sensing primary production from ocean color: puzzle pieces and their status
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Sensing primary production from ocean color: Puzzle pieces and their status. ZhongPing Lee University of Massachusetts Boston. An effort started half century ago …. From over 7000 measurements. Global PP:. ~15 Gt /year. Longhurst et al (1995): 45-50 Gt C year -1 - PowerPoint PPT PresentationTRANSCRIPT
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Sensing primary production from ocean color: Puzzle pieces and their status
ZhongPing LeeUniversity of Massachusetts Boston
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An effort started half century ago …
~15 Gt/year
From over 7000 measurements
Global PP:
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Longhurst et al (1995): 45-50 Gt C year-1
Antoine et al (1996): 36.5-45.6 Gt C year-1
Behrenfeld and Falkowski (1997): 43.5 Gt C year-1
~3 times higher than estimates in the 50-60s’!
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(Behrenfeld et al 2005)
Large spatial differences from different sensing models
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Puzzle pieces to sense PP in the ocean
(Platt and Sathyendranath, 2007)
3. Phytoplankton index2. Light at depth
4. Energy conversion
(spectral attenuation)
(nutrient)
1. Input energy
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1. Input energy
(Frouin et al 1989, 2003)
PAR (Photosynthetic Available Radiation)
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Spectral irradiance
(Gregg and Carder 1990)
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zKdd
deEzE )()0,(),(
Q: How to get Kd(λ) of varying water bodies?
2. Light at depth(spectral attenuation)
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Rrs
Method 1:empirical
Rrs(λ1)/Rrs(λ2)
Algorithms to get Kd
Current operational standard
Rrs [Chl]
Method 2: empirical empirical
Rrs(λ1)/Rrs(λ2)
KddK
Kd )490(dK
Rrs a&bb
Method 3: semi-analytical semi-analyticalKddK
(QAA)
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Kd(490) - measured [m-1]
0.03 0.05 0.3 0.5 3 50.1 1
K d(49
0) [
m-1]
0.03
0.05
0.3
0.5
3
5
0.1
1
1:1Arabian SeaGOMBaltic
(b: Method 2)
Kd(490) - measured [m-1]
0.03 0.05 0.3 0.5 3 50.1 1
Kd(
490)
[m
-1]
0.03
0.05
0.3
0.5
3
5
0.1
1
1:1Arabian SeaGOMBaltic
)49
0(dK
)490(dK
)49
0(dK
Kd(490) - measured [m-1]
0.03 0.05 0.3 0.5 3 50.1 1
Kd(
490)
[m
-1]
0.03
0.05
0.3
0.5
3
5
0.1
1
1:1Arabian SeaGOMBaltic
(a: Method 1)
)49
0(dK
)490(dK )490(dK
(c: Method 3)
(Lee et al. 2005)
Oceanic &Coastal waters
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Wavelength [nm]
Spec
tral
Kd
[m-1
]
X Data
350 400 450 500 550
Y D
ata
0.00
0.02
0.04
0.06
0.08
measuredsensed
X Data
0.03 0.30.01 0.1 1
Y D
ata
0.03
0.3
0.01
0.1
11:1IOP
IOPs
-Kd(4
90)
[m-1
]
Profile Kd(490) [m-1]
The NOMAD set (1243 data points)
Kd through IOPs
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Profile-Kd(490) [m-1]
Ratio
-der
ived
Kd(4
90)
[m-1
]
X Data
0.00 0.05 0.10 0.15 0.20
Y D
ata
0.00
0.05
0.10
0.15
0.20
0.25
< 301.0930-600.99> 600.89
IOP-
base
d K d(4
90)
[m-1
]
Profile-Kd(490) [m-1]X Data
0.00 0.05 0.10 0.15 0.20
Y D
ata
0.00
0.05
0.10
0.15
0.20
0.25
< 300.9930-601.00> 601.00
Different sun angles:
Empirical ratio Through IOPs
How Kd in the UVA/UVB varies globally?Challenges:
Spectral Kd can be well derived based on physics!
