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Ocean Color Chlorophyll (OC) v6

updated 18 Mar 2010, OC4O modified to use 516 instead of 520 nm



The operational algorithm for deriving near-surface chlorophyll-a concentrations (OC; O'Reilly et al. 2000) was updated using in situ data from NOMAD version 2. NOMAD is a publicly available, global bio-optical data set constructed from data archived in SeaBASS. The data span a wide range of water types from coastal and offshore regions and were collected by participants in the NASA Ocean Biology & Biogeochemistry Program and by voluntary and international collaborators. The algorithm form describes the polynomial best fit that relates the log-transformed geophysical variable to a log-transformed ratio of remote-sensing reflectances. The polynomial form is consistent with past versions of OC.


requirements

* polynomials bisect the full dynamic range of the development data set
* OC4 = OC4E = OC4O = OC3S = OC3M = OC3C = OC3E = OC3O = OC2S = OC2M = OC2E = OC2O


algorithm

form:

* Rrs1 = blue wavelength Rrs (e.g., 443, 490, or 510-nm)
* Rrs2 = green wavelength Rrs (e.g., 547, 555, or 565-nm)
* X = log10(Rrs1 / Rrs2)
* chlor_a = 10^(a0 + a1*X + a2*X^2 + a3*X^3 + a4*X^4)

changes from operational:

* none, simply a revised fit to an updated in situ data set

v6 coefficients:

sensordefault *bluegreena0a1a2a3a4
OC4 SeaWiFSY443>489>5105550.3272-2.99402.7218-1.2259-0.5683
OC4EMERISY443>489>5105600.3255-2.76772.4409-1.1288-0.4990
OC4OOCTSY443>489>5165650.3325-2.82783.0939-2.0917-0.0257
OC3SSeaWiFSN443>4895550.2515-2.37981.5823-0.6372-0.5692
OC3M-551MODISN443>4895500.2424-2.58281.7057-0.3415-0.8818
OC3M-547MODISY443>4895470.2424-2.74231.8017 0.0015-1.2280
OC3VVIIRSY443>4865500.2228-2.46831.5867-0.4275-0.7768
OC3EMERISN443>4895600.2521-2.21461.5193-0.7702-0.4291
OC3OOCTSN443>4895650.2399-2.08251.6126-1.0848-0.2083
OC3CCZCSY443>5205500.3330-4.37707.6267-7.1457 1.6673
OC2SSeaWiFSN4895550.2511-2.08531.5035-3.17470.3383
OC2EMERISN4895600.2389-1.93691.7627-3.0777-0.1054
OC2OOCTSN4895650.2236-1.82961.9094-2.9481-0.1718
OC2M-551MODISN4895500.2481-2.29581.4053-3.12990.6478
OC2M-547MODISN4895470.2500-2.47521.4061-2.82330.5405
OC2M-HIMODIS (500-m)Y4695550.1464-1.79530.9718-0.8319-0.8073
* Y indicates operational / default algorithm for each sensor within OBPG processing


algorithm development

OC4 OC3S OC3M-551 OC3M-547
OC4E OC4O OC3E OC3O
OC3V OC3C OC2S OC2E
OC2O OC2M-551 OC2M-547 OC2M-HI


algorithm verification: internal consistency

intercomparison of operational/default algorithms


intercomparison of 3-band algorithms


intercomparison of 2-band algorithms



algorithm verification: comparison with previous versions

operational OC4 and OC3M are v4 (SeaBAM); operational OC3S is v5 (NOMAD v1)




algorithm verification: comparison with Morel and Maritorena 2001




algorithm verification: level-2 match-ups

used NOMAD-free subset of SeaWiFS and MODIS-Aqua match-ups


SeaWiFS MODIS-Aqua


Questions? Contact Jeremy Werdell
NASA Ocean Biology Processing Group


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Authorized by: gene carl feldman

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Updated: 09 August 2013