isopleths of chlorophyll in radiance space janet w. campbell, timothy s. moore, and mark d. dowell...
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ISOPLETHS OF CHLOROPHYLL IN RADIANCE SPACE
Janet W. Campbell, Timothy S. Moore, and Mark D. Dowell
Ocean Process Analysis LaboratoryUniversity of New Hampshire
Durham, NH 03824-3525 USA
Santa Fe, New MexicoNovember 21, 2002
This work was supported by a NASA MODIS Teamcontract (NAS5-96063) and NASA grant (NAG5-6289).
According to a ratio algorithm….
Isopleths of chlorophyll are lines passing through the origin in the plane defined by the two
radiances used in the ratio.
Lw(443):Lw(550)
R(490):R(555)
max[R(443),R(490)]:R(555)
max[R(443),R(490),R(510)]:R(555)
• CZCS
• OC2
• OC3M
• OC4
According to a semi-analytic algorithm …
Isopleths of chlorophyll generally do not pass through the origin
in planes defined by two radiances.
• Gordon et al. 1988
• Garver & Siegel, 1997
• Carder et al. 1999
)(b)(a
)(b~)(R
b
brs
In this presentation, I will….
1. Demonstrate this by comparing
• Garver & Siegel (1997) algorithm
• OC4 algorithm (O’Reilly et al. 2000)
2. Show that covariance among optically active constituents reconciles this inconsistency.
Ratio algorithms are strongly supported by empirical data….
OC4
0
0.01
0.02
0.03
0.04
0 0.01 0.02 0.03 0.04
Normalized reflectance at 555
Max
imum
ref
lect
ance
Chl = 0.01 0.1 0.3 1
3
10
30
Isopleths of chlorophyll for the OC4 algorithm
Gordon et al. 1988
p
bp555
)(b
(555)bbp
)(a)(a)(a)(a cdmphw )(B
ph )(A)(a
Chl
)]443(Sexp[)(acdm (443)acdm
)(b)(b)(b bpbwb
Bricaud et al. 1995
)(b)(a
)(b~)(R
b
brs
S = 0.02
p = 1
Pope & Fry, 1997
Semi-analytic Model of Garver & Siegel, 1997
bbp=bbp(555)
adm=acdm(443)
Chl
Rrs(555)
max
. Rrs(
)
3-D “constituent space” maps into 2-D reflectance plane
%100)443(a
(443)a
%adm cdm
0
0.002
0.004
0.006
0.008
0.01
0.012
0.014
0 0.002 0.004 0.006 0.008 0.01
Rrs(555)
Rrs
(490
)
Pure Seawater
Chl = 0 %adm = 0
p=2 to 0
Chl = 10 mg m-3
%adm = 80%
bbp = 0
Feasible Points in 490 vs. 555 Reflectance Plane
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.000 0.002 0.004 0.006 0.008 0.010
Rrs(555)
Rrs
(490
)
0.025
0.040
0.063
0.10
0.16
0.25
0.40
0.63
1.0
1.6
2.5
4.0
6.3
10
12-33
pure seawater
a=aw, p=2
a=aw, p=0
chl=10, %adm=80%
bbp=0
Measured Chl
SeaBAM Data
Chl = 0.01 0.1 0.3 1 3
10, 30
Garver&Siegel Model%adm = 35%
0.00
0.01
0.02
0.03
0.04
0.00 0.01 0.02 0.03 0.04
Normalized reflectance at 555
Max
imum
ref
lect
ance
Max
imum
ref
lect
ance
Isopleths of Chl in the OC4 plane, holding %adm = 35%
bbp isopleths
0.00
0.01
0.02
0.03
0.04
0.00 0.01 0.02 0.03 0.04
Normalized reflectance at 555
Max
imum
ref
lect
ance
Garver & Siegel ModelChl = 0.3
%adm = 0 10 35 50 65 80
90
Chl = 0.3 isopleths varying %adm between 0 and 90%
bbp isopleths
0.00
0.01
0.02
0.03
0.04
0.00 0.01 0.02 0.03 0.04
Normalized reflectance at 555
Max
imum
ref
lect
ance
Garver & Siegel ModelChl = 0.3
%adm = 0 10 35 50 65 80 90
OC4
Chl = 0.3 isopleths varying %adm between 0 and 90%
Tracing points along the OC4 Chl = 0.3 isopleth, adm
increases as bbp decreases.
Garver&Siegel Model
0.00
0.01
0.02
0.00 0.01 0.02
Normalized reflectance at 555
Max
imum
ref
lect
ance
%adm = 0% 10% 50% 10% 75%
Chl = 10
90%
30%
Chl = 0.1 Chl = 1Chl = 0
SeaBAM data for Chl = 0.1, 1 and 10
OC4
0
0.01
0.02
0.03
0.04
0 0.01 0.02 0.03 0.04
Normalized reflectance at 555
Max
imum
ref
lect
ance
Chl = 0.01 0.1 0.3 1
3
10
30
Isopleths of chlorophyll for the OC4 algorithm
The Garver&Siegel model was inverted to derive the relationship between adm and bbp along the
OC4 isopleths of Chl.
0.001
0.01
0.1
1
10
0.0001 0.001 0.01 0.1 1
bbp
adm
Chl=0.1
Chl=0.3
Chl=1
Chl=3
Chl=10
Chl=30
Relationship between adm and bbp required to reconcile OC4 and Garver&Siegel model
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.000 0.002 0.004 0.006 0.008 0.010
Rrs(555)
Rrs
(490
)
0.025
0.040
0.063
0.10
0.16
0.25
0.40
0.63
1.0
1.6
2.5
4.0
6.3
10
12-33
pure seawater
a=aw, p=2
a=aw, p=0
chl=10, %adm=80%
bbp=0
Measured Chl
SeaBAM Data
y = 0.0017x-0.2437
R2 = 0.1553
y = 0.0213x-0.1004
R2 = 0.0336
y = 22.758x1.0451
R2 = 0.7064
y = 0.0002x-0.5021
R2 = 0.2868
0.001
0.01
0.1
1
10
0.0001 0.001 0.01 0.1
bbp
adm
Chl < 0.05 Chl = 0.1 Chl = 1 Chl = 10
CONCLUSIONS
1. According to semi-analytic models for Case 1 waters, optical properties are governed by three variables (Chl, adm, bbp). Chl isopleths in radiance space do not pass through the origin.
2. Empirical evidence supports ratio algorithms in which Chl isopleths do pass through the origin.
3. Covariance between adm and bbp reconciles this discrepancy.
CONCLUSIONS (cont.)
4. The nature of the relationship between adm and bbp depends on the trophic state:
• In oligotrophic waters, there is a negative correlation between adm and bbp.
• In eutrophic waters, the correlation is zero or positive.
5. This might contain a clue as to the nature of the particles that scatter light in the different ocean environments.
0.000
0.005
0.010
0.015
0.020
0.025
0.030
0.000 0.005 0.010 0.015 0.020 0.025 0.030
<0.02
0.025
0.040
0.063
0.10
0.16
0.25
0.40
0.63
1.0
1.6
2.5
4.0
6.3
10
>12
pure water
a=aw
bbp=0
Chl=10
NOMAD Data
0.000
0.002
0.004
0.006
0.008
0.010
0.012
0.014
0.000 0.002 0.004 0.006 0.008 0.010
Rrs(555)
Rrs
(490
)
0.025
0.040
0.063
0.10
0.16
0.25
0.40
0.63
1.0
1.6
2.5
4.0
6.3
10
12-33
pure seawater
a=aw, p=2
a=aw, p=0
chl=10, %adm=80%
bbp=0
Measured Chl
SeaBAM Data
