Hembise Fanton d’Andon (ACRI)

Bryan Franz (NASA) Paula Bontempi (NASA)

Catherine Brown (LOV) Samantha Lavender (U. Plymouth)

Emmanuel Boss (U. Maine) Sean Bailey (NASA)

Gene Feldman (NASA) Stephane Maritorena (UCSB)

Hubert Loisel (U. Littoral) Takafumi Hirata (PML)

Jeremy Werdell (NASA) Tim Moore (NURC)

Jill Schwarz (NIWA) Tim Smyth (PML)

Mark Dowell (JRC) Yannick Huot (LOV)

Mike Behrenfeld (OSU) ZhongPing Lee (MSU)

unable to attend: Andre Morel (LOV), Paul Lyon (NRL)

NASA/SSAI

Rrs =ℜfQ

a + bb

⎝ ⎜

⎠ ⎟

adg = exp S λ 0 − λ[ ]( )

bbp = λ η

bb = bbw + bbi = bbw + M i bii=1

∑i=1

a = aw + adg + aφ = aw + M dgadg + Mφaφ

a = aw + ai = aw + M i a ii=1

∑i=1

bb = bbw + bbp = bbw + Mbpbbp

rrs (0− ,λ ) ≈

bbw (λ )+ Mbpbbp (λ )

aw (λ )+ M dgadg (λ )+ Mφaφ (λ )+ bbw (λ )+ Mbpbbp (λ )

iop algorithm workshop, ocean optics xix, 3-4 oct 2008, pjw nasa/ssai iop algorithm workshop @ ooxix

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