Ocean Color Chlorophyll (OC) v6
For a more up to date version, please go here.
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:
sensor | default * | blue | green | a0 | a1 | a2 | a3 | a4 | |
---|---|---|---|---|---|---|---|---|---|
OC4 | SeaWiFS | Y | 443>489>510 | 555 | 0.3272 | -2.9940 | 2.7218 | -1.2259 | -0.5683 |
OC4E | MERIS | Y | 443>489>510 | 560 | 0.3255 | -2.7677 | 2.4409 | -1.1288 | -0.4990 |
OC4O | OCTS | Y | 443>489>516 | 565 | 0.3325 | -2.8278 | 3.0939 | -2.0917 | -0.0257 |
OC3S | SeaWiFS | N | 443>489 | 555 | 0.2515 | -2.3798 | 1.5823 | -0.6372 | -0.5692 |
OC3M-551 | MODIS | N | 443>489 | 550 | 0.2424 | -2.5828 | 1.7057 | -0.3415 | -0.8818 |
OC3M-547 | MODIS | Y | 443>489 | 547 | 0.2424 | -2.7423 | 1.8017 | 0.0015 | -1.2280 |
OC3V | VIIRS | Y | 443>486 | 550 | 0.2228 | -2.4683 | 1.5867 | -0.4275 | -0.7768 |
OC3E | MERIS | N | 443>489 | 560 | 0.2521 | -2.2146 | 1.5193 | -0.7702 | -0.4291 |
OC3O | OCTS | N | 443>489 | 565 | 0.2399 | -2.0825 | 1.6126 | -1.0848 | -0.2083 |
OC3C | CZCS | Y | 443>520 | 550 | 0.3330 | -4.3770 | 7.6267 | -7.1457 | 1.6673 |
OC2S | SeaWiFS | N | 489 | 555 | 0.2511 | -2.0853 | 1.5035 | -3.1747 | 0.3383 |
OC2E | MERIS | N | 489 | 560 | 0.2389 | -1.9369 | 1.7627 | -3.0777 | -0.1054 |
OC2O | OCTS | N | 489 | 565 | 0.2236 | -1.8296 | 1.9094 | -2.9481 | -0.1718 |
OC2M-551 | MODIS | N | 489 | 550 | 0.2481 | -2.2958 | 1.4053 | -3.1299 | 0.6478 |
OC2M-547 | MODIS | N | 489 | 547 | 0.2500 | -2.4752 | 1.4061 | -2.8233 | 0.5405 |
OC2M-HI | MODIS (500-m) | Y | 469 | 555 | 0.1464 | -1.7953 | 0.9718 | -0.8319 | -0.8073 |
* Y indicates operational / default algorithm for each sensor within OBPG processing
algorithm development
OC4 | OC3S | OC3M-551 | OC3M-547 |
---|---|---|---|
[](ocfit_oc4.png) | [](ocfit_oc3s.png) | [](ocfit_oc3m.png) | [](ocfit_oc3mr.png) |
[](ocdens_oc4.png) | [](ocdens_oc3s.png) | [](ocdens_oc3m.png) | [](ocdens_oc3mr.png) |
OC4E | OC4O | OC3E | OC3O |
---|---|---|---|
[](ocfit_oc4e.png) | [](ocfit_oc4o.png) | [](ocfit_oc3e.png) | [](ocfit_oc3o.png) |
[](ocdens_oc4e.png) | [](ocdens_oc4o.png) | [](ocdens_oc3e.png) | [](ocdens_oc3o.png) |
OC3V | OC3C | OC2S | OC2E |
---|---|---|---|
[](ocfit_oc3v.png) | [](ocfit_oc3c.png) | [](ocfit_oc2s.png) | [](ocfit_oc2e.png) |
[](ocdens_oc3v.png) | [](ocdens_oc3c.png) | [](ocdens_oc2s.png) | [](ocdens_oc2e.png) |
OC2O | OC2M-551 | OC2M-547 | OC2M-HI |
---|---|---|---|
[](ocfit_oc2o.png) | [](ocfit_oc2m.png) | [](ocfit_oc2mr.png) | [](ocfit_oc2mh.png) |
[](ocdens_oc2o.png) | [](ocdens_oc2m.png) | [](ocdens_oc2mr.png) | [](ocdens_oc2mh.png) |
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 |
---|---|
[](ocval_swf.png) | [](ocval_mod.png) |
NASA Ocean Biology Processing Group