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 &amp 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_sm.png)](ocfit_oc4.png) [![](ocfit_oc3s_sm.png)](ocfit_oc3s.png) [![](ocfit_oc3m_sm.png)](ocfit_oc3m.png) [![](ocfit_oc3mr_sm.png)](ocfit_oc3mr.png)
[![](ocdens_oc4_sm.png)](ocdens_oc4.png) [![](ocdens_oc3s_sm.png)](ocdens_oc3s.png) [![](ocdens_oc3m_sm.png)](ocdens_oc3m.png) [![](ocdens_oc3mr_sm.png)](ocdens_oc3mr.png)

OC4E OC4O OC3E OC3O
[![](ocfit_oc4e_sm.png)](ocfit_oc4e.png) [![](ocfit_oc4o_sm.png)](ocfit_oc4o.png) [![](ocfit_oc3e_sm.png)](ocfit_oc3e.png) [![](ocfit_oc3o_sm.png)](ocfit_oc3o.png)
[![](ocdens_oc4e_sm.png)](ocdens_oc4e.png) [![](ocdens_oc4o_sm.png)](ocdens_oc4o.png) [![](ocdens_oc3e_sm.png)](ocdens_oc3e.png) [![](ocdens_oc3o_sm.png)](ocdens_oc3o.png)

OC3V OC3C OC2S OC2E
[![](ocfit_oc3v_sm.png)](ocfit_oc3v.png) [![](ocfit_oc3c_sm.png)](ocfit_oc3c.png) [![](ocfit_oc2s_sm.png)](ocfit_oc2s.png) [![](ocfit_oc2e_sm.png)](ocfit_oc2e.png)
[![](ocdens_oc3v_sm.png)](ocdens_oc3v.png) [![](ocdens_oc3c_sm.png)](ocdens_oc3c.png) [![](ocdens_oc2s_sm.png)](ocdens_oc2s.png) [![](ocdens_oc2e_sm.png)](ocdens_oc2e.png)

OC2O OC2M-551 OC2M-547 OC2M-HI
[![](ocfit_oc2o_sm.png)](ocfit_oc2o.png) [![](ocfit_oc2m_sm.png)](ocfit_oc2m.png) [![](ocfit_oc2mr_sm.png)](ocfit_oc2mr.png) [![](ocfit_oc2mh_sm.png)](ocfit_oc2mh.png)
[![](ocdens_oc2o_sm.png)](ocdens_oc2o.png) [![](ocdens_oc2m_sm.png)](ocdens_oc2m.png) [![](ocdens_oc2mr_sm.png)](ocdens_oc2mr.png) [![](ocdens_oc2mh_sm.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_sm.png)](ocval_swf.png) [![](ocval_mod_sm.png)](ocval_mod.png)

Questions? Contact Jeremy Werdell
NASA Ocean Biology Processing Group