Fluorescence Line Height (FLH)

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Fluorescence Line Height (FLH)

• Ricardo Letelier,
• Mark Abbott,
• Jasmine Nahorniak
• Oregon State University

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Outline

• FLH basic alghorithm
• Comparison between field measurements and MODIS
  FLH
• FLH and chl a
• Chlorophyll Fluorescence Efficiency

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Acknowledgments

• Mark Abbott, Jasmine Nahorniak (OSU)
• Dennis Clark (NOAA)
• Wayne Esaias, Frank Hoge (NASA)
• Bob Evans, Kay Kilpatrick, Howard Gordon, Ed
  Kearns (Univ. Miami)
• Ken Carder (USF)
• John Cullen Yannick Huot (Dalhousie)

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Chlorophyll absorption
Increase in fluorescence
F PAR x (chl x a) x Ff
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MODIS FLH bands avoid oxygen absorbance at 687
nm
Weighting factor used to compensate for
off-center FLH
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0.12
FLH (10 mg)
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0.10
10 mg
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0.08
0.01 mg
Radiance, W m-2 µm-1 sr-1
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0.06
Normalized band transmittance
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0.04
Negative FLH due to TOA curvature needs to be
corrected empirically
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0.02
0
0.00
650
670
690
710
730
750
770
l13
l14
l15
Wavelength, nm
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Field Observations

• In situ open ocean
• - MOBY
• - HOT cruises
• -In situ Coastal
• - GLOBEC
• - COAST
• - Southern Ocean

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• Optical Drifters
• 29 off Oregon
• 12 in the Southern Ocean
• Noth Atlantic
• (John Cullens group)

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http//picasso.coas.oregonstate.edu/ORSOO/
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Testing the MODIS FLH Algorithm
FLH vs. chlorophyll
FLH vs. CDOM
From Hoge et al.
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GLOBEC NEP AUGUST 2002
FLH, W m-2 µm-1 sr-1
chl .021 43.4 FLH1.866
In situ chlorophyll, mg m-3
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GLOBEC NEP AUGUST 2002
chlFLH semi-analytical (Huot Cullen assuming
ff 0.006)
chlFLH empirical (this study)
In situ chl

• Both FLH derived chl algorithms appear to
  slightly overestimate chl a fields.
• They do not seem to reproduce the low values
  observed in situ.
• Some of the differences between in situ and FLH
  derived could be due to time differences and
  sampling depth (in situ 5 m depth)

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GLOBEC NEP AUGUST 2002 (July 31st August
19th)
In situ chl a, mg m-3
MODIS chl a_2, mg m-3
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In Situ Observations of F/chl suggest it can be
a proxy for ff
Initial slope proportional to ?F
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MODIS Terra L2 1 km resolution scene from
October 3rd 2001
Sea Surface Temperature Chl a Chl
Fluorescence Line Height (C) (mg m-3)
(W m-2 mm-1 sr-1)
From OSU-COAS EOS DB Station
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Seasonal patterns of FLH and chl a
Southern Ocean
Indian Ocean
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chlFLH empirical (this study)
Huot Cullen ARP using in situ chl to Derive an
average ff
MODIS ARP
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GLOBEC NEP AUGUST 2002
chlFLH empirical (this study)
MODIS CFE using Huot Cullen ARP
MODIS CFE using MODIS ARP
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Thalassiosira weissflogii Chemostat results
2001-2002
After 3 days of constant cell counts After 14
days
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Where do we stand?

• Field observations suggest that MODIS FLH is a
  robust product.
• Comparison of chlfield vs FLHMODIS suggest
  that FLH may prove of use to derive chl in
  turbid waters. However, and as expected, there is
  no single relation between FLH and chl a. (See
  also K Carder poster).
• CFE validation requires that of FLH and ARP.
• In order to interpret CFE we need field and
  laboratory based work that explores the effect of
  environmental variability and phytoplankton
  specific composition.

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FLH working group

• Charlie Yentsch (CSYentsch_at_aol.com),
• Dave Siegel (davey_at_icess.ucsb.edu),
• Greg Leptoukh (Gregory.Leptoukh_at_nasa.gov),
• Richard Sikorski (sikorski_at_raytheon.com),
• Chuck McClain (Charles.R.McClain_at_nasa.gov),
• Heidi Dierssen (heidi.dierssen_at_uconn.edu),
• Chuanmin Hu (hu_at_seas.marine.usf.edu),
• Paula Bontempi (paula.s.bontempi_at_nasa.gov),
• Alex Cunningham (a.cunningham_at_strath.ac.uk),
• Mike Behrenfeld (Mike.Behrenfeld_at_nasa.gov),
• Ricardo Letelier (letelier_at_coas.oregonstate.edu)