Transcript Monday_9_Kahru_Errors_in_sat_NPP_ICESOCC_2014-09-22.pptx

Errors in satellitederived NPP and EF
Mati Kahru
Scripps Institution of Oceanography/
University of California San Diego
La Jolla, CA 92093-0218
[email protected]
09/22/2014
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We have countless NPP algorithms but very few publicly available in situ
NPP datasets to evaluate those algorithms with real satellite data
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We need a publicly available NPP dataset to evaluate algorithms in the
SO! Currently only available: Saba et al. 2011  PPARR4 dataset with
585 stations from SO. Thanks, Vincent!
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Only a few satellite-derived NPP datasets publicly available: OSU
VGPM and CBPM. We need more to be publicly available in order to
make meaningful comparisons. It is not enough to compare 2 images and
state the differences! Why?
Laws et al. 2000: ef = f(NPP, SST)
Laws et al. 2011: Comparison of
observed and calculated ef-ratios
from Laws et al. (2000)(Δ) and
Dunne et al. (2005)(*).
Laws et al. 2011: Fig. 4. ef-ratios for fall 1997, winter 1998, spring 1998,
summer 1998.
Henson et al. 2011: estimating
ThE-ratio from SST only
ThE-ratio 
EF 
Maiti et al. 2013; Fig 2a.
EZ-Ratio, Siegel et al. 2014; unitless
E-ratio, Henson et al. 2011
Export Flux at 100 m, annual mean, Henson et al. 2011
Export Flux, annual mean, Siegel et al. 2014; TotEz (mgC m^-2 d^-1)
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NPP
TotEz
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NPP, totEz, mg m-2 day-
NPP and TotEz, Siegel et al. 2014; mean for 40-50 S,
based on 10 years of SeaWiFS data
EF, mg C m-2 day-1, mean for South of 50S; NPP-SPGANT * 0.725*Laws
EF, mgC m-2 day-1
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C:\SatProjects\SO\2012\2012_SO_EF\EfLaws0.725Merged_SouthOf50S.xlsx
NPP and TotEz, Siegel et al. 2014; mean for 40-50 S
NPP
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TotEz
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NPP, TotEz, mg m-2 day-1
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Ez, mg m-2 day-1
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AlgEz
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FecEz
TotEz
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C:\SatProjects\SO\2012\2012_SO_EF\EfLaws0.725Merged_SouthOf50S.xlsx
Western Antarctic Peninsula
VGPM MODISA
R2 = 0.41
MRPE = -51% for NPP, -52% for Chla
Better algorithm may not be better
when applied to real satellite data!
CBPM MODISA
R2 = 0.19
MRPE = 5%
AMLR region of Scotia Sea
C:\SatProjects\SO\2009\2009_match-ups matchups_1day.png
Errors in algorithm
components may reduce the
algorithm value with real
satellite data!
Multi-year Chl-a match-ups in the AMLR area of
the Scotia Sea
PPARR4 SO PAR matchups with MODISA 4-km PAR
C:\SatProjects\SO\2009\2009_match-ups matchups_1day.png
Inter-sensor comparison of satellite-derived Rrs443 (remote
sensing reflectance at 443 nm) in 2004 (C, D - Jan-2004)
SeaWiFS/MODISA
MERIS/MODISA
SeaWiFS/MODISA-L2
Rrs443/Rrs443
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
-2.8
From Kahru et al. 2013
-2.6
-2.4
-2.2
Log10 (Rrs443)
-2
Thank you!