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(Behrenfeld and Falkowski, 1997)
VGPM:
Chl became the index!!
3. Phytoplankton index
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Essence of Rrs-ratio derived Chl product:
b
brs ba
bGR
)550()550()440()440(
)440()550(
)550()440(
bpbw
bpbw
rs
rs
bbbb
aa
RR
ChlaaaChlaaa
aa
RR
phdgw
phdgw
rs
rs
)440()440()440()550()550()550(
)440()550(
)550()440(
*
*
)()(
2
1
rs
rs
RRfunChl
Simple ratio actually involves more than one variable!
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(Szeto et al 2011, JGR) Simple ratio dismissed spatial/temporal variation!
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Nature of ratio-derived “Chl”
At the center of South Pacific Gyre
May 2009, Global, MODIS
Ratio-derived “Chl” is re-scaled total absorption coefficient!
Rrs
-rat
io d
eriv
ed C
hl [
mg/
m3 ]
Analytically derived a(443) [m-1] Rrs
-rat
io d
eriv
ed C
hl [
mg/
m3 ]
Analytically derived a(443) [m-1]
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(Behrenfeld and Falkowski 1997)
4. Energy conversion
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(Platt et al, RSE, 2008)
Variation of phytoplankton- (or chlorophyll-) specific absorption coefficient (a*ph) contributes largely to the variation of PB
opt.
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DLzChlPARPPP euBopteu
DLzaPARPP eupheu
Centered on Chl
Centered on absorption
Both PBopt and Chl have a*ph associated
Increase uncertainty in PP
No engagement of a*ph
“Site-specific and previously published global models of primary production both perform poorly and account for less than 40% of the variance in ʃPP,” (Siegel et al 2001)
“significant improvements in estimating oceanic primary production will not be forthcoming without considerable advance in our ability to predict temporal and spatial variability in PB
opt”. (Behrenfeld and Falkowski 1997)
Chl is NOT the direction to go.
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PP estimation based on phytoplankton absorption (aph):
Ocean color aph PP
dtdzaztEztzPP ph ),(),,(),()( 0
Phytoplankton index
Quantum yield for photosynthesisRemotely sensible
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(Marra et al 2007, Deep Sea Res.)
R2 = 0.84 R2 = 0.78
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0
0bpbp )()( bb
Rrs()
)()( 0 aa
)(),(),(F)( 0bw0020bp baub
)(),(),(F)( bwbp3 bbua
η (± Δη)
)(F)( 1 rsRu
))(),(),(),((F)(
))(),(),(),((F)(
2152
2142
aaa
aaa
dg
ph
U1
U2
U3 U4
(Lee et al. Appl. Opt., 2002)The Quasi-analytical algorithm (QAA)
)()()()(
b
b
babu
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a ph(λ
) (m
-1)
(Lee et al 2004)
Measured vs sensed aph
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measured production (mol/l/day)0.3 31 10
calc
ulat
ed p
rodu
ctio
n (
mol
/l/da
y )
0.3
3
1
10 aph-centeredChl-centered1:1
(Lee et al. 1996)(Lee et al. 2010)
Absorption-based PP compared with measured PP
100 200 300 400 500 600 700100
200
300
400
500
600
700
Chl-PPB
Chl-PPA
Aph-PP
R2 = 0.29
R2 = 0.74
PPeu from on-deck incubation [mg C m-2 d-1] PP
eufr
om m
odel
[m
g C
m-2
d-1 ]
1:1R2 = 0.44
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Where is the global model for φ?
Challenges:
Which ‘ground truth’ we remote-sensors should aim at?
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Summary:1. A frame work for sensing primary production is well established.
2. Optical/light related parameters can now be well retrieved from satellite measurements, at least for oceanic waters.
3. Demands support and hard work to understand and quantify photo-physiological effects.
4. Demands true “ground truth”!
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Questions?