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MODIS O CEAN N ET P RIMARY P RODUCTION ( ONPP )

MODIS O CEAN N ET P RIMARY P RODUCTION ( ONPP ). W.E. Esaias, NASA GSFC K.R.TURPIE, D. THOMAS, R. VOGEL, A. BHATTI September 5, 2003 Oregon State University wayne.e.esaias@nasa.gov http://oppscf.gsfc.nasa.gov http://modis-ocean.gsfc.nasa.gov. Primary Productivity Round Robin.

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MODIS O CEAN N ET P RIMARY P RODUCTION ( ONPP )

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  1. 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@nasa.gov http://oppscf.gsfc.nasa.gov http://modis-ocean.gsfc.nasa.gov

  2. Primary Productivity Round Robin Campbell et al., GBC (2002)

  3. Estimates of Primary Productivity Most of the variability in estimates is due to the uncertainty in the physiological parameters in the models

  4. MODIS Ocean Net Primary Productionprovides measure of C fixation by phytoplanktonW.E. Esaias, NASA GSFCK.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

  5. 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

  6. 2000 2001 2002 Valid period 305-800

  7. 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 n=1.6K vs 0.759 n>4.5K Semi-analytic Chlor_a_3 shows improvement r2 = 0.784 Chlor-MODIS Chlor_a_2 Chlor_a_3 Watson Gregg & Nancy McCabe

  8. Level 3 Matchups

  9. 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

  10. 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 50°S 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 50°S 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.

  11. 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 Clark’s empirical algorithm Chlor_a_3 is Carder’s semi-analytic algorithm; it includes CDOM and pigment packaging corrections.

  12. 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.

  13. OPP STD PRODUCTS Figure 6. MODIS Terra ONPP, Mixed Layer Depth (red), and PAR (light blue) for oceans and subregions. P1 is the Behrenfeld-Falkowski VGPM (Black), P2 is Howard-Yoder Mixed Layer model (Blue). Both use Chlor_a_3 as the MODIS chlorophyll input in the operational archived product.

  14. OPP P2, 4 Chlorophylls Figure 8. ONPP - P2 (H-Y) 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.

  15. 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.

  16. 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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