ISOPLETHS OF CHLOROPHYLL IN RADIANCE SPACE

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ISOPLETHS OF CHLOROPHYLL IN RADIANCE SPACE
Janet W. Campbell, Timothy S. Moore, and Mark D.
Dowell Ocean Process Analysis Laboratory Universi
ty of New Hampshire Durham, NH 03824-3525
USA Santa Fe, New Mexico November 21, 2002
This work was supported by a NASA MODIS
Team contract (NAS5-96063) and NASA grant
(NAG5-6289).
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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) maxR(443),R(490)R
(555) maxR(443),R(490),R(510)R(555)

• CZCS
• OC2
• OC3M
• OC4

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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

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Ratio algorithms are strongly supported by
empirical data.
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Isopleths of chlorophyll for the OC4 algorithm
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3-D constituent space maps into 2-D reflectance
plane
bbpbbp(555)
max. Rrs(l)
Chl
Rrs(555)
admacdm(443)
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Feasible Points in 490 vs. 555 Reflectance Plane
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SeaBAM Data
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Isopleths of Chl in the OC4 plane, holding adm
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Chl 0.3 isopleths varying adm between 0
and 90
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Chl 0.3 isopleths varying adm between 0
and 90
Tracing points along the OC4 Chl 0.3 isopleth,
adm increases as bbp decreases.
OC4
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SeaBAM data for Chl 0.1, 1 and 10
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Isopleths of chlorophyll for the OC4 algorithm
The GarverSiegel model was inverted to derive
the relationship between adm and bbp along the
OC4 isopleths of Chl.
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Relationship between adm and bbp required to
reconcile OC4 and GarverSiegel model
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SeaBAM Data
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Chl lt 0.05 Chl 0.1 Chl 1 Chl
10
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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.

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CONCLUSIONS (cont.)

• 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.
• This might contain a clue as to the nature of the
  particles that scatter light in the different
  ocean environments.

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NOMAD Data
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SeaBAM Data
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