MODIS OCEAN NET PRIMARY PRODUCTION ONPP

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MODIS OCEAN NET PRIMARY PRODUCTION (ONPP)
W.E. Esaias, NASA GSFC K.R.TURPIE, D. THOMAS,
R. VOGEL, A. BHATTI September 5, 2003 Oregon
State University wayne.e.esaias_at_nasa.gov http//o
ppscf.gsfc.nasa.gov http//modis-ocean.gsfc.nasa.g
ov
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Primary Productivity Round Robin
Campbell et al., GBC (2002)
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Estimates of Primary Productivity
Most of the variability in estimates is due to
the uncertainty in the physiological parameters
in the models
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MODIS Ocean Net Primary Productionprovides
measure of C fixation by phytoplanktonW.E.
Esaias, NASA GSFC K.R.TURPIE, D. THOMAS, R.
VOGEL, A. BHATTI2 Models P1 and P2
P1 Behrenfeld Falkowski VGCM NPP f(Chl a,
PAR, Pb opt) Integrated over the Euphotic zone
(1) Pb opt f (SST) 7th order
polynomial P2 Howard, Yoder, Ryan NPP f
(Chl a, PAR, Pmax) Integrated over the upper
Mixed Layer Depth (MLD) Pmax (Platt) f (SST)
Eppley Peterson exponential Produced for 8-day
intervals at 4.6 km resolution. Binned files -
4.6 km equal area, Map files - 4.6 km , 36 km ,
1 degree in linear lat-lon fields - P1, P2, MLD,
PAR, SST, Chl parameters - mean, sd, n, N,
quality flags
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ONPP INPUT FIELDS
Chlor_a_3 MODIS Chlorophyll concentration
MLD (FNMOC) Mixed Layer Depth (for P2)
January 25, 2001
SSTD MODIS SST day
PAR (GSFC DAO) Photosynthetically Available
Radiaiton
January 25, 2001
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Independent Validation Study Gregg and
Casey NODC SeaBASS, L-3 4.6km Quality Level 0,
1 Chlor_a_2 virtually identical performance as
for SeaWiFS r2 0.757 n1.6K vs 0.759
ngt4.5K Semi-analytic Chlor_a_3 shows improvement
r2 0.784
Chlor-MODIS
Chlor_a_2
Chlor_a_3
Watson Gregg Nancy McCabe
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Level 3 Matchups
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Compare ONPP with Alternate MODIS Chlorophyll a
Products Compare MODIS ONPP with ONPP using
SeaWiFS Chlorophyll Run offline for Year
2001 Common Grid (Linear Maps) at 39 km, 8 day
averages (sampling effects determined by
comparing to Std 4.6 km binned data) Use Std
MODIS inputs MODIS daytime 11-12 m SST PAR from
GSFC DAO incident shortwave radiation FNMOC
Mixed Layer Depth Compare Standard Ocean Regions
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OCEAN PRODUCTIVITY from MODIS A New Baseline
Global average
Validated data period
Above Mixed layer Ocean Production Index
P2 Standard MODIS Product Collection 4
South Atlantic 10S to 50S
Compare Ocean Production using MODIS,
SeaWiFS, different chlorophyll algorithms
two production models MODIS Semi-analytic
chlorophyll results in 2 x greater production in
the key Southern Ocean regions, and phase
differences, global total between 57 and 59 GT C.
SeaWiFS/MODIS differences are relatively small.
Antarctic, S of 50S
Terra ONPP time series using chlorophyll from
SeaWiFS (green), MODIS Chlor_a_2(SeaWiFS analog)
(black), Chlor_MODIS(red), MODIS Chlor_a_3
Semi-analytic chlorophyll(blue) for global and 2
SO regions.
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3 MODIS Chlorophylls
MODIS Terra time series for oceans and
subregions, for three MODIS chlorophyll a
products. Chlor_a_2 is the SeaWiFS empirical
analog, Chlor-MODIS is Clarks empirical
algorithm Chlor_a_3 is Carders semi-analytic
algorithm it includes CDOM and pigment packaging
corrections.
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OPP P1, 4 Chlorophylls
Figure 7. ONPP P1 (B-F) computed with alternate
chlorophyll inputs, at 39 km resolution. NOTE
COLORS Blue Chlor_a_3, Red Chlor_MODIS,
Black Chlor_a_2, Green - SeaWiFS data.
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OPP STD PRODUCTS
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OPP P2, 4 Chlorophylls
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Table 1. Gigatons of carbon summed over the
oceanic regions for 2001, from 8-day time series,
corrected for average 11 non-sampled area, for
P1 and P2 with 4 chlorophyll inputs. Columns do
not sum due to included regions and round-off.
Right two columns were run at 4.6 km equal area
resolution, all others were run using 36 km
mapped resolution, corrected for projection
effects. This indicates slight differences in
ONPP due to resolution. Regions where ONPP
using Chlor a_2, Chlor_MODIS, SeaWiFS, and 4.6 km
are greater than with Chlor_a_3 are shaded
yellow. Differences between using 4.6 km equal
area inputs versus 39 km remapped data are less
than 1 GT total, and usually about 0.1 GT between
regions. Differences between SeaWiFS input and
MODIS Chlor_a_2, which include the resampling
errors, are on the same order. This suggests
that for carbon modeling, there are insignificant
differences between the two sensors. We recommend
that modelers use Chlor_a_3 and the 4.6 km ONPP
for comparisons with reality.
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• CONCLUSIONS
• 1. Differences in Global ONPP between SeaWiFS
  and MODIS (Chlor_a_2) are very slight in this
  study. Larger differences exist between OPP
  algorithms, or between Chl inputs.
• 2. Chlor_a_3 shows improved performance, nearly
  2x OPP in S. O., with phase differences.
• 3. Differences in phase and magnitude between
  P1, P2 relate to MLD, semi-analytic chlorophyll.
• 4. Higher OPP with MODIS, esp in high latitudes,
  represents a redistribution of global OPP
  patterns from earlier studies. The increase is
  comparable to the annual anthropogenic input, in
  terms of magnitude.
• 5. A SeaWiFS chlor_a_3 product would be useful.
  
• 6. Further validation of MODIS bio-optics and
  ONPP algorithms, is needed. Working Group
  activities are underway.

